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Journal of Archaeological Science 36 (2009) 1910–1921

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Journal of Archaeological Science

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Towards the identification of dyestuffs in Early Iron Age Scandinavianpeat bog textiles

I. Vanden Berghe a,*, Margarita Gleba b, Ulla Mannering b

a Royal Institute for Cultural Heritage (KIK/IRPA), Jubelpark 1, B-1000 Brussels, Belgiumb The Danish National Research Foundation’s Centre for Textile Research, University of Copenhagen, 102 Njalsgade, 2300 Copenhagen S, Denmark

a r t i c l e i n f o

Article history:Received 7 November 2008Received in revised form8 April 2009Accepted 26 April 2009

Keywords:Natural organic dyesDye extractionHigh performance liquid chromatographyArchaeological textilesScandinaviaEarly Iron Age

* Corresponding author. Tel.: þ32 2 739 6846; fax:E-mail address: ina.vandenberghe@kikirpa.be (I. V

0305-4403/$ – see front matter � 2009 Elsevier Ltd.doi:10.1016/j.jas.2009.04.019

a b s t r a c t

A large systematic dye investigation of prehistoric Danish and Norwegian bog textiles was carried outusing high performance liquid chromatography with photo diode array detection. After the selection ofthe most suitable protocol for dye extraction and HPLC analysis for this specific group of archaeologicalsamples, the second part included the characterisation of the dyes detected in the whole series of theEarly Iron Age textiles and the interpretation of the dyeing technology. Natural organic dyes were foundfrom the three main categories of natural dyes, hence throwing new light on the use of biological dyesources in Early Iron Age Scandinavia. The results clearly indicate that most Scandinavian peat bogtextiles originally were dyed and that already during the 1st millennium BC, the populations in Scan-dinavia were familiar with the dyeing technology.

� 2009 Elsevier Ltd. All rights reserved.

1. Introduction

Ancient textiles are rare finds in archaeology but, in Scandinavia,wet, acidic, low oxygen or completely anoxic conditions and thepresence of polysaccharide sphagnan in the peat bogs (Painter,1995, 1998; van der Sanden, 1996, 18) have preserved a largenumber of prehistoric textiles (Hald, 1980; Mannering and Gleba,forthcoming). Most of these finds date to the Scandinavian EarlyIron Age (500 BC–AD 400), when the custom of depositing objectsin the bogs was practiced by the prehistoric inhabitants of thisregion. The majority of textiles have been found in Denmark (Hald,1980). Two finds are known from Norway (Halvorsen, forthcoming)and one from Sweden (Franzen et al., forthcoming). Most objectswere found in the 19th and the first half of the 20th century, whenpeat was excavated as heating material.

The bog textiles constitute one of the largest and best-preservedcollections of prehistoric textiles in existence. In 2006, the DanishNational Research Foundation’s Centre for Textile Research initi-ated the research program ‘Textile and Costume from Bronze andEarly Iron Ages in Danish Collections’ in order to examine the entirecorpus of Danish bog textiles. The study of Danish bog findswarranted a closer look at the question of DYEING in Early Iron AgeScandinavia.

þ32 2 732 0105.anden Berghe).

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A wide variety of plant and animal sources are known aspotential sources for the production of textile dyes (Cardon, 2007).The most practical way to classify the natural organic dyes is on thebasis of the methods of their application. In this respect, three maincategories are to be distinguished as the direct, the vat and themordant dyes. Direct dyes are water-soluble and have affinity forfibres in the dye bath. Within this group, well-known dyes are orchiland saffron. Vat dyes are not soluble in water. Prior to the dyeing,they are reduced into the water-soluble leuco-form to impregnatethe textile. Once in the fibre, they are brought back to their insolubleform by oxidation. Indigo, woad and Tyrian purple belong to thisgroup. Most natural organic dyes however are mordant dyes.Although they are soluble in water, they have no affinity for the fibre.A mordant, which can be either a tannin or a soluble metal salt, isrequired for the binding of the dye to the fibre. The type of mordantapplied will determine the final colour of the dyed fabric. Thus,madder dyed in the presence of alum will produce a bright redcolour, while a violet shade will be obtained by using iron.

While several studies of organic dyes found in Scandinavianarchaeological textiles have been reported during the 1980s(Bender Jorgensen and Walton, 1986; Walton, 1986, 1988), untilnow it was considered that the earliest dyed fabrics in Scandinaviawere the blanket from the Danish bog at Skærsø (Østergaard, 1994),dated to the 1st century BC and textile fragments from the Danishburial at Lønne Hede, dated to the 1st century AD (Walton, 1986).Furthermore, Scandinavian dyeing technology has been largely

Vanden Berghe, T. et al. / Journal of Archaeological Science 36 (2009) 1910–1921 1911

connected to Roman influences in Northern Europe and themajority of extant analyses have been performed on the finds datedto the Roman Iron Age (AD 1–400) (Walton Rogers, 1995).

The first part of the study was dedicated to the selection of themost suitable protocol for dye extraction and HPLC analysis for thisspecific group of archaeological samples. Several different recentlypublished soft extraction methods and methods showing improvedsensitivity were evaluated, first on references, later on a limited setof archaeological samples. One of these methods was chosen for theanalysis of the complete series of the Early Iron Age textiles.

Fig. 1. . Geographical position of the Scandinavian sites.

2. Materials and methods

2.1. Sources of samples and their description

Due to the long sojourn in the tannin-rich peat bog environ-ment, the present colours of the textiles vary from light brown toreddish brown to almost black. Although several textiles actuallystill have reddish and greenish shades suggesting the use of dyeing,it is no longer possible to identify the original colour visually orunder the microscope. In some cases the colours are evenmisleading: thus, in the Bredmose scarf (sample 181), the reddishyarn, creating a grid check pattern tested positive for indigotin.Only in the case of one find, the band from Huldremose I (sample144), the present greenish brown colour suggested the originalpresence of blue dye. Furthermore, the majority of these fabrics arepatterned with checks or stripes, achieved by using differentnaturally pigmented wools. Therefore, in this study both warp andweft yarns were sampled in each case (designated system A and Bwhen warp and weft direction could not be determined) and allthreads of differing colours were tested, i.e. at least two sampleswere analysed for each textile.

2.1.1. Danish archaeological textilesThe samples analysed were taken from the textiles found in peat

bogs on 27 sites, mainly on Jutland peninsula (Fig. 1). The majorityof the finds are now in the collections of the National Museum ofDenmark, but individual finds are also in the museums at Randers,Viborg, Års, Kolding, Silkeborg and Ålborg. They are all dated to theScandinavian Early Iron Age (500 BC–AD 400). Only two of the findswere previously tested, however using a different method (Walton,1988).

2.1.2. Norwegian archaeological textilesThe samples come from the finds recovered at the sites of Tegle

and Helgeland in southern Norway (Fig. 1), currently in thecollection of the Stavanger Museum. Only a selection of sampleswas provided and analysed, however they should be representativefor these finds. Both finds are dated to the Scandinavian Migrationperiod (AD 400–575).

2.2. Technique

2.2.1. High performance liquid chromatographyPrevious organic dye studies of archaeological samples from

Danish textiles were performed with UV/visible spectrophotometryafter dye extraction, followed by confirmation with paper and thin-layer chromatography (Walton, 1986, 1988). In the present study,high performance liquid chromatography (HPLC) was used. Foreach component eluting the column at a specific retention time, thecharacteristic UV-visible spectra are recorded with the help ofa photo diode array detection system (DAD). Identification of dyecomponents is done by comparison of both retention time and thespectral data of the sample with those from a reference database.

Although this technique has proven its efficiency for thedetection of natural organic dyes in archaeological textiles froma wide historical and geographical context (Cardon et al., 2004;Hofmann-de Keijzer et al., 2005; Nowik et al., 2005; Szotek et al.,2003; Vanden Berghe and Wouters, 2004a,b; Wouters, 1998;Wouters and Rosario-Chirinos, 1992; Zhang et al., 2008), the anal-ysis of archaeological finds imposes particular challenges. Envi-ronmental processes before and during excavation, interactionsbetween the objects of study and other finds in direct or indirectcontact with them, different stages of degradation of the textile orpseudomorph itself and of the surrounding materials, the mutualinfluences of the occurring degradation reaction mechanism arejust some of the major external factors that will have influence onthe actual state of the textiles and dyes.

2.2.2. Improvement of the analytical protocolThe amount of dyes left on archaeological textiles is usually very

low. Preliminary dye analyses on a small set of samples showed thatonly very small peaks were found mainly referring to flavonoid dyecomponents. These tests were done using acidic methanol extrac-tion, a well-known method for the detection of a wide range of dyeconstituents belonging to the main three groups of natural colorants,the anthraquinone, flavonoid and indigoid dyes (Wouters, 1985).

In order to improve the sensitivity of the analysis method withrespect to archaeological bog samples, a second analytical protocolwas applied using acidic methanol extraction, followed by a secondextraction in ethyl acetate (EtAc). Based on previous studies onarchaeological textiles from Verucchio, Italy (700–640 BC) (VandenBerghe, 2002) and Bucovina County in Romania (14–15th centuryAD) (Petroviciu et al., forthcoming), this method proved to be verysensitive for dye extraction in very contaminated samples. Especially

Vanden Berghe, T. et al. / Journal of Archaeological Science 36 (2009) 1910–19211912

for flavonoids, other extraction methods, giving higher extractionyields and preserving the glycosidic linkages, were evaluated as well.Two soft extraction methods using ethylenediaminetetraacetic acid(EDTA) and formic acid have been reported recently to be very effi-cient in extracting dyes, while only causing minor or no decompo-sition of the glycosides (Zhang and Laursen, 2005). The formic acidmethod gave a better efficiency for anthraquinone dyes extractedfrom silk, while extraction with EDTA was preferable in the case offlavonoids. The last protocol tested was acidic methanol extractionfollowed by a consecutive extraction in dimethylformamide (DMF).Applied on newly dyed wool samples, as well as on historical wooltextiles from Scottish bog costumes, this method was reported togive a better efficiency for a lot of flavonoids, indigotin and someanthaquinones (Surowiec et al., 2006).

3. Experimental

Each dye analysis requires a sample between 0.2 and 0.5 mg.After pre-examination under binocular to avoid visible contami-nation, the dyes were extracted from the yarn using one of thefollowing extraction methods.

3.1. Extraction method 1 (code Acid. MeOH) (Wouters, 1985)

To the sample of yarn, 250 ml water/methanol/37% hydrochloricacid (1/1/2, v/v/v) is added. The mixture is heated for 10 min at105 �C in open Pyrex tubes in a heating block. After cooling it isfiltered through a porous polyethylene frit. The clear filtrate is driedin an evacuated desiccator over NaOH pellets. The dry residues aretaken up in 50 ml methanol/water (1/1, v/v) and 20 ml of this solu-tion is injected for analysis.

3.2. Extraction method 2 (code Acid. MeOH/DMF)(Surowiec et al., 2006)

To the sample of yarn, 400 ml water/methanol/37% hydrochloricacid (1/1/2, v/v/v) is added. The mixture is heated for 10 min at105 �C in open Pyrex tubes in a heating block. After rapid coolingdown under tap water, the extract is dried in an evacuated desic-cator over NaOH pellets. The dry residues are taken up in 400 mlmethanol/dimethyl formamide (1/1, v/v) and heated for 5 min at105 �C, followed by rapid cooling down and filtering througha porous polyethylene frit. The filtrate is evaporated in an evacuateddesiccator over NaOH pellets. The dry residues are taken up in 50 mlmethanol/water (1/1, v/v) and 20 ml of this solution is injected inthe chromatograph.

3.3. Extraction method 3 (code Acid. MeOH/EtAc)

To the sample of yarn, 500 ml water/methanol/37% hydrochloricacid (1/1/2, v/v/v) is added. The mixture is heated for 10 min at105 �C in open Pyrex tubes in a heating block. After rapid coolingunder tap water, the solution is extracted a second time by adding1000 ml ethyl acetate. After decanting of the upper phase, this ethylacetate solution is evaporated in an evacuated desiccator overNaOH pellets. The dry residues are taken up in 50 ml methanol/water (1/1, v/v) and 20 ml of this solution is injected in thechromatograph.

3.4. Extraction method 4 (code H2EDTA) (Zhang and Laursen, 2005)

To the sample of yarn, 200 ml of 0.001 M H2EDTA/acetonitrile/methanol (2/10/88, v/v/v) solution is added. The mixture is heatedfor 30 min at 60 �C in closed Pyrex tubes in a heating block. Aftercooling down at room temperature the extract is evaporated in an

evacuated desiccator over NaOH pellets. The dry residues are takenup in 50 ml methanol/water (1/1, v/v). After centrifuging of thesolution, 20 ml of upper phase of this solution is taken for injectionin the chromatograph.

3.5. Extraction method 5 (code HCOOH) (Zhang and Laursen, 2005)

To the sample of yarn, 200 ml formic acid/methanol (5/95, v/v) isadded. The mixture is heated for 30 min at 40 �C in closed Pyrextubes in a heating block. After cooling down at room temperaturethe extract is evaporated in an evacuated desiccator over NaOHpellets. The dry residues are taken up in 50 ml methanol/water (1/1,v/v). After centrifuging of the solution, 20 ml of upper phase of thissolution is taken for injection in the chromatograph.

3.6. Chromatographic conditions

The HPLC equipment consists of a high-pressure pump (ModelM615, Waters, USA), a photo diode array detector (Model 996,Waters, USA) and a system for data storage, manipulation andretrieval (Empower, Waters, USA).

For the extraction methods using acidic methanol alone or incombination with a second extraction (methods 1–3), the samechromatographic conditions were applied using a temperaturecontrolled (20–22 �C) Lichrosorb RP-18 column (4.0 � 125 mm,5 mm particle size, VWR, Belgium). Three solvents are used: (A)water; (B) methanol; and (C) 5% (w/v) phosphoric acid in water. Theelution program is 60A/30B/10C for 3 min, followed by a lineargradient to 10A/80B/10C for 26 min. A flow rate of 1.2 mL/min wasused (HPLC protocol 1).

The mild extraction methods, developed to optimise the detec-tion of flavonoid glycosides and degradation products (methods 4and 5), required the development of an adapted analytical protocol.A monomeric Grace Vydac DE C18 column (3.2 � 250 mm, 5 mmparticle size, Grace Devision, BE) was chosen providing very goodseparation of both small-molecule analytes as well as high molec-ular weight molecules such as glycosides. A flow rate of 0.4 mL/minwas used during the 50 min runtime. The solvent gradient wascomposed of: (A) acetonitrile for HPLC; (B) water; and (C) tri-fluoroacetic acid 0.1%. The elution program starts with a lineargradient for 20 min from 10A/70B/20C to 30A/70B/0C followed bya linear gradient to 60A/40B/0C for 20 min and an isocratic gradientfor 10 min (HPLC protocol 2).

Identification of the dye components was done by comparisonof the spectral data with the reference spectra in the KIK/IRPAdatabase (130 references) at the maximum absorbance wavelengthof each peak.

4. Results

4.1. Evaluation of the analytical protocols on archaeologicalbog samples

The results of the applied protocols on a small selection ofarchaeological bog textile samples are given in Table 1. Limitationsin sample size made it impossible to test all protocols on the samesample. Considering previous positive experiences with Acid.MeOH/EtAc extraction on archaeological samples, compared toAcid. MeOH alone, we chose to focus on the comparison of the firstmethod with the soft extraction methods. Evaluation of thedifferent extraction and HPLC methods was not straightforwardconsidering the minimal remains of dyes left on the samples,implying that any heterogeneity of the samples could influence theoutcome of the comparison.

Table 1Study of different analytical protocols applied on Scandinavian archaeological textiles.

Object ID/site Sample ID/description Codes extraction method Dye component(s) Derivates of Other

Benzoic acid Cinnamic acid

NM C24624Bredmose

04 dark warp Acid. MeOH/EtAc Luteolin, apigenin X –Acid. MeOH/DMF – – –

NM C25182 Ømark 11 coloured weft HCOOH – X –Acid. MeOH/EtAc – X X

NM 3707C2Haraldsær

13 dark warp HCOOH – X –Acid. MeOH/EtAc Luteolin, quercetin X –

NM C7649Stockholm

32 light weft HCOOH Luteolin X XAcid. MeOH/EtAc Luteolin X –

NM C26451Borremose I

95 system A HCOOH Luteolin X XH2EDTA – X XAcid. MeOH/EtAc Unknown 1 wlichen X –

NM C26451Borremose I

96 system B HCOOH – X XH2EDTA – X XAcid. MeOH/EtAc Unknown 1 wlichen X –

NM 7142A Fræer 97 warp HCOOH Luteolin X XH2EDTA Luteolin X XAcid. MeOH/EtAc Luteolin, apigenin X –

NM C3474Huldremose II

115 medium warp HCOOH Rhamnetin X XH2EDTA – X X Epigallo-catechinAcid. MeOH/EtAc Unknown 5 þ unknown 3 wlichen/

alkanninX X

NM C3474Huldremose II

118 medium weft HCOOH Rhamnetin X XH2EDTA Rhamnetin X XAcid. MeOH/EtAc Unknown 3 wlichen/(alkannin) X X

NM C3477Huldremose I

144 band Acid. MeOH Indigotin X –Acid. MeOH/EtAc Indigotin, indirubin, luteolin X – Ellagic acidAcid. MeOH/DMF Indigotin, indirubin – – Ellagic acid

NM D1310IKrogens Mølle

149 warp, coarse twill HCOOH – X –Acid. MeOH – X –Acid. MeOH/EtAc – X – Ellagic acidAcid. MeOH/DMF Indigotin – – Ellagic acid

NM D1310IKrogens Mølle

152 dark twill HCOOH Luteolin X XH2EDTA – X XAcid. MeOH – X –Acid. MeOH/EtAc – X – Ellagic acidAcid. MeOH/DMF Indigotin – – Ellagic acid

NM D1310IKrogens Mølle

153 system 1, tabby HCOOH – X XH2EDTA – X XAcid. MeOH/EtAc Indigotin X –

NM D12244Grathe Hede

159 reddish thread,system 1

HCOOH – X –Acid. MeOH/EtAc – X –

VSM 09374 Elling 174 weft Acid. MeOH – X –Acid. MeOH/EtAc Luteolin X – Ellagic acidAcid. MeOH/DMF Indigotin – – Ellagic acid

NM 7325c Corselitze 179 warp Acid. MeOH/EtAc Luteolin X –HCOOH Luteolin X XH2EDTA Luteolin X X

Extractions coded Acid. MeOH, Acid. MeOH/EtAc and Acid. MeOH/DMF are related to HPLC protocol 1; extraction methods HCOOH and H2EDTA to HPLC protocol 2.

Vanden Berghe, T. et al. / Journal of Archaeological Science 36 (2009) 1910–1921 1913

Most of the aglycones were found using the acidic methanolextraction followed by the ethyl acetate extraction in (MeOH/EtAc).For specific samples, flavonoids were found only with one of the mildextraction methods, but not detected with ethyl acetate. This was thecase with samples 95 from Borremose I and 152 from Krogens Mølle,where luteolin was only detected using the HCOOH method, whilefor samples 115 and 118 from Huldremose I, rhamnetin was observedtwice, in the warp only using HCOOH extraction and in the weft usingboth HCOOH and H2EDTA mild extractions. However, also theopposite occurred. The flavonoids in the Haraldskær sample 13 wereonly found by using MeOH/EtAc. The MeOH/DMF method proved tobe most useful for the detection of indigotin (samples 149 and 152,both from Krogens Mølle) but less efficient for flavonoids.

None of the dye protocols tested on the bog samples resulted inthe detection of glycosides and whatever the applied technique,components were still detected just above the detection limit of theanalysis. Considering the peak height of the detected dye

components (mainly focussing on luteolin) as well as the colour ofthe sample after extraction, best extraction of the dyes wasobtained by using the Acid. MeOH/EtAc extraction and analysisprotocol. A typical example of the outcome of the dye analyses ofa Danish bog textile (97) from Fræer Mose, analysed after HCOOHextraction using HPLC protocol 2 (Fig. 2A) and after Acid. MeOH/EtAc extraction using HPLC protocol 1 (Fig. 2A) is given in Fig. 2.

Although a better outcome for flavonoids or indigoids was foundin some occasions respectively using one of the soft extractions orthe MeOH/DMF method, the risk of loosing other categories ofconstituents remained very significant with these specific archaeo-logical samples. None of the investigated methods, applied on thistype of archaeological samples, could lead to a systematicimprovement of the dye analysis.

Considering that acidic methanol extraction followed by theethyl acetate treatment turned out to give the best dye extraction,leading to the detection of both flavonoid as indigoid dyes in

Abs

orpt

ionu

nits

(A

U, 2

55nm

)

A

B

0,000

0,002

0,004

Minutes5,00 10,00 15,00 20,00 25,00 30,00 35,00 40,00 45,00 50,00

dhb

phb

dhb’’ cin’ cin’’ lu (Rt 29,3)

259,2

294,7

254

259,2

221,6

282,9 202,9228,7278,1

Rt 29,3

259

295

Rt12,5

259

Rt13,8

222

283

Rt 16,4

203229

278

Rt 18,1

254349

dhb phb dhb’’ cin’ cin ’’ lu

Rt8,5300 700nm300 700nm300 700nm300 700nm300 700nm300 700nm

AU

0,015

0,020

0,025

0,030

0,035

0,040

Minutes10,00 12,00 14,00 16,00 18,00 20,00 22,00 24,00 26,00 28,00 30,00

lu (Rt15,2)

Abs

orpt

ionu

nits

(A

U, 2

55nm

)

wavelength (nm)200 300 400 500 600 700

251 350

AU

luteolin spectra

Tx97 / Ref.

Fig. 2. HPLC-DAD analysis of warp thread (97) from bog textile from Fræer Mose (110 BC–AD 60): chromatograms (integration at 255 nm) and UV-Vis absorbance spectra afterHCOOH extraction and HPLC protocol 2 (ACN/water/TFA gradient) (A) and after Acid. MeOH/EtAc extraction and HPLC protocol 1 (water/MeOH/H3PO4 gradient) (B); Detectedcomponents: luteolin (lu); 3,4-dihydroxybenzoic acid (dhb) and derivative of dhb (dhb0); para-hydroybenzoic acid (phb) and derivatives of cinnamic acid (cin0 , cin00).

Vanden Berghe, T. et al. / Journal of Archaeological Science 36 (2009) 1910–19211914

several analyses and that it was the only technique showingconstituents suggesting the use of lichen dyes, the last method wasselected for the analysis of the complete series of peat bog textiles.

4.2. Results of dye analysis of Scandinavian bog textiles

An overview of the identified dye components on the Scandi-navian bog textiles, for each site, is given in Table 2. The individualsamples are listed in alphabetical order of the sites and according tothe object inventory number, sample number and description of itscolour and function. Radiocarbon dates for the finds are provided inbrackets (Halvorsen, forthcoming; Mannering et al., forthcoming).

In 80% of the analysed samples, traces of one or more dyecomponents were detected. Small peaks of luteolin were found onthe majority of the samples. Other, more rarely detected flavonoidswere apigenin, quercetin and rhamnetin. Although the actualcolour of the samples is varying from almost black to differentbrown and reddish/brown shades, red dye components were veryrare. Alizarin and purpurin were detected in only two textiles.Indigotin and indirubin were found as well, frequently in combi-nation with luteolin in the same textile. Since most of thesecompounds are not species specific and because dye sources areusually composed of many different characteristic dye components,only few of which survived over time in these prehistoric samples,

species identification is hardly possible. The dye results rathersuggest a specific range of dye sources.

4.2.1. Yellow dyesLuteolin (30,40,5,7-tetrahydroxyflavone) was found in two thirds

of the samples, occasionally in combination with other flavonoids.Apigenin (40,5,7-trihydroxyflavone) was detected seven times, whilea combination of luteolin with quercetin (3,30,40,5,7-pentahydroxy-flavone) was detected twice. Studies dealing with the photooxida-tion mechanism of the very light sensitive group of flavonoid dyes(Ferreira et al., 2002, 2003; Peggy, 2006) have shown that, amongthem, the flavones are the most stable constituents. However, thelack of knowledge about the degradation mechanism of theseconstituents in an oxygen and light free, humid environment doesnot allow at present any explanation of the predominance of luteolinas the main flavonoid component found in peat bog textiles. Thepreservative qualities of the bog environment, however, mayaccount for the higher degree of survival of luteolin in bogscompared to other archaeological contexts.

Possible luteolin-based yellow dye sources in a North Europeancontext are weld (Reseda luteola L.), sawwort (Serratula tinctoria L.),dyer’s broom (Genista tinctoria L.) or chamomile types (Anthemisspecies) (Cardon, 2007; Schweppe, 1993). As, apart from luteolinand occasionally apigenin, no other characteristic flavonoid

Table 2Dye components found in Scandinavian Early Iron Age peat bog textiles.

Object ID Sample ID Warp/weft Sample description HPLC-DAD detected dye components Applied extraction(s)

Ålestrup, Denmark (520–380 BC)VMÅ C183(4) 66 Warp Light brown Luteolin 1VMÅ C183(4) 67 Warp Dark brown Luteolin þ apigenin 1VMÅ C183(4) 68 Weft Light brown Luteolin 1VMÅ C183(4) 69 Weft Dark brown Luteolin 1VMÅ C183(6) 70 Warp Dark brown No dyes detected 1VMÅ C183(6) 71 Warp Light brown Luteolin 1VMÅ C183(6) 72 Weft Dark brown Luteolin 1VMÅ C183(6) 73 Weft Light brown Luteolin þ apigenin 1Auning, Denmark (200 BC–AD 140)KHM 233/74 74 Warp Dark brown, pigmented Luteolin 1KHM 233/74 75 Warp Light brown Luteolin 1KHM 233/74 76 Weft Dark brown, pigmented Luteolin 1KHM 233/74 77 Weft Light brown Luteolin 1Borremose I, Denmark (365–116 BC)NM C26451 95 Warp Dark brown, pigmented Luteolin þ unknown 1 (415) 1, 4, 5NM C26451 96 Weft Dark brown, pigmented Unknown 1 (415) 1, 4, 5Borremose II, Denmark (483–95 BC)NM C26441 86 Warp Light brown Luteolin 1NM C26441 87 Weft Light brown Luteolin 1NM C26441 156 Warp Light brown, shiny Luteolin 1NM C26441 157 Weft Light brown, shiny Luteolin 1NM C26442 84 Warp Medium brown, pigmented Luteolin 1NM C26442 85 Weft Medium brown, pigmented Luteolin 1NM C26443 90 Warp Light brown Luteolin 1NM C26443 91 Warp Light brown Luteolin 1NM C26443 92 Weft Light brown Luteolin 1NM C26443 93 Weft Light brown Luteolin 1Borremose III, Denmark (401–209 BC)NM C26454 88 Warp Medium warp Luteolin 1NM C26454 89 Weft Medium weft Luteolin 1Borremose V, Denmark (370–180 BC)VMÅ 832 C189 61 Warp Light brown Luteolin 1VMÅ 832 C189 62 Weft Light brown Luteolin 1VMÅ 832 C189 63 Sewing thread Dark brown, plied No dyes detected 1VMÅ 832 C189 64 Sewing thread Light brown, plied Luteolin 1VMÅ 832 C189 65 Darning thread Light brown Luteolin 1Bredmose, Denmark (370 BC–AD 10)NM C24623 101 Warp Light brown Luteolin þ unknown 2 (422) and unknown 4 (414) 1NM C24623 102 Warp Dark brown, pigmented Luteolin þ unknown 2 (422) and unknown 4 (414) 1NM C24623 103 Weft Light brown Luteolin þ unknown 2 (422) and unknown 4 (414) 1NM C24623 104 Weft Dark brown, pigmented Luteolin þ unknown 2 (422) and unknown 4 (414) 1NM C24624(1) 1 Weft Dark brown, pigmented Indigotin þ luteolin 1NM C24624(1) 2 Warp Light brown Luteolin 1NM C24624(1) 3 Weft Light brown Luteolin þ unknown 2 (422) 1NM C24624(1) 4 Weft Dark brown, pigmented Luteolin þ apigenin 1, 2NM C24624(2) 5 Weft Dark brown, pigmented Luteolin 1NM C24624(2) 6 Warp Light brown Luteolin þ a trace of unknown 2 (422) 1NM C24624(2) 7 Weft Light brown Luteolin þ unknown 2 (422) 1NM C24624 8 Sewing thread Light brown Luteolin þ unknown 2 (422) 1NM C24626 109 Sprang Light brown No dyes detected 1NM C24627 105 Warp Light brown Luteolin 1NM C24627 106 Warp Black, pigmented Luteolin 1NM C24627 107 Weft Light brown Luteolin 1NM C24627 108 Weft Black, pigmented Luteolin 1NM C24627 181 Warp Light reddish brown Indigotin 1Corselitze, Denmark (AD 210–410)NM 7325 a 41 Warp Dark brown, pigmented Luteolin 1NM 7325 a 42 Weft Dark brown, pigmented No dyes detected 1NM 7325 b 39 Warp Dark brown, pigmented Indigotin þ luteolin 1NM 7325 b 40 Weft Dark brown, pigmented Indigotin þ luteolin 1NM 7325c 179 Warp Reddish brown Luteolin 1, 4, 5NM 7325c 180 Weft Reddish brown Luteolin 1NM 7325x 177 Warp Light brown Luteolin 1NM 7325x 178 Weft Light brown Indigotin þ luteolin 1Elling, Denmark (380 BC–AD 10)VSM 09374 173 Warp Dark brown, pigmented? Luteolin 1VSM 09374 174 Weft Dark brown, pigmented? Indigotin þ luteolin þ ellagic acid 1, 2, 3VSM 09374 175 Sewing thread Dark brown, pigmented Luteolin 1VSM 09374 176 Sewing thread Light brown Luteolin 1Fræer, Denmark (110 BC–AD 60)NM 7142A 97 Warp Light brown Luteolin þ apigenin 1, 4, 5NM 7142A 98 Weft Light brown Luteolin 1

(continued on next page)

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Table 2 (continued )

Object ID Sample ID Warp/weft Sample description HPLC-DAD detected dye components Applied extraction(s)

NM 7142B 99 Warp Light brown Luteolin 1NM 7142B 100 Weft Light brown Luteolin þ apigenin 1Grathe Hede, Denmark (190 BC–AD 10)NM D12244(2) 128 System A Dark brown, pigmented No dyes detected 1NM D12244(2) 129 System A Light brown No dyes detected 1NM D12244(2) 130 System B Dark brown No dyes detected 1NM D12244(2) 131 System B Light brown Luteolin 1NM D12244(1) 158 System A Light brown Indigotin 1

182* Indigotin 1NM D12244(1) 159 System A Reddish brown No dyes detected 1, 4

183* No dyes detected 1NM D12244(1) 160 System B Dark brown Indigotin 1

184* No dyes detected 1Haraldskær, Denmark (347–42 BC)NM C37143 23 Sprang Dark reddish brown No dyes detected 1

125* Luteolin 1NM 3706 21 Warp Light brown Luteolin 1NM 3706 22 Weft Light brown Luteolin 1NM 3707 C1 121 System A Light brown No dyes detected 1NM 3707 C1 122 System A Black, pigmented No dyes detected 1NM 3707 C1 123 System B Light brown No dyes detected 1NM 3707 C1 124 System B Black, pigmented No dyes detected 1NM 3707 C2 12 Warp Light brown No dyes detected 1

17* Luteolin 1NM 3707 C2 13 Warp Dark brown, pigmented Luteolin þ quercetin 1, 4

15* Luteolin 119* Luteolin 1

NM 3707 C2 14 Weft Light brown No dyes detected 118* Luteolin þ ellagic acid 1

NM 3707 C2 16 Weft Dark brown, pigmented Luteolin 120* Luteolin 1

Huldremose I, Denmark (350–41 BC)NM C3473 169 Warp Light brown Indigotin þ luteolin þ unknown 5 (324) 1NM C3473 170 Warp Medium brown, pigmented Indigotin þ luteolin þ unknown 5 (324) 1NM C3473 171 Weft Light brown Indigotin þ luteolin þ unknown 5 (324) 1NM C3473 172 Weft Medium brown, pigmented Luteolin þ unknown 5 (324) 1NM C3474 114 Warp Light brown Unknown 5 (324) 1NM C3474 115 Warp Medium brown Unknown 5 (324) þ unknown 3 (503)/rhamnetin 1, 4, 5NM C3474 116 Warp Medium brown, pigmented Unknown 5 (324) þ unknown 3 (503) 1NM C3474 117 Weft Light brown Unknown 5 (324) þ unknown 3 (503) 1NM C3474 118 Weft Medium brown Unknown 3 (503)/rhamnetin 1, 4, 5NM C3474 119 Weft Medium brown, pigmented Unknown 3 (503) 1NM C3474 120 Warp Medium brown, thick Unknown 5 (324) þ unknown 3 (503) 1NM C3477 144 Warp Green-brown Indigotin þ indirubin þ ellagic acid þ luteolin 1, 2, 3Huldremose II, Denmark (350–30 BC)NM C3505 110 Warp Light brown Ellagic acid 1NM C3505 111 Warp Medium brown, pigmented Luteolin 1NM C3505 112 Weft Light brown Luteolin 1NM C3505 113 Weft Medium brown, pigmented No dyes detected 1Karlby, Denmark (200 BC–AD 140)NM D4854 43 Warp Black, pigmented No dyes detected 1NM D4854 44 Warp Light brown Luteolin 1NM D4854 45 Weft Black, pigmented Luteolin 1NM D4854 46 Weft Light brown No dyes detected 1Krogens Mølle, Denmark (399–181 BC)NM D1310A 24 Warp Medium brown Luteolin 1NM D1310A 25 Warp Dark brown, pigmented Luteolin 1NM D1310A 26 Weft Medium brown Luteolin 1NM D1310A 27 Weft Dark brown, pigmented No dyes detected 1NM D1310C 28 System A Medium brown Indigotin þ luteolin 1NM D1310C 29 System A Dark brown, pigmented Luteolin 1NM D1310C 30 System B Medium brown Indigotin 1NM D1310E 34 Warp Light brown Luteolin 1NM D1310E 35 Warp Dark brown, pigmented No dyes detected 1NM D1310E 36 Weft Light brown No dyes detected 1NM D1310E 37 Weft Dark brown, pigmented No dyes detected 1NM D1310E 38 Sewing thread Medium brown No dyes detected 1NM D1310I(1) 149 Warp Light brown Indigotin þ ellagic acid 1, 2, 3, 4NM D1310I(1) 150 Weft Light brown Luteolin 1NM D1310I(3) 151 Warp Dark brown, pigmented No dyes detected 1NM D1310I(3) 152 Weft Dark brown, pigmented Indigotin þ luteolin þ ellagic acid 1, 2, 3, 4, 5NM D1310I(4) 153 Warp Medium brown Indigotin 1, 4, 5NM D1310I(4) 154 Warp Dark brown, pigmented Luteolin 1NM D1310I(4) 155 Weft Medium brown Indigotin 1NM D 1310K 50 Warp Light brown Luteolin 1NM D1310K 51 Weft Light brown Indigotin þ luteolin 1

Vanden Berghe, T. et al. / Journal of Archaeological Science 36 (2009) 1910–19211916

Table 2 (continued )

Object ID Sample ID Warp/weft Sample description HPLC-DAD detected dye components Applied extraction(s)

NM D1310M 185 Warp Medium brown No dyes detected 1NM D1310M 186 Warp Dark brown, pigmentedNM D1310M 187 Weft Medium brownNM D1310M 188 Weft Dark brown, pigmentedNM D1310N 52 Warp Medium brown Luteolin 1NM D1310N 53 Warp Dark brown indigotin þ luteolin 1NM D1310N 54 Weft Medium brown Luteolin 1Ømark, Denmark (390–200 BC)NM C25182 9 Weft Light brown Luteolin 1NM C25182 10 Warp Light brown Luteolin 1NM C25182 11 Weft Light brown, stained No dyes detected 1, 4Rebild, Denmark (360–110 BC)ÅHM 4608(1) 55 Warp Dark brown, pigmented Indigotin þ luteolin 1ÅHM 4608(1) 56 Warp Medium brown Luteolin 1ÅHM 4608(1) 57 Weft Dark brown, pigmented Luteolin 1ÅHM 4608(1) 58 Weft Medium brown Luteolin 1ÅHM 4608(2) 59 Warp Dark brown, pigmented Luteolin 1ÅHM 4608(2) 60 Weft Dark brown, pigmented Luteolin 1Rønbjerg II, Denmark (360–50 BC)NM D2625h 161 Warp Light brown thick Luteolin 1NM D2625h 162 Warp Medium brown Luteolin 1NM D2625h 163 Warp Black, pigmented Luteolin 1NM D2625h 164 Warp Dark brown, pigmented Luteolin 1NM D2625h 165 Weft Light brown Luteolin 1NM D2625h 166 Weft Dark brown, pigmented Luteolin 1NM D2625h 167 Weft Reddish brown Luteolin þ apigenin 1NMD2625h 168 Weft Black, pigmented Luteolin 1Skærsø, Denmark (350 BC–AD 90)MKH 336 139 Warp Dark reddish brown Alizarin 1MKH 336 140 Weft Dark reddish brown Alizarin (contamination of warp?) 1MKH 336 141 Tablet Dark reddish brown No dyes detected 1MKH 336 142 Tablet Dark reddish brown No dyes detected 1MKH 336 143 Tassel Red-brown Alizarin þ purpurin 1Søgårds I, Denmark (352–51 BC)SMS634 A205 199 System A Light brown Luteolin and luteolin-like 1Søgårds II, Denmark (AD 130–340)SMS634 A402 78 Warp Medium brown Indigotin 1SMS634 A402 79 Warp Light brown Indigotin 1SMS634 A402 80 Finishing cord Dark bluish brown Indigotin þ indirubin 1SMS634 A402 81 Tie cord No dyes detected 1Stidsholt, Denmark (392–204 BC)NM 18472 132 Warp Dark brown, pigmented No dyes detected 1NM 18472 133 Warp Medium brown No dyes detected 1NM 18472 134 Warp Light brown No dyes detected 1NM 18472 135 Weft Medium brown No dyes detected 1Stokholm, Denmark (360–50 BC)NM C7649 31 Warp Light brown Luteolin 1NM C7649 32 Weft Light brown Luteolin 1, 4NM C7649 33 Weft Medium brown, pigmented Luteolin 1Thorup I, Denmark (360–50 BC)VSM 2381 136 Weft Light-medium brown Luteolin 1VSM 2381 137 Weft Light brown Luteolin 1VSM 2381 138 Warp Light brown Luteolin 1Thorup II, Denmark (400-200 BC)NM C27442 145 Warp Light brown Luteolin 1NM C27442 146 Warp Medium brown Luteolin 1NM C27442 147 Weft Light brown – 1NM C27442 148 Weft Medium brown Luteolin 1Unknown site (400–200 BC)NM u.nr 82 Warp Dark brown, pigmented No dyes detected 1NM u.nr 83 Weft Dark brown, pigmented No dyes detected 1Helgeland, Norway (AD 425–535)S5960a 196 Tablet weave Medium brown Luteolin, quercetin and trace of apigenin 1S5960a 197 Tablet weave Very light brown Luteolin and luteolin-like 1S5960c 198 System A Medium brown Indigotin 1Tegle, Norway (AD 445–545)S4850(1) 189 Warp Medium brown No dyes detected 1S4850(2) 190 Warp Reddish brown Alizarin and indigotin 1S4850(2) 191 Weft Reddish brown Alizarin and trace of purpurin 1S4850(3) 192 Warp Dark brown Alizarin and indigotin 1S4850(4) 193 Sprang Medium brown No dyes detected 1S4850(5) 194 Warp Dark brown No dyes detected 1S4850(6a) 195 Yarn Dark brown No dyes detected 1

1: Acid. MeOH/EtAc; 2: Acid. MeOH/DMF; 3: Acid. MeOH; 4: HCOOH; 5: H2EDTA; (): maximum VIS absorbance wavelength of unidentified components; *: second sampleanalysed. Remark: luteolin-like component: component with spectral data identical to luteolin but at deviating retention time.

Vanden Berghe, T. et al. / Journal of Archaeological Science 36 (2009) 1910–1921 1917

Vanden Berghe, T. et al. / Journal of Archaeological Science 36 (2009) 1910–19211918

components survived, no further specification of the yellow dyesource is possible.

Rhamnetin (3,30,40,5-tetrahydroxy-7-methoxyflavone), wasdetected twice in the scarf from Huldremose I. Rhamnetin isa characteristic component for dye sources from the Rhamnaceaefamily. Many Rhamnus species are among the possible sources.Some of them are native to Europe, like common buckthorn(Rhamnus cartharticus L.), while many others grow in Asia(Schweppe, 1993). They are known under many different commonnames, such as Persian, Avignon, yellow, buckthorn, French,German, Italian, Hungarian, Turkish or Greek berries (Hofenk deGraaff, 2004; Schweppe, 1993). While not all of the botanicalvarieties contain the same exact constituents, they all have themajor light fast component rhamnetin in common. Since antiquity,berries of different species were used for yellow dyeing. Unripeberries give a yellow coloration on alum mordanted wool, whileripe berries produce a green colour and in an overripe state a darkpurple red shade is obtained (Hofenk de Graaff, 2004).

4.2.2. Blue dyesIndigotin is found in 28 samples from 16 textiles. The isomere

indirubin is found twice together with indigotin. Both are thecharacteristic dye components referring to the use of an indigoiddye source. Theoretically, both indigo (Indigofera or Polygonumspecies) and woad (Isatis tinctoria L.) are possible dye sources ofthese constituents. However, in terms of historical and geograph-ical context of the textiles, woad is the most probable one, as theCentral Asian Indigofera-derived dye was not imported to NorthernEurope before the Renaissance period (Balfour-Paul, 1998).

There is only one textile where woad was found to be the onlyapplied dye source. In the textile from Søgårds Mose II, both the lightand dark warp threads as well as the finishing cord, all belonging tothe leg wrapper A, were dyed with woad, while the tie cord wasfound to be undyed (the weft could not be sampled due to theintactness of the item). In almost all other textiles, indigotin wasfound in combination with the flavonoid dye component, luteolin,indicating that green may have been the desired colour. Evidence ofwoad dyeing was also found in the analysed samples from Tegle andHelgeland, where it was detected once alone (sample 198) and twicein combination with alizarin, hence suggesting an original purplecolour of the warp threads from Tegle (samples 190 and 191).

4.2.3. Red dyesThe antraquinone component alizarin was identified in two

samples belonging to the same textile from Skærsø in Denmark,and three times in Tegle finds excavated in Norway. These are theonly textile fragments from the whole analysed collection, in whicha red dye source of the Rubiaceae family was identified, referring towell-known sources such as ladies bedstraw (Galium verum L.),dyer’s woodruff (Asperula tinctoria L.) or madder types (Rubiaspecies).

In the warp from the ground weave of the Skærsø find, alizarinwas detected alone, while in the weft only a trace of alizarin wasfound. It is impossible to say with certainty that the weft was dyed.Rather, it is likely that it was undyed or only slightly colouredcompared to the warp. No dyes were found in the threads of tablet-woven borders. The analysed red tassel however, contained bothalizarin and purpurin, with a relative peak area ratio at 255 nm of90 alizarin over 10 purpurin.

In the Tegle textiles, alizarin was detected twice together withindigotin in the warp fringe (sample 190) and the warp from the 2/2twill textile (sample 192) respectively, while alizarin and a trace ofpurpurin were found in the weft fringe thread from Tegle (sample 191).

The presence of alizarin as the principal anthraquinone found,rather suggests the use of a madder-like type of dye instead of the

more local Galium or Asperula species, which have purpurin as themajor characteristic component (Cardon, 2007).

4.2.4. Other constituentsCharacteristic to the chromatograms of all archaeological

samples of this corpus is the presence of the many small peaks,having no absorbance in the wavelengths of the visible light. A lot ofthem are derivates of cinnamic and benzoic acid. They could refer todegradation products of dyes (Ferreira et al., 2003; Peggy, 2006),fibres or either be related to skins or human remains buried in closecontact with the textile finds. Furthermore, considering that mostof the finds were excavated in the 19th and early 20th century, norecords on their conservation exist, making it possible that thesesubstances may refer to the conservation agents.

Apart from the identified components, five characteristicconstituents were signalised. Four of them have their maximumabsorption around the range of 400–500 nm, hence suggestingreddish colouring matters. The UV-Visible absorbance spectra andretention times of the five constituents are given in Fig. 3. Three ofthem could not be identified, while unknown 1 showed highcorrelation with the spectral data from the laboratory reference ofyellow wall lichen (Xanthoria parietina L.). For unknown 3, highsimilarity is found with Scandinavian orchil, with alkannet and withanthocyanidin glycosides, however the latter falling much earlier inthe chromatogram. Based on both the analytical aspect and on thehistorical context of the samples, Scandinavian orchil (Ochrolechiatartarea L.) would be the most probable source. A probable lichenpurple was detected in one of the 3rd–4thcentury AD textiles fromSlusegård, Denmark (Walton Rogers, 1995, 137; Fig. 2).

4.2.5. Ellagic acidThe detection of ellagic acid by chromatographic analysis is

indicative for the presence of tannin material. Tannin containingplants could have been deliberately used for the conversion ofanimal skins into leather, or as a mordant or dye in the textiledyeing process (Hofenk de Graaff, 2004). On the other hand, onecannot exclude the influence of the peat bog environment, beingrich of tannin material. In fact the preservative qualities of the bogenvironment have been shown to be largely due to the conversionof the polysaccharide sphagnan, produced by the Sphagnum moss,into the humic acid, which triggers complex chemical reactionsleading to the tanning of the skins and bodies in the bog (Painter,1995, 1998).

However, the finding of ellagic acid not systematically, but onlysix times, in samples belonging to different textiles and to differentsites of excavation, rather suggests that tannin was applied to theyarn or textile as mordant together with organic dyes, or as the dyeconstituent itself. Black dyeing with tannin in the presence of iron isa well-known ancient technique (Cardon, 2007, 42–46), but alsoother colours can be obtained with the use of tannin alone forinstance to achieve yellow shades (Golikov and Vishnevskaya,1990). The detection of ellagic acid, three times together with bothluteolin and indigotin, once in combination with luteolin, oncealone and one time together with indigotin, rather refers to its useas a mordant. As in the two last cases no indication was found ofa mordant dye, it is most likely that this dye did not survive theburial conditions. Similar situation was reported previously forseveral Norwegian and Danish finds (Walton, 1988).

5. Discussion

5.1. Abundance of yellow – luteolin containing dye source

Traces of luteolin were found in almost all textiles except thethree textiles where no dye components were found at all, and the

Unknown 1 (415) Unknown 2 (422) Unknown 3 (503)

Unknown 4 (414) Unknown 5 (324)

218

262

397- 414

Rt 20.3

286

324

Rt 17.8

257

295

415

Rt 19.3 259

287

334

422Rt 21.6

223

279

503

Rt 22.3

Fig. 3. UV-Visible absorbance spectra and retention time (Rt) of unidentified dye constituents.

Vanden Berghe, T. et al. / Journal of Archaeological Science 36 (2009) 1910–1921 1919

textiles from Søgårds Mose II and Skærsø, which contained indi-gotin and alizarin respectively. This is the first series of archaeo-logical samples where a flavonoid dye was found so frequently.

The fact that traces of luteolin are so abundantly present in thiscollection brings up the question whether we can conclude that allthese textiles were dyed with a yellow dye source, or if the flavo-noid components are present in the textiles as a result of possibleeffect of the bog environment. The following arguments can begiven in favour of the first interpretation.

First, the bogs from which the finds originate include a verylimited repertoire of plant species, consisting mostly of variousmoss species of Sphagnum (van der Sanden, 1996, 22), none ofwhich naturally contain luteolin. The analysis of peat bog samplestaken recently at a bog near Silkeborg in East Jutland, Denmark,following the same procedure as used for the textiles, did not revealany traces of luteolin. Second, apart from luteolin alone, also tracesof luteolin together with other flavonoid dye components such asapigenin and quercetin were found. The detection of rhamnetinprovides further evidence that flavonoid dyes, other than luteolincontaining ones, can survive peat bog conditions. Finally, luteolin isnot present in two textiles where other dyes were used, the Skærsøfind containing the red dye source from the Rubiaceae family andthe woad dyed Søgårds Mose II find. Based on the present study ofthe natural organic dyestuffs in this large Early Iron Age corpus, thearguments presented above rather support the hypothesis of theapplication of a yellow dye source.

For all the textiles that do contain luteolin, it is quite remarkablethat it has been used often in combination with woad dyeing for thecreation of stripes and checked patterns by the use of differentcoloured warps and wefts. This is also the case in other European

finds, for example the textiles found in the salt-mines of Hallstatt,Austria, dating 800–400 BC (Hofmann-de Keijzer et al., 2005),where luteolin and apigenin, as well as other flavonoids have beenidentified often in combination with indigotin and other dyestuffs.

A combination of an unidentified yellow with indigotin wasreported for the Late Roman/Migration period textiles from Blind-heim, Veiem and Sætrang in Norway and Rovsbjerghøj in Denmark(Bender Jørgensen and Walton, 1986; Walton, 1988). Luteolin wasalso detected in the Gerum cloak, a bog find from Sweden dated360–100 BC (Franzen et al., forthcoming).

5.2. Towards dye technology in Early Iron Age

The detection of dye constituents in the majority of the samples,despite only being present at trace levels, clearly indicates that mosttextiles originally were coloured using plant dyes. Only in thetextiles from Stidsholt and an unknown site both dated between400 and 200 BC, no evidence of the use of biological dye sources wasfound. This however does not indicate that they were not dyedoriginally, only that the dyes that may have been present did notsurvive over time or are either not detectable by HPLC. A small testof two sets of samples from the same textiles from Grathe Hede(samples 158/182, 159/183 and 160/184) and from Haraldskær(samples 23/125, 12/17, 13/15/19, 14/18 and 16/20) also showed thatdye components are sometimes not detected anymore, most prob-ably due to the heterogeneity of the dyes remaining on the textiles.

The application of the woad plant for dyeing purposes was rec-ognised in textile finds from ten Scandinavian bog finds chrono-logically distributed throughout the Early Iron Age. The oldestindigotin dyed find is from Rebild, dated between the 4th and the

Vanden Berghe, T. et al. / Journal of Archaeological Science 36 (2009) 1910–19211920

3rd century BC. It provides evidence for the earliest use of indigotinin Scandinavia. Until now, indigotin has been identified in fivetextiles from Lønne Hede, one textile from Donbæk two textilesfrom Hjørring Præstegårdsmark, one textile from Tornebuskehøjand one textile from Rovsbjerghøj, all Roman Iron Age (AD 1–400)burial sites in Denmark, as well as several Late Roman/Migration/Viking Age (AD 300–1050) textiles from burials in Norway (BenderJørgensen and Walton, 1986; Walton, 1988). Our findings thusindicate that the use of woad in Scandinavia can be extended severalcenturies back in time. In central and southern Europe, however, theuse of woad goes back to even earlier times. Thus, indigotin has beenidentified in the textiles found in the salt-mines of Hallstatt, Austria,dating 800–400 BC (Hofmann-de Keijzer et al., 2005), in the 8thcentury BC garments from the princely burials in Verucchio, Italy(Vanden Berghe, 2002) and in the 6th century BC princely burial inHochdorf, Germany (Walton Rogers, 1999). Recently, indigotin hasbeen identified in the textiles from Hallstatt dated to the MiddleBronze Age (1600–1200 BC), making this the earliest instance ofwoad use in Europe (Hofmann-de Keijzer et al., 2007).

The first instance of the use of a madder-like dye in the analysedcollection is detected in the Skærsø textile, dated to the 1st centuryBC. Madder was not cultivated in Scandinavia during Early Iron Age,suggesting that the dye or the dyed textile may have been tradedlong distance (Walton, 1988). Irrespective of its origin, the Skærsøtextile provides the earliest evidence of madder use in Scandinavia.Madder was also found in Late Roman period textiles from Rovsb-jerghøj and Slusegård in Denmark (Walton, 1988; Walton Rogers,1995) and Late Roman/Migration period textiles from Tofte, Veiem,Snartemo V and Evebø/Eide in Norway (Bender Jørgensen andWalton, 1986; Walton, 1988), which corresponds well to our resultsfor the textiles from Tegle, Norway. A red dye source from theRubiaceae family was also found in two Danish grave finds (Taylor,1992) and in a tablet-woven band from a tunic found in the grave-mound at Hogom in Sweden (Hofenk de Graaff, 2004), all from theMigration Period (AD 400–520/540). In these fragments however,purpurin was identified without alizarin, hence suggesting anotherRubiaceae species. The Scandinavian finds thus indicate thatmadder became a more common dye source in Scandinavia onlyduring the Migration period.

Unlike in the case of finds from Hallstatt, Austria (Hofmann-deKeijzer et al., 2005) and Hochdorf, Germany (Walton Rogers, 1999),no insect dyes have been identified among the Scandinaviantextiles. This, however, is not surprising, since the presence of thesedyes among the Central European finds is interpreted as a result oflong distance exchange with the Mediterranean areas.

6. Conclusions

Evaluation of different dye extraction and HPLC techniquesmade it possible to select the most appropriate analytical protocolfor the archaeological bog samples. The method using acidifiedmethanol extraction followed by a second extraction in ethylacetate extraction was applied for the complete series of peat bogtextiles.

Natural organic dyes found in the Scandinavian textiles repre-sent the three main categories of natural dyes hence throwing newlight on the use of biological dye sources in Early Iron Age Scan-dinavia. Among the detected dye constituents are flavonoid dyecomponents luteolin, apigenin, quercetin and rhamnetin, indigoiddyes indigotin and indirubin as well as the anthraquinone dyesalizarin and purpurin. Interesting comparison was also found withlichen dyes, calling for further study focused on specific local lichendye sources and other local sources. Taken into account that onlytraces of dye components were detected, it has to be consideredthat dyes might have been missed.

The results indicate that the vast majority of the ScandinavianEarly Iron Age textiles recovered from peat bogs originally weredyed. Already during the Pre-Roman Iron Age (500–1 BC), thepopulations in Scandinavia were familiar with the dyeingtechnology.

As far as the dyeing technology is concerned, our opinion is thatmost fabrics were dyed as finished pieces. The complete staining ofthe textiles in the bog does not provide any visual evidence as to thedyeing technique. However, in many cases, all threads from thetextiles that are patterned using naturally pigmented wool, testedpositive for the same dyestuffs. Thus, all four samples (two from thewarp and two from the weft) from the Huldremose I skirt, woven ina checked pattern, contained indigotin, luteolin and unknown 5.This furthermore indicates that multiple stage dyeing was per-formed, demonstrating the familiarity of the Early Iron Age Scan-dinavians with the dyeing technology and their ability to combinedifferent dyes. Piece dyeing is an ancient technique, which has beendefinitively demonstrated to be the method for the Middle BronzeAge textiles from Hallstatt, Austria, the earliest European textiles, inwhich dyes have been detected (Hofmann-de Keijzer et al., 2007).

Some cases indicate that at least occasionally, yarn was dyed inorder to create patterned textiles. In the Bredmose scarf, the reddishyarn, creating a grid check pattern tested positive for indigotin,while the rest of the textile contained luteolin. Sometimes, bothtechniques were combined, as in Krogens Mølle Mose skirt, whichhad three blue stripes woven into the background and then theentire piece was coloured with a luteolin-containing dyestuff.

The dyestuffs found in Early Iron Age Danish and Norwegian bogtextiles fit well into the repertoire of dyes used throughoutNorthern and Central Europe during the Iron Age. While it isprobable that the dyestuffs were not derived from the same plantspecies throughout Europe, many of the sources were similar.Woad, in particular, is the most likely source for blue colour all overEurope. Further work is necessary to identify plant sources withmore precision but there can be little doubt that already during the1st millennium BC there existed a well-developed pan-Europeandyeing technology.

Acknowledgements

The authors would like to thank Jenny Dean, Su Grierson and Dr.Helmut Schweppe for the references offered to the laboratory andDr. Beatrice Devia and Marie-Christine Maquoi for the collaborationin the lab. Sunniva Halvorsen from the University of Bergen and ÅsaD. Hauken at the Stavanger Museum were instrumental in obtain-ing the Norwegian samples. We also would like to thank thefollowing colleagues at the Danish museums: Irene Skals, NationalMuseum of Denmark, Copenhagen; Steen Wulff Andersen, VejleMuseum, Vejle; Broder Berg, Vesthimmerlands Museum, Års;Christian Fischer, Silkeborg Museum, Silkeborg; Per Thorling Had-sund, Nordjyllands Historiske Museum, Ålborg; Margit Petersen,Viborg Stiftsmuseum, Viborg; John Simonsen, Skive Museum.Museet for Salling og Fjends, Skive; Ernst Stidsing, KulturhistoriskMuseum Randers, Randers.

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