A Study on the Degradation of Iron Gall Inks and to Preserve Them Using Green Approaches
Abstract
1. Introduction
1.1. Relevance of Iron-Gall Inks
1.2. New Formulations Disclosed in the Past Through the Use of Historically Accurate Reconstructions for Iron Gall Inks
1.3. The Preservation of a Diversity of Iron Gall Inks
1.4. Main Degradation Products of Iron Gall Inks
1.5. How to Preserve Iron Gall Inks Using a Green Approach
2. Materials and Methods
2.1. Preparation of the Extracts and Inks
- The main steps and ingredients used to prepare the recipes. RT is room temperature.
Water | Others | Galls | FeSO4 | Extraction | pH | ||
Extr. | Final | ||||||
Braga | 99 mL | 49.8 mL vinegar | 9.36 g | 37.5 g FeSO4 | Boiling and reduced to 1/3 | 2.84 | 1.73 |
Montpellier | 200 mL | 5.72 g | 3.8 g FeSO4 | 3 days at RT Boiling and reduced to ¼ Filtration | 3.39 | 2.51 | |
Guadalupe | 37.5 mL | 12.5 mL white wine | 5.6 g | 3.75 g FeSO4 1.87 g CuSO4 | 6 days at RT Aquece 10 min Filtration | 3.56 | 2.47 |
Madrid | - | 50 mL white wine | 2.76 g | 2.76 g FeSO4 0.22 g Al3+, indigo, sugar | 6 days at RT Filtration | 3.18 | 2.31 |
QI.8 | 50 mL | - | 2.5 g | 2.5 g FeSO4 | 4 days at RT Filtration | 3.86 | 2.29 |
QI.9 | 75 mL | - | 6.15 g | 4.95 g FeSO4 | 24 h at RT Boiling and reduced to 2/3 Filtration | 3.81 | 2.30 |
2.2. Aging
2.3. HPLC–DAD and HPLC–ESI–MS
2.4. Colorimetry
2.5. Microscopy
2.6. Micro-Infrared Spectroscopy
2.7. Micro-Raman Spectroscopy
2.8. Preparation of the Gels
3. Results and Discussion
3.1. Aging of the Iron Gall Inks
3.2. Quantification of the Polyphenols Identified in the Inks by HPLC–DAD
3.3. Infrared Spectra by Micro-Fourier Transform Infrared Spectroscopy
3.4. Raman Spectra by Micro-Raman Spectroscopy
3.5. Colorimetry Through L* a* b* Coordinates
3.6. Novel Green Approaches
3.6.1. First Experimentation
3.6.2. Cleaning Inks Through a Safe Approach
4. Conclusions
Supplementary Materials
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Recipe | [Gallic Acid] | [PGG + HxGG] | Phenolic Compounds | % [Gallic Acid]/ Phenolic Compounds | % [PGG + HxGG]/ Phenolic Compounds |
---|---|---|---|---|---|
Braga | 1.9 ± 0.6 | 15 ± 2 | 26 ± 3 | 7.7 ± 0.9 | 56 ± 2 |
Montpellier | 5 ± 1 | 11 ± 1 | 27± 2 | 18 ± 2 | 40 ± 6 |
Córdoba | 5 ± 1 | 0.15 ± 0.01 | 7 ± 4 | 65 ± 3 | 2.1 ± 0.8 |
Guadalupe | 4 ± 1 | 32 ± 3 | 51± 4 | 8 ± 1 | 62 ± 3 |
Madrid | 1.00 ± 0.04 | 11.5 ± 0.5 | 17.8 ± 0.6 | 5.6 ± 0.3 | 65 ± 1 |
QI.8 | 0.202 ± 0.002 | 1.94 ± 0.05 | 2.43 ± 0.07 | 8.3 ± 0.2 | 79.9 ± 0.2 |
QI.9 | 0.2085 ± 0.0009 | 2.250 ± 0.007 | 2.89 ± 0.02 | 7.22 ± 0.05 | 77.9 ± 0.5 |
Recipe | Irradiation Time | Gallic Acid | PGG + HxGG + HpGG | Phenolic Compounds | % [Gallic Acid]/Phenolic Compounds | % [PGG + HxGG + HpGG]/Phenolic Compounds |
---|---|---|---|---|---|---|
Braga | 0 h | 3.047 ± 0.006 | 9.5 ± 0.2 | 16.5 ± 0.3 | 18.4 ± 0.3 | 57 ± 2 |
20 h | 2.31 ± 0.02 | 2.3 ± 0.2 | 6.5 ± 0.3 | 36 ± 2 | 35 ± 3 | |
40 h | 2.27 ± 0.01 | 0.93 ± 0.08 | 4.6 ± 0.1 | 50 ± 1 | 20 ± 2 | |
60 h | 2.138 ± 0.008 | 1.95 ± 0.06 | 5.7 ± 0.1 | 37.8 ± 0.7 | 35 ± 1 | |
78 h | 1.70 ± 0.02 | 1.09 ± 0.03 | 4.16 ± 0.07 | 40.9 ± 0.8 | 26 ± 1 | |
100 h | 1.62 ± 0.04 | 0.5 ± 0.2 | 3.3 ± 0.4 | 49 ± 6 | 16 ± 6 | |
172 h | 1.231 ± 0.004 | 0.12 ± 0.04 | 2.3 ± 0.2 | 53 ± 4 | 5 ± 2 | |
196 h | 1.30 ± 0.01 | 0.08 ± 0.02 | 2.60 ± 0.07 | 50 ± 1 | 3.1 ± 0.6 | |
220 h | 0.906 ± 0.004 | 0.140 ± 0.004 | 1.83 ± 0.03 | 49.5 ± 0.8 | 7.7 ± 0.2 | |
260 h | 0.867 ± 0.002 | 0.007 ± 0.004 | 1.65 ± 0.03 | 53 ± 1 | 0.4 ± 0.3 | |
336 h | 0.306 ± 0.006 | nd * | 0.44 ± 0.02 | 70 ± 3 | nd * | |
Córdoba | 0 h | 5.00 ± 0.02 | 3.91 ± 0.06 | 11.3 ± 0.2 | 44.0 ± 0.7 | 34.4 ± 0.7 |
20 h | 3.16 ± 0.04 | 1.05 ± 0.01 | 5.0 ± 0.1 | 64 ± 2 | 21.0 ± 0.5 | |
40 h | 3.37 ± 0.03 | 0.89 ± 0.01 | 5.24 ± 0.08 | 64 ± 1 | 17.0 ± 0.4 | |
60 h | 3.74 ± 0.01 | 1.14 ± 0.02 | 6.12 ± 0.06 | 61.2 ± 0.6 | 18.7 ± 0.3 | |
78 h | 2.47 ± 0.03 | 0.96 ± 0.04 | 4.5 ± 0.1 | 55 ± 2 | 21 ± 1 | |
100 h | 2.63 ± 0.01 | 0.67 ± 0.01 | 4.54 ± 0.07 | 58.1 ± 0.9 | 14.8 ± 0.3 | |
172 h | 1.77 ± 0.03 | 0.26 ± 0.05 | 2.9 ± 0.1 | 60 ± 3 | 9 ± 2 | |
196 h | 1.77 ± 0.01 | 0.51 ± 0.02 | 3.36 ± 0.05 | 52.8 ± 0.9 | 15.2 ± 0.6 | |
220 h | 1.83 ± 0.02 | 0.91 ± 0.03 | 4.3 ± 0.1 | 43 ± 1 | 21.4 ± 0.9 | |
260 h | 3.21 ± 0.03 | 0.67 ± 0.01 | 5.22 ± 0.06 | 61.5 ± 0.9 | 12.9 ± 0.3 |
Recipe | Irradiation Time | Gallic Acid | PGG + HxGG + HpGG | Phenolic Compounds | % [Gallic Acid]/Phenolic Compounds | % [PGG + HxGG + HpGG]/Phenolic Compounds |
---|---|---|---|---|---|---|
Guadalupe | 0 h | 1.975 ± 0.009 | 16.0 ± 0.2 | 21.7 ± 0.3 | 9.1 ± 0.1 | 74 ± 1 |
20 h | 1.42 ± 0.03 | 7.0 ± 0.2 | 9.7 ± 0.3 | 14.6 ± 0.6 | 72 ± 3 | |
40 h | 1.467 ± 0.007 | 7.27 ± 0.06 | 10.5 ± 0.1 | 13.9 ± 0.2 | 69 ± 1 | |
60 h | 1.31 ± 0.03 | 6.5 ± 0.1 | 9.3 ± 0.2 | 14.2 ± 0.4 | 70 ± 2 | |
78 h | 1.21 ± 0.01 | 6.6 ± 0.1 | 9.5 ± 0.2 | 12.8 ± 0.3 | 70 ± 2 | |
100 h | 1.575 ± 0.003 | 8.2 ± 0.2 | 12.0 ± 0.2 | 13.1 ± 0.2 | 68 ± 2 | |
172 h | 1.771 ± 0.005 | 8.4 ± 0.1 | 12.8 ± 0.2 | 13.8 ± 0.2 | 66 ± 1 | |
196 h | 1.58 ± 0.02 | 6.99 ± 0.09 | 10.9 ± 0.2 | 14.4 ± 0.3 | 64 ± 1 | |
220 h | 1.29 ± 0.02 | 5.19 ± 0.09 | 8.6 ± 0.2 | 15.0 ± 0.4 | 61 ± 2 | |
260 h | 1.147 ± 0.008 | 3.53 ± 0.03 | 6.17 ± 0.09 | 18.6 ± 0.3 | 57.2 ± 0.9 | |
336 h | 0.581 ± 0.003 | 1.93 ± 0.04 | 3.46 ± 0.06 | 16.8 ± 0.3 | 56 ± 2 | |
Montpellier | 0 h | 7.06 ± 0.04 | 7.2 ± 0.2 | 27.7 ± 0.4 | 25.5 ± 0.4 | 26.0 ± 0.8 |
20 h | 6.02 ± 0.04 | 3.35 ± 0.06 | 15.1 ± 0.2 | 39.8 ± 0.7 | 22.2 ± 0.5 | |
40 h | 5.71 ± 0.04 | 2.20 ± 0.02 | 12.0 ± 0.1 | 47.5 ± 0.5 | 18.3 ± 0.2 | |
60 h | 5.76 ± 0.02 | 2.40 ± 0.04 | 13.1 ± 0.2 | 44.1 ± 0.6 | 18.4 ± 0.4 | |
78 h | 5.27 ± 0.08 | 2.03 ± 0.07 | 11.2 ± 0.3 | 47 ± 1 | 18.1 ± 0.8 | |
100 h | 5.67 ± 0.02 | 1.99 ± 0.05 | 11.7 ± 0.2 | 48.4 ± 0.7 | 17.0 ± 0.5 | |
172 h | 6.1684 ± 0.0005 | 2.61 ± 0.02 | 15.26 ± 0.06 | 40.4 ± 0.2 | 17.1 ± 0.2 | |
196 h | 3.342 ± 0.009 | 1.96 ± 0.06 | 10.0 ± 0.1 | 33.6 ± 0.5 | 19.7 ± 0.7 | |
220 h | 5.38 ± 0.01 | 1.35 ± 0.02 | 11.4 ± 0.1 | 47.4 ± 0.6 | 11.9 ± 0.2 | |
260 h | 4.47 ± 0.06 | 0.583 ± 0.007 | 8.0 ± 0.1 | 56 ± 1 | 7.3 ± 0.1 | |
336 h | 4.650 ± 0.004 | 0.293 ± 0.005 | 7.47 ± 0.07 | 62.3 ± 0.6 | 3.92 ± 0.08 |
Braga | Montpellier | Guadalupe | Madrid | QI.8 | QI.9 | Assignments |
---|---|---|---|---|---|---|
759 w | 761 w | 759 w | 757 vw | 750 vw | 760 vw | marker gallotannins |
- | - | - | - | - | - | |
871 w | 870 w | 871 w | 871 vw | 870 vw | 870 vw | marker gallotannins |
1035 sh | 1042 sh | 1035 sh | 1040 sh | 1040 sh | 1040 sh | C-O str vib (ester) |
1090 s | 1094 s | 1090 s | 1093 s | 1092 s | 1091 s | marker gallotannins |
1203 m | 1204 m | 1202 m | 1203 sh | 1204 sh | 1204 sh | C-O str vib (ester) |
1321 m | 1325 m | 1322 m | 1323 m | 1322 m | 1321 m | C-O sym str (ester) |
1446 m | 1449 m | 1448 w | 1448 w | 1448 w | 1446 w | aromatic st vib |
1540 w | 1536 w | 1536 w | 1540 sh | 1536 sh | 1536 sh | n.a. |
1615 m | 1619 m | 1613 m | 1626 m | 1615 m | 1616 m | aromatic str vib |
1704 m | 1692 m | 1708 m | 1711 sh | 1705 sh | 1701 sh | C=O str (ester) |
3352 sh | 3361 sh | 3363 sh | 3353 sh | 3367 sh | 3359 sh | C-H str (polyphenols; gum arabic) |
0h | 693 h | 1959 h | |||||||
---|---|---|---|---|---|---|---|---|---|
Refs | L* | a* | b* | L* | a* | b* | L* | a* | b* |
Braga | 30.8 ± 0.7 | −0.40 ± 0.05 | −1.4 ± 0.1 | 22 ± 2 | −0.2 ± 0.3 | −1.0 ± 0.5 | 23 ± 3 | −0.02 ± 0.2 | 0.2 ± 0.4 |
Montpellier | 28.4 ± 0.8 | 0.27 ± 0.02 | −1.4 ± 0.2 | 30.0 ± 0.6 | 0.7 ± 0.1 | 0.7 ± 0.2 | 32 ± 2 | 0.5 ± 0.2 | 1.9 ± 0.4 |
Guadalupe | 28 ± 2 | −0.5 ± 0.3 | −1.8 ± 0.3 | 23 ± 2 | 0.36 ± 0.07 | −0.3 ± 0.2 | 27 ± 2 | 0.2 ± 0.3 | 1.9 ± 0.6 |
Madrid | 24 ± 1 | 0.4 ± 0.2 | −0.2 ± 0.2 | 22 ± 1 | 0.6 ± 0.2 | −0.3 ± 0.1 | 29 ± 5 | 0.2 ± 0.1 | 1.0 ± 0.5 |
QI.8 | 24 ± 2 | 0.1 ± 0.2 | −3.04 ± 0.04 | 23 ± 4 | 0.11 ± 0.08 | −1.0 ± 0.6 | 23 ± 6 | −0.1 ± 0.2 | 2 ± 2 |
QI.9 | 25 ± 2 | 0.1 ± 0.3 | −2.9 ± 0.7 | 22 ± 1 | 0.6 ± 0.2 | −0.3 ± 0.1 | 23 ± 2 | 0.36 ± 0.07 | −0.3 ± 0.2 |
0h | 693 h | 1959 h | |||||||
---|---|---|---|---|---|---|---|---|---|
Refs | L* | a* | b* | L* | a* | b* | L* | a* | b* |
Braga | 30.8 ± 0.7 | −0.40 ± 0.05 | −1.4 ± 0.1 | 18.4 ± 0.5 | 0.8 ± 0.2 | −4.4 ± 0.6 | 19 ± 3 | 0.5 ± 0.4 | −3.5 ± 0.7 |
Montpellier | 28.4 ± 0.8 | 0.27 ± 0.02 | −1.4 ± 0.2 | 23.7 ± 0.4 | 0.8 ± 0.07 | −0.3 ± 0.3 | 22.7 ± 0.8 | 0.8 ± 0.1 | −0.1 ± 0.2 |
Guadalupe | 28 ± 2 | −0.5 ± 0.3 | −1.8 ± 0.3 | 19 ± 2 | 0.8 ± 0.3 | −1.0 ± 0.2 | 19 ± 2 | 0.3 ± 0.1 | −1.3 ± 0.1 |
Madrid | 24 ± 1 | 0.4 ± 0.2 | −0.2 ± 0.2 | 23 ± 1 | 0.7 ± 0.1 | −2.4 ± 0.3 | 17.4 ± 0.6 | 0.84 ± 0.05 | −2.7 ± 0.1 |
QI.8 | 24 ± 2 | 0.1 ± 0.2 | −3.04 ± 0.04 | 29 ± 2 | 0.20 ± 0.03 | −1.0 ± 0.7 | 31 ± 8 | −0.4 ± 0.5 | −0.2 ± 1.1 |
QI.9 | 25 ± 2 | 0.1 ± 0.3 | −2.9 ± 0.7 | 23 ± 2 | 0.3 ± 0.2 | −1.43 ± 0.08 | 18 ± 2 | 0.4 ± 0.4 | −1.7 ± 0.2 |
Before | After | |||||
---|---|---|---|---|---|---|
L* | a* | b* | L* | a* | b* | |
Montpellier Figure 9 | 32 ±1 | 0.65 ± 0.06 | 2.25 ± 0.05 | 31.3 ± 0.4 | 1.24 ± 0.05 | 2.73 ± 0.04 |
Montpellier Figure 10 | 31.63 ±0.01 | 0.18 ± 0.04 | 1.86 ± 0.07 | 30.3 ± 0.3 | 1.45 ± 0.07 | 2.26 ± 0.05 |
QI.8 | 24.3 ± 0.2 | −0.01 ± 0.02 | −1.04 ± 0.07 | 26.0 ±0.2 | 0.19 ± 0.01 | 0.9 ± 0.1 |
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Teixeira, N.; Nabais, P.; Otero, V.; Díaz Hidalgo, R.J.; Ferretti, M.; Licchelli, M.; Melo, M.J. A Study on the Degradation of Iron Gall Inks and to Preserve Them Using Green Approaches. Heritage 2025, 8, 261. https://doi.org/10.3390/heritage8070261
Teixeira N, Nabais P, Otero V, Díaz Hidalgo RJ, Ferretti M, Licchelli M, Melo MJ. A Study on the Degradation of Iron Gall Inks and to Preserve Them Using Green Approaches. Heritage. 2025; 8(7):261. https://doi.org/10.3390/heritage8070261
Chicago/Turabian StyleTeixeira, Natércia, Paula Nabais, Vanessa Otero, Rafael Javier Díaz Hidalgo, Matteo Ferretti, Maurizio Licchelli, and Maria J. Melo. 2025. "A Study on the Degradation of Iron Gall Inks and to Preserve Them Using Green Approaches" Heritage 8, no. 7: 261. https://doi.org/10.3390/heritage8070261
APA StyleTeixeira, N., Nabais, P., Otero, V., Díaz Hidalgo, R. J., Ferretti, M., Licchelli, M., & Melo, M. J. (2025). A Study on the Degradation of Iron Gall Inks and to Preserve Them Using Green Approaches. Heritage, 8(7), 261. https://doi.org/10.3390/heritage8070261