Analysis of synthetic dyes in an embroidery of Emile Bernard (circa 1892)
M R van Bommel* and A M Wallert
Netherlands Institute for Cultural Heritage
PO Box 76709
1070 KA
Amsterdam
The Netherlands
E-mail: Maarten.van.Bommel@icn.nl
Web site: www.icn.nl
I Vanden Berghe and J Wouters
Royal Institute for Cultural Heritage
Jubelpark 1
B-1000 Brussels
Belgium
E-mail: Ina.vandenberghe@kikirpa.be; Jan.Wouters@kikirpa.be
Web site: http://www.kikirpa.be
J Barnett
Regina Textilia
Historical textiles research and consultancy
Oude Looierstraat 65-67
1016 VH
Amsterdam
The Netherlands
E-mail: reginatextilia@ision.nl
R Boitelle
Van Gogh Museum
PO Box 75366
1070 AJ
Amsterdam
The Netherlands
E-mail: boitelle@vangoghmuseum.nl
Web site: www.vangoghmuseum.nl.
*Author to whom correspondence should be addressed
Abstract
Research focused on early synthetic dyes is presented. A selection of 65 dyestuffs, produced in
the period 1850–1900, had been investigated previously. Both non-destructive and destructive
analytical techniques were evaluated for dyestuff identification. To establish the effectiveness of
the selected dyes and the suitability of the analytical techniques, well-dated objects have to be
examined. Therefore, an embroidery designed by Emile Bernard (dated 1892) was studied; the
results are presented in this paper. In 27 samples taken from the object, 13 different synthetic
dyes and 3 natural dyes were detected, often in mixtures. Only two dyes could not be identified.
The blue, mauve, purple and green colours were all severely faded whereas the red, pink and
yellow colours turned out to be more stable.
Keywords
synthetic dyes, high-performance liquid chromatography, 3D fluorescence, embroidery, Emile
Bernard
Introduction
Since the introduction of modern analytical techniques, progressively more attention has been
paid to the analysis of natural dyes of historical or art objects. In contrast, the analysis of
synthetic dyestuffs is a somewhat unexplored area. Since the invention of mauve by W H Perkin,
in 1856, natural dyestuffs have been rapidly replaced by synthetics. By 1900, approximately 400
new dyestuffs had been developed (Lehne 1893) although they were not all produced
commercially. Recently a selection of 65 synthetic dyes covering all dye classes available in the
period 1850–1900 was investigated (Van Bommel 2004). For analysis, threedimensional (3D)fluorescence spectrometry with a fibre optic system was used in a first phase. This nondestructive technique, showing the interaction between emission wavelength, excitation
wavelength and emission intensity, can be used for natural and synthetic dye identification.
Subsequently, high-performance liquid chromatography (HPLC) was used in combination with
photo diode array detection (PDA). With PDA detection, ultraviolet-visual (UV-vis) absorption
spectra from 200 to 700 nm were measured from all the components separated with HPLC. The
combination of these spectra and their chromatographic behaviour is a powerful tool for
identification of dyestuffs. Two different HPLC procedures were evaluated. First, the HPLC
procedure developed by Wouters (1992), using a gradient of water, methanol and phosphoric
acid, for the identification of natural dyestuffs was applied to synthetic dyes. Most synthetic
dyestuffs can be analysed using this system and the basic dyes in particular show excellent
results. On the contrary, the results of the acid dyes were less satisfying because of the bad
chromatographic properties under these conditions. Therefore, a second HPLC procedure was
tested using a gradient of water, methanol and tetrabutyl ammonium hydroxide (TBA). TBA acts
as counter ion to the negatively charged acid dyes, resulting in improved chromatographic
behaviour and in a significant improvement of detection limits. Some of the selected dyestuffs
were identified on numerous objects (Whiting 1978, Rabe et al. 1990, Wouters 1992) but it is
unknown if the selection covers all the important synthetic dyestuffs used in the second half of
the 19th century. To gain more knowledge of these dyestuffs and to demonstrate the suitability of
the techniques, accurately dated objects need to be analysed. The present research focuses on
embroideries designed by Emile Bernard. Five of these embroideries, part of the Bonger
Collection, are now kept at the Vincent van Gogh Museum, Amsterdam, The Netherlands. As
part of the Preservation of Cultural Patrimony Act, in 1996 the Dutch State acquired the
collection of Andries Bonger, which is administered by the Van Gogh Museum. Andries Bonger
(1861–1934) was a merchant who lived in Paris from 1879 where he struck up a friendship with
Theo van Gogh, Vincent van Gogh’s brother. Theo introduced Bonger to the work of French
avant-garde artists. After returning to The Netherlands in 1892, Bonger began collecting art
himself, in particular the works of two friends, Odilon Redon (1840–1916) and Emile Bernard
(1868–1941).
The first embroidery selected for examination is Bernard’s Two Breton Women, circa 1892; wool
on cotton, trimmed with a braided border and stretched on a strainer (78 cm × 61 cm). The work
(Figures 1 and 2) is now extremely faded and is dominated by a greenish grey hue, whereas the
unexposed parts of the textile still show a wide range of very bright colours. Owing to its date
and the extreme fading, early synthetic dyes were expected to be present. Because long yarn end
are present at the back of the object, samples for dyestuff analysis could be easily taken without
disturbing the integrity of the object. The experimental details of the techniques are described in a
subsequent paper (Van Bommel et al. 2005).
Results and discussion
Red and pink yarns
The results of the analysis of the red and pink yarns are presented in Table 1. The red yarns were
dyed with synthetic colourants: cochineal red A (CI-16255)1, ponceau RR (CI-16150) and
ponceau 3RO (CI-16050). Ponceau 3RO is present in a small amount. These colourants belong to
the class of acid red dyestuffs. The ratio of the mixture of the three dyes in samples 1 and 2,
determined with HPLC, indicates a small difference in concentration: the concentration of
cochineal red A in sample 2 was about 10 per cent higher. There is no colour difference visible at
the back of the object and, as the samples were taken from the red dress, colour differences were
not expected. However, on the front of the object, which has been exposed to light (Figure 3),
sample 2 is faded to a more orange colour whereas the other part is still red. Although analysis of
samples from the front of the object was impossible, one can still conclude that cochineal red A is
less light-fast compared with the other dyestuffs in this area. Sample 3 consists only of ponceau
RR, which means that a different dye was used. This area shows yet another red colour compared
with the area where sample 1 and 2 were taken. A small amount of naphthol yellow S was found
as well, but this could be a cross-contamination; that is, some fibres from another location could
have contaminated the sample. The pink samples were dyed with carminic acid (CI-75470) in a
rather low concentration, which explains the pink colour. Carminic acid indicates the use of a red
insect dye from a natural origin. Considering the date of the object, cochineal (Dactylopius
coccus L) is most likely as synthetic carminic acid was not developed until 1991 (Pietro 1998).
Cochineal can be more precisely identified by means of minor components. However, because of
the low concentration, no
Figure 1. Front of embroidery Two Breton Women, designed by Emile Bernard, circa 1892
Figure 2. Back of embroidery Two Breton Women, designed by Emile Bernard, circa 1892
Table 1. Analytical results of the red and pink yarns
Figure 3. Detail of discolouration of the red dress of the woman on the left. The number on the
white arrows corresponds with the sample number in Table 1. The samples are taken from the
back
minor components were found in samples 4 and 6. In sample 5, minor components were found,
among them dcII, which proved that cochineal was used (Wouters and Verhecken 1989). The
pink colours were slightly faded whereas the fading of the red areas dyed with synthetic dyes was
much stronger. 3D fluorescence made it possible to recognize the presence of a combination of
several acid red colourants on the red samples and to detect the presence of cochineal on both
pink samples. Although the acid dyes were readily identified with the use of the TBA gradient,
the results of the phosphoric acid were less easy to interpret owing to the bad chromatographic
properties under the conditions used. Carminic acid, a natural dye, was identified with phosphoric
acid gradient. Some acid red dyes together with carminic acid were found in sample 4 with the
use of the phosphoric acid gradient. Because these red acid dyes were not found in this sample
with the TBA gradient, it is believed that this is caused by sample carry-over from the previous
analysis.
Yellow and green yarns
Both synthetic and natural dyes were found in the yellow and green samples (Table 2). In sample
7, naphthol yellow S (CI-10316), Martius yellow (CI- 10315) and picric acid (CI-10305) was
found. Because the concentration of Martius yellow and picric acid was very low, these are
considered to be byproducts. Sample 8 was dyed with the yellow picric acid, which was
originally derived from blue indigo (Indigofera tinctoria L) by the treatment of concentrated
nitric acid (Christie 2001). After 1841, a procedure was developed to produce picric acid from
phenol. In sample 9, both synthetic and natural dyestuffs were found. Naphthol yellow S and
picric acid were found in an approximately equal ratio. The identification of quercetin, kampferol
and rhamnetin indicates the use of the natural dye buckthorn or Persian berries (Rhamnus
species). However, the presence of buckthorn was not confirmed by 3D fluorescence
spectrometry, where auramine (CI-41000) was clearly identified as main dye. The different
analytical results cannot be explained, a larger sample has to be analysed as the concentration
dyestuffs found with HPLC was rather low. A mixture of natural and synthetic dyes was also
found in sample 10 where picric acid, luteolin and apigenin, indicating the use of weld (Reseda
luteola L) were found. In this sample, picric acid was present in abundance. The combination of
natural and synthetic dyes is unexpected, since these are mordant and acid dyes respectively.
Using two different dyeing procedures makes the preparation of the textiles complicated. The
fading of these yellow areas is not severe. The pale colours (samples 9 and 10) look more faded
than the bright yellow in samples 7 and 8. The two green samples were both dyed with a mixture
of indigo carmine (CI- 73015) and picric acid. Indigo carmine is prepared by treating indigo with
concentrated sulphuric acid; as a result, mono-sulphonic and di-sulphonic indigotin are formed
(Christie 2001). Mixing the blue and yellow dye resulted in the green colour observed. Dyeing
green by mixing yellow and blue dyestuffs was not uncommon. As there are no stable green
natural dyes, dyeing green has been done with yellow and blue dyes for centuries. When
synthetic dyestuffs were developed, one was able to dye green with a single dye, but the result of
Table 2. Analytical results of the yellow and green yarns
The two green samples were both dyed with a mixture of indigo carmine (CI- 73015) and picric
acid. Indigo carmine is prepared by treating indigo with concentrated sulphuric acid; as a result,
mono-sulphonic and di-sulphonic indigotin are formed (Christie 2001). Mixing the blue and
yellow dye resulted in the green colour observed. Dyeing green by mixing yellow and blue
dyestuffs was not uncommon. As there are no stable green natural dyes, dyeing green has been
done with yellow and blue dyes for centuries. When synthetic dyestuffs were developed, one was
able to dye green with a single dye, but the result of these samples indicates that mixing dyes was
done as well. The ratio between the two dyes in both samples is approximately 10 per cent indigo
carmine and 80 per cent picric acid. However, the concentration of dyestuffs found in the dark
green sample 12 was about nine times that in green sample 13, which seems to be much more
faded on the front of the object. With the exception of sample 9, analytical results of the
techniques applied were consistent. Out of the 3D contour plot from the yellow samples 7 and 8,
a yellow colourant from the type of picric acid, Martius yellow and/or naphthol yellow S was
detected and in the green samples indigo carmine as well. However, with this technique no
distinction can be made between these synthetic yellow dyes. It is not always possible to
differentiate even indigo carmine from them as they all are emitting in the same area. Not only
interference between the colourants but also of the yarns itself emits in that part of the contour
plot. Hence, HPLC needs to be applied for more definite interpretation of the 3D fluorescence
results.
Blue and turquoise textiles
All blue and turquoise textiles were dyed with synthetic dyes (Table 3). Sample 11 was divided
into two separate samples because the textile fibres themselves had differing textures. However,
both samples were dyed with indigo carmine: two indigo carmine components were found. As
indigo carmine is an acid dye, the response with the phosphoric acid gradient is very low. The
ratio between these two components differs in these samples, which could indicate the use of a
different dye bath. Furthermore, a small amount of an unknown red component was found in both
samples. This colourant has a spectrum comparable with that of indirubin, a stereoisomer of
indigotin (Schweppe 1992). Therefore, this component could be sulphonated indirubin, but
positive identification is not possible due to the lack of reference material. The presence of an
unknown red colourant in the presence of indigo carmine is often also recognizable on the 3D
contour plot. Indigo carmine was also identified in four of the six blue samples. However, in
these samples other blue or violet components were also found such as fuchsine (CI-42510) and
methyl violet (CI-42535). These dyes belong to the basic violet dyes and are mixtures of
triphenyl methanes, that is, three phenyl groups attached to one central carbon atom. Generally,
basic dyes gave better results with the phosphoric acid gradient. The phenyl groups can have
different side groups. Fuchsine consists of four components that are well separated with slightly
different spectra. Methyl violet is a mixture of tetra-, penta- and hexamethylated pararosaniline.
The hexa-methylated form is also known as crystal violet (CI-42555). See Figure 4 for the
chromatogram of sample 14. In addition to the four fuchsine components, the three methyl violet
components were detected. The combination of the three components indicates the use of methyl
violet. The ratio between the blue indigo carmine and the violet fuchsine and methyl violet
cannot be calculated at the moment because they were identified with different HPLC systems.
Quantification can be done with the use of accurately weighted standards of the colourant, but
this is beyond the scope of this paper. The constitution of the dyestuffs in sample 15.1 was very
complex. Besides indigo carmine, fuchsine and methyl violet, numerous colourants were found
with spectra similar to fuchsine and methyl violet but eluting at different retention times. This
means that these components are closely related and could be by-products. These components
were not found in the other samples. Since the amount of sample and dye is approximately the
same in all blue samples, these by-products indicate another dye bath. Diamond green G (CI42040) and diamond green B (CI-42000) were found as well. The concentration of the green
components was much higher than the concentration of fuchsine and methyl violet. The ratio
between indigo carmine and diamond green cannot be calculated as the analytical procedure for
both dyes is different. From the same area, a second sample was taken which was faded even at
the back of the object. Sample 15.2 was dyed with a mixture of indigo carmine and diamond
green G and B. Basic violets, such as fuchsine and methyl violet were not present, it could be that
these were completely faded. The fourth blue sample where indigo carmine was found, sample
17, was dyed with colourants with spectra similar as methyl violet. However, methyl violet was
not found in this sample. These colourants remain unidentified but belong to the class of basic
violets. Two blue samples, 16 and 18, were dyed with water blue IN (CI-42780). Despite the fact
that this is an acid dye, the result obtained with the phosphoric acid gradient was significantly
improved compared with the result of the analysis with TBA gradient because this dyestuff
contains basic groups as well. The colour difference can be explained by the concentration of the
dyestuff present. In sample 16, the concentration dyestuff was about eight times higher than in
sample 18, which was pale blue.
Table 3. Analytical results of the turquoise and blue yarns
Figure 4. HPLC chromatogram of sample 14. The dye consists of a mixture of four components,
indicating fuchsine and three components that point to the use of methyl violet
Figure 5. Detail of discolouration of the blue area of the tree between the two women. A sample
taken from the back is shown with the area at the front to illustrate the discolouration
With 3D-fluorescence, indigo carmine was detected on both turquoise samples (11.1 and 11.2),
while the blue samples 14, 16, 17 and 18 showed an identical contour plot from which Water blue
IN could clearly be identified. On blue samples 15.1 and 15.2, a combination of Diamond green
B or G and indigo carmine were detected. Taking into account that the identification of indigo
carmine is impossible in the presence of Water blue IN because of interference of the last one,
and that minor colourants risk being undetectable in the 3D-contour plot, these results are very
close to what is found with the chromatographic techniques with the exception of samples 14 and
17. In sample 14, indigo carmine, fuchsine and methyl violet were identified with HPLC, and in
sample 17 indigo carmine and an unknown basic violet, but clearly not water blue IN. This
inconsistency could be because dyes were mixed with closely related spectra. All the turquoise
and blue samples were seriously faded to a greyish-green colour (Figure 5). The area where
sample 15 was taken was a little bit more greenish compared with other areas, presumably
because of the presence of diamond green.
Miscellaneous coloured yarns
The results of the mauve, purple, brown and cream samples are presented in Table 4. The two
mauve samples were dyed with fuchsine; the colour difference observed is caused by the fact that
the darker mauve contains a double concentration of fuchsine. Fuchsine was also found in the
purple sample, together with methyl violet. Both purple and mauve areas were seriously faded.
As the purple area was more faded than the two mauve areas, one can conclude that methyl violet
is less light-fast. In the brown and light brown yarns, samples 22 and 23 respectively, picric acid
and indigo carmine were found. The amount of indigo carmine in relation to the amount of picric
acid in these samples is approximately twice as low as in the green samples 12 and 13. For that
reason, the picric acid predominates, resulting in the colours observed. Furthermore, the
concentration of dyestuff in the brown sample was higher then in the light brown sample,
resulting in a darker colour. Finally, two samples were analysed which were almost colourless.
Dyestuffs were found, but at a very low concentration. As a result, it was not possible to identify
the red dyestuff found in sample 25, but it is different from sample 24, where cochineal was
found. The red dyestuff in sample 25 is most likely of anthraquinone type dye; whether it has a
natural or a synthetic origin remains unknown. The 3D-fluorescence analysis revealed the same
main synthetic dyes as discussed above, except for the almost completely faded samples 24 and
25 where it was no longer possible to detect any colourant.
Conclusion
3D fluorescence spectrometry has proved to be very useful as a first scanning technique for
synthetic dye identification before destructive techniques are applied. However, as the
interpretation of a 3D contour plot is not always reliable because of interference between the
colourants and the wool fibre, and as minor colourants risk staying undetected, it should be
applied complementary to chromatographic techniques. The use of the phosphoric acid gradient
showed excellent results for natural and basic dyes, whereas the acid dyes showed much better
results with the TBA gradient. As many different dyes were found, the combination of both
HPLC techniques and 3D fluorescence spectrometry is preferred when sample size allows. Most
yarns were dyed with synthetic dyes, although some natural dyes were found as well. The colours
observed are consistent with the dyes found. Mixtures and variations in concentration were
applied to achieve a specific colour or shade. It is interesting that different dyeing processes, such
as acid, basic and mordant dyeing were used on a single yarn to obtain the final colour. The
embroidery is severely faded and particularly the balance between the different colours is lost
since dark colours, such as blue, purple and green are much more faded then the yellow, pink and
red colours. Generally, the fading is stronger when the concentration dyestuff is lower. Based on
the results of this examination, it can be concluded that the original appearance was very different
from its present one.
Notes
1 Colour index (CI) numbers of the synthetic dyes identified are derived from the
Colour Index 1971, 3rd edition, Society of Dyers and Colourists, Bradford, England.
Table 4. Analytical results of the miscellaneous coloured yarns
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