Data from: Investigation of ph-dependent wash fastness of indigo carmine in replica and historical textile fibers
Data files
Jul 06, 2026 version files 356.64 KB
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Few-fiber_pH5_pH8.5_microextraction_UVVis_raw-data.csv
40.28 KB
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Historical-textiles_pH5_pH8.5_microextraction_UVVis_raw-data.csv
27.53 KB
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README.md
21.94 KB
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Washfastness-IndigoCarmine_pH4-pH5_pH7_pH8.5_UVVis_raw-data.csv
158.31 KB
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Washfastness-Madder-Indigo_pH4-pH5_pH7_pH8.5_UVVis_raw-data.csv
108.59 KB
Abstract
Indigo carmine is a semi-synthetic blue dye encountered in historical textiles which poses conservation challenges due to its poor wash fastness and tendency to transfer during aqueous treatments. Textile fibers dyed with indigo carmine often exhibit color migration during conservation wet cleaning, complicating preservation efforts. Due to the nature of indigo carmine interactions with proteinaceous textile fibers, this study assessed whether the pH-dependence of the wash fastness of indigo carmine combined with absorbance spectroscopy could be utilized as a simple identification technique. First, the pH-dependent wash fastness of wool samples dyed with indigo carmine was assessed and compared to samples dyed with natural indigo and madder as a negative control. UV-Visible absorbance data collected from wash fastness tests conducted using water adjusted to pH 4, 5, 7, and 8.5 revealed strong pH dependence for only indigo carmine, with minimal dye migration at acidic pH, some dye migration at neutral pH, and the highest degree of dye migration occurring at pH 8.5. Negative controls samples of wool dyed with indigo and madder show no dye migration, indicated by no UV-Vis absorbance peaks present in the wash solution spectra. We optimize a pH-dependent microextraction test for few-fiber samples using sub-milliliter wash volumes, successfully identifying indigo carmine in both replica and historical samples, using UV-Visible absorbance spectroscopy. Finally, we demonstrate the positive identification of indigo carmine in select historical samples using the UV-Vis absorbance pH-dependent microextraction test. Overall, these findings contribute to the understanding of indigo carmine’s behavior and provide guidance for historical dye identification and decision making in textile conservation treatments.
Dataset DOI: 10.5061/dryad.qfttdz0w
Files and variables
File: Washfastness-IndigoCarmine_pH4-pH5_pH7_pH8.5_UVVis_raw-data.csv
Description: UV-Visible absorbance spectral data for pH-dependent wash fastness data for wool samples dyed with indigo carmine. Three samples were prepared (pretreatment of wool prior to dyeing: no treatment, sodium sulfate treatment, alum and cream of tartar treatment). The washfastness of each sample was tested by washing the sample a total of four successive times. This process was done using water adjusted to four different pH values: 4, 5, 7, and 8.5.
Variables:
- Wavelength(nm): Wavelength in nanometers at which absorbance data in following rows was collected.
- pH 4 IC-no-pretreatment_wash1(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 4. First successive wash of four.
- pH 4 IC-no-pretreatment_wash2(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 4. Second successive wash of four.
- pH 4 IC-no-pretreatment_wash3(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 4. Third successive wash of four.
- pH 4 IC-no-pretreatment_wash4(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 4. Fourth successive wash of four.
- pH 5 IC-no-pretreatment_wash1(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 5. First successive wash of four.
- pH 5 IC-no-pretreatment_wash2(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 5. Second successive wash of four.
- pH 5 IC-no-pretreatment_wash3(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 5. Third successive wash of four.
- pH 5 IC-no-pretreatment_wash4(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 5. Fourth successive wash of four.
- pH 7 IC-no-pretreatment_wash1(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 7. First successive wash of four.
- pH 7 IC-no-pretreatment_wash2(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 7. Second successive wash of four.
- pH 7 IC-no-pretreatment_wash3(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 7. Third successive wash of four.
- pH 7 IC-no-pretreatment_wash4(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 7. Fourth successive wash of four.
- pH 8.5 IC-no-pretreatment_wash1(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 8.5. First successive wash of four.
- pH 8.5 IC-no-pretreatment_wash2(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 8.5. Second successive wash of four.
- pH 8.5 IC-no-pretreatment_wash3(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 8.5. Third successive wash of four.
- pH 8.5 IC-no-pretreatment_wash4(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 7. Fourth successive wash of four.
- pH 4 IC-Na2SO4_wash1(Abs): Absorbance data of wool (pre-treated with a sodium sulfate solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 4. First successive wash of four.
- pH 4 IC-Na2SO4_wash2(Abs): Absorbance data of wool (pre-treated with a sodium sulfate solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 4. Second successive wash of four.
- pH 4 IC-Na2SO4_wash3(Abs): Absorbance data of wool (pre-treated with a sodium sulfate solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 4. Third successive wash of four.
- pH 4 IC-Na2SO4_wash4(Abs): Absorbance data of wool (pre-treated with a sodium sulfate solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 4. Fourth successive wash of four.
- pH 5 IC-Na2SO4_wash1(Abs): Absorbance data of wool (pre-treated with a sodium sulfate solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 5. First successive wash of four.
- pH 5 IC-Na2SO4_wash2(Abs): Absorbance data of wool (pre-treated with a sodium sulfate solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 5. Second successive wash of four.
- pH 5 IC-Na2SO4_wash3(Abs): Absorbance data of wool (pre-treated with a sodium sulfate solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 5. Third successive wash of four.
- pH 5 IC-Na2SO4_wash4(Abs): Absorbance data of wool (pre-treated with a sodium sulfate solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 5. Fourth successive wash of four.
- pH 7 IC-Na2SO4_wash1(Abs): Absorbance data of wool (pre-treated with a sodium sulfate solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 7. First successive wash of four.
- pH 7 IC-Na2SO4_wash2(Abs): Absorbance data of wool (pre-treated with a sodium sulfate solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 7. Second successive wash of four.
- pH 7 IC-Na2SO4_wash3(Abs): Absorbance data of wool (pre-treated with a sodium sulfate solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 7. Third successive wash of four.
- pH 7 IC-Na2SO4_wash4(Abs): Absorbance data of wool (pre-treated with a sodium sulfate solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 7. Fourth successive wash of four.
- pH 8.5 IC-Na2SO4_wash1(Abs): Absorbance data of wool (pre-treated with a sodium sulfate solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 8.5. First successive wash of four.
- pH 8.5 IC-Na2SO4_wash2(Abs): Absorbance data of wool (pre-treated with a sodium sulfate solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 8.5. Second successive wash of four.
- pH 8.5 IC-Na2SO4_wash3(Abs): Absorbance data of wool (pre-treated with a sodium sulfate solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 8.5. Third successive wash of four.
- pH 8.5 IC-Na2SO4_wash4(Abs): Absorbance data of wool (pre-treated with a sodium sulfate solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 8.5. Fourth successive wash of four.
- pH 4 IC-alum+CC_wash1(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 4. First successive wash of four.
- pH 4 IC-alum+CC_wash2(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 4. Second successive wash of four.
- pH 4 IC-alum+CC_wash3(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 4. Third successive wash of four.
- pH 4 IC-alum+CC_wash4(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 4. Fourth successive wash of four.
- pH 5 IC-alum+CC_wash1(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 5. First successive wash of four.
- pH 5 IC-alum+CC_wash2(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 5. Second successive wash of four.
- pH 5 IC-alum+CC_wash3(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 5. Third successive wash of four.
- pH 5 IC-alum+CC_wash4(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 5. Fourth successive wash of four.
- pH 7 IC-alum+CC_wash1(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 7. First successive wash of four.
- pH 7 IC-alum+CC_wash2(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 7. Second successive wash of four.
- pH 7 IC-alum+CC_wash3(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 7. Third successive wash of four.
- pH 7 IC-alum+CC_wash4(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 7. Fourth successive wash of four.
- pH 8.5 IC-alum+CC_wash1(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 8.5. First successive wash of four.
- pH 8.5 IC-alum+CC_wash2(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 8.5. Second successive wash of four.
- pH 8 IC-alum+CC_wash3(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 8.5. Third successive wash of four.
- pH 8.5 IC-alum+CC_wash4(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with indigo carmine (IC) soaked in water adjusted to pH 8.5. Fourth successive wash of four.
File: Washfastness-Madder-Indigo_pH4-pH5_pH7_pH8.5_UVVis_raw-data.csv
Description: UV-Visible absorbance spectral data for pH-dependent wash fastness data for wool samples dyed with madder and indigo. Wool dyed with madder was pre-treated with alum and cream of tartar before dyeing, and wool dyed with indigo was not pretreated prior to dyeing. The washfastness of the madder and indigo dyed wool samples were tested by washing the sample a total of four successive times. This process was done using water adjusted to four different pH values: 4, 5, 7, and 8.5.
Variables
- Wavelength(nm): Wavelength in nanometers at which absorbance data in following rows was collected.
- pH 4 Madder-alum+CC_wash1(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with madder soaked in water adjusted to pH 4. First successive wash of four.
- pH 4 Madder-alum+CC_wash2(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with madder soaked in water adjusted to pH 4. Second successive wash of four.
- pH 4 Madder-alum+CC_wash3(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with madder soaked in water adjusted to pH 4. Third successive wash of four.
- pH 4 Madder-alum+CC_wash4(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with madder soaked in water adjusted to pH 4. Fourth successive wash of four.
- pH 5 Madder-alum+CC_wash1(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with madder soaked in water adjusted to pH 5. First successive wash of four.
- pH 5 Madder-alum+CC_wash2(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with madder soaked in water adjusted to pH 5. Second successive wash of four.
- pH 5 Madder-alum+CC_wash3(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with madder soaked in water adjusted to pH 5. Third successive wash of four.
- pH 5 Madder-alum+CC_wash4(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with madder soaked in water adjusted to pH 5. Fourth successive wash of four.
- pH 7 Madder-alum+CC_wash1(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with madder soaked in water adjusted to pH 7. First successive wash of four.
- pH 7 Madder-alum+CC_wash2(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with madder soaked in water adjusted to pH 7. Second successive wash of four.
- pH 7 Madder-alum+CC_3 2(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with madder soaked in water adjusted to pH 7. Third successive wash of four.
- pH 7 Madder-alum+CC_wash4(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with madder soaked in water adjusted to pH 7. Fourth successive wash of four.
- pH 8.5 Madder-alum+CC_wash1(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with madder soaked in water adjusted to pH 8.5. First successive wash of four.
- pH 8.5 Madder-alum+CC_wash2(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with madder soaked in water adjusted to pH 8.5. Second successive wash of four.
- pH 8.5 Madder-alum+CC_wash3(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with madder soaked in water adjusted to pH 8.5. Third successive wash of four.
- pH 8.5 Madder-alum+CC_wash4(Abs): Absorbance data of wool (pre-treated with a alum and cream of tartar solution prior to dyeing) dyed with madder soaked in water adjusted to pH 8.5. Fourth successive wash of four.
- pH 4 indigo-no-pretreatment_1(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo soaked in water adjusted to pH 4. First successive wash of four.
- pH4 indigo-no-pretreatment_wash2(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo soaked in water adjusted to pH 4. Second successive wash of four.
- pH 4 indigo-no-pretreatment_wash3(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo soaked in water adjusted to pH 4. Third successive wash of four.
- pH 4 indigo-no-pretreatment_wash4(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo soaked in water adjusted to pH 4. Fourth successive wash of four.
- pH 5 indigo-no-pretreatment_wash1(Abs):Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo soaked in water adjusted to pH 5. First successive wash of four.
- pH5 indigo-no-pretreatment_wash2(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo soaked in water adjusted to pH 5. Second successive wash of four.
- pH 5 indigo-no-pretreatment_3 2(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo soaked in water adjusted to pH 5. Third successive wash of four.
- pH 5 indigo-no-pretreatment_wash4(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo soaked in water adjusted to pH 5. Fourth successive wash of four.
- pH 7 indigo-no-pretreatment_wash1(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo soaked in water adjusted to pH 7. First successive wash of four.
- pH7 indigo-no-pretreatment_wash2(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo soaked in water adjusted to pH 7. Second successive wash of four.
- pH 7 indigo-no-pretreatment_wash3(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo soaked in water adjusted to pH 7. Third successive wash of four.
- pH 7 indigo-no-pretreatment_4 2(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo soaked in water adjusted to pH 7. Fourth successive wash of four.
- pH 8.5 indigo-no-pretreatment_wash1(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo soaked in water adjusted to pH 8.5. First successive wash of four.
- pH8.5 indigo-no-pretreatment_wash2(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo soaked in water adjusted to pH 8.5. Second successive wash of four.
- pH 8.5 indigo-no-pretreatment_wash3(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo soaked in water adjusted to pH 8.5. Third successive wash of four.
- pH 8.5 indigo-no-pretreatment_wash4(Abs): Absorbance data of wool (no pre-treatment prior to dyeing) dyed with indigo soaked in water adjusted to pH 8.5. Fourth successive wash of four.
File: Few-fiber_pH5_pH8.5_microextraction_UVVis_raw-data.csv
Description: UV-Visible absorbance spectral data for pH-dependent wash fastness data for few fiber wool dyed with indigo carmine. The number of fibers were first soaked in a pH 5 solution, dried, and then subsequently soaked in a pH 8.5 solution.
Variables
- Wavelength (nm): Wavelength in nanometers at which absorbance data in following rows was collected.
- Absorbance_6_threads-pH5: UV-Visible Absorbance data after washing 6 wool fibers dyed with indigo carmine (approx 4-6 mm in length) in water adjusted to pH 5.
- Absorbance_6_threads-pH8.5: UV-Visible Absorbance data after washing 6 wool fibers dyed with indigo carmine (same sample as pH 5 wash) in a pH 8.5 wash solution.
- Absorbance_8_threads_pH5: UV-Visible Absorbance data after washing 8 wool fibers dyed with indigo carmine (approx 4-6 mm in length) in water adjusted to pH 5.
- Absorbance_8_threads_pH8.5: UV-Visible Absorbance data after washing 8 wool fibers dyed with indigo carmine (same sample as pH 5 wash) in a pH 8.5 wash solution.
- Absorbance_10_threads_pH5: UV-Visible Absorbance data after washing 10 wool fibers dyed with indigo carmine (approx 4-6 mm in length) in water adjusted to pH 5.
- Absorbance_10_threads_pH8.5: UV-Visible Absorbance data after washing 10 wool fibers dyed with indigo carmine (same sample as pH 5 wash) in a pH 8.5 wash solution.
- Absorbance_12_threads_pH5: UV-Visible Absorbance data after washing 12 wool fibers dyed with indigo carmine (approx 4-6 mm in length) in water adjusted to pH 5.
- Absorbance_12_threads_pH8.5: UV-Visible Absorbance data after washing 12 wool fibers dyed with indigo carmine (same sample as pH 5 wash) in a pH 8.5 wash solution.
- Absorbance_14_threads_pH5: UV-Visible Absorbance data after washing 14 wool fibers dyed with indigo carmine (approx 4-6 mm in length) in water adjusted to pH 5.
- Absorbance_14_threads_pH8.5: UV-Visible Absorbance data after washing 14 wool fibers dyed with indigo carmine (same sample as pH 5 wash) in a pH 8.5 wash solution.
- Absorbance_16_threads_pH5: UV-Visible Absorbance data after washing 16 wool fibers dyed with indigo carmine (approx 4-6 mm in length) in water adjusted to pH 5.
- Absorbance_16_threads_pH8.5: UV-Visible Absorbance data after washing 16 wool fibers dyed with indigo carmine (same sample as pH 5 wash) in a pH 8.5 wash solution.
File: Historical-textiles_pH5_pH8.5_microextraction_UVVis_raw-data.csv
Description: UV-Visible absorbance spectral data for pH-dependent microextraction data for historical textile samples.
Variables
- Wavelength(nm): Wavelength in nanometers at which absorbance data in following rows was collected.
- Absorbance_52814#3_pH5: UV-Visible Absorbance data after washing historical sample (collection reference number 52814) in water adjusted to pH 5.
- Absorbance_52814#3_pH8.5: UV-Visible Absorbance data after washing historical sample (collection reference number 52814) in water adjusted to pH 8.5.
- Absorbance_1985.23.23#8_pH5: UV-Visible Absorbance data after washing historical sample (collection reference number 1985.23.23) in water adjusted to pH 5.
- Absorbance_1985.23.23#8_pH8.5: UV-Visible Absorbance data after washing historical sample (collection reference number 1985.23.23) in water adjusted to pH 8.5.
- Absorbance_1998.225.2#14_pH5: UV-Visible Absorbance data after washing historical sample (collection reference number 1998.225.2) in water adjusted to pH 5.
- Absorbance_1998.225.2#14_pH8.5: UV-Visible Absorbance data after washing historical sample (collection reference number 1998.225.2) in water adjusted to pH 8.5.
- Absorbance_1998.225.2#16_pH5: UV-Visible Absorbance data after washing historical sample (collection reference number 1998.225.2) in water adjusted to pH 5.
- Absorbance_1998.225.2#16_pH8.5: UV-Visible Absorbance data after washing historical sample (collection reference number 1998.225.2) in water adjusted to pH 8.5.
Access information
n/a
Preliminary pH-dependent wash fastness tests: Each wool fabric sample was cut to weigh approximately 12-15 mg (approximately 1 cm2 in size) for wash fastness tests. The cut samples were washed in 5 mL of corresponding pH-adjusted H2O solutions for 90 minutes in 15 mL polypropylene centrifuge tubes. After soaking, the samples were removed, dried on a stainless-steel mesh wire, and the resultant solution was analyzed for indigo carmine by measuring the absorbance at its maximum wavelength (λmax = 611 nm) by UV-Vis absorbance spectroscopy.
Few-fiber tests: a typical sample consisted of a minimum of 6 individual wool fibers measuring approximately 4-6 mm in length. Historical wool samples were isolated under a microscope following these criteria. First, a 100 μL aliquot of the DI water (pH 5) water was placed in the cap removed from the top of a 1.5 mL polypropylene microcentrifuge tube. Fibers were transferred to the water using fine tweezers and gently immersed in the solution to ensure all fibers were fully submerged during soaking. The cap was placed within an enclosed Petri dish to limit evaporation, and samples were exposed to the solution for 90 minutes. The extract was then transferred to a 40 uL volume quartz cell microcuvette with a 10 mm path length (Starna Cells, Catalog number# 16.40-Q-10/Z8.5) and the absorbance of the solution was measured by UV-Visible spectroscopy. The isolated fibers were then washed in DI water adjusted to pH 8.5, and the same process as above was repeated.
Historical textile fiber samples were tested using the same method as the few-fiber samples described above.
UV-Visible absorbance (UV-Vis) measurements were conducted using a Thermo Scientific Genesys 150 Spectrophotometer. The spectrometer was set to a measurement range of 400-800 nm with a medium scan speed and a 1.0 nm wavelength interval for all measurements. Data was exported as a .csv file from the instrument and processed using Microsoft Excel.