Papers by Lina Falcão
Molecules, 2018
In this review, a brief description of how animal skins were transformed in leathers in Europe us... more In this review, a brief description of how animal skins were transformed in leathers in Europe using different vegetable tannins will be presented. Special attention will be dedicated to the description of the type of tannins and the characteristics of the most important type of historic leathers thus obtained. The text will also focus on the description of the techniques used in the identification of these tannins in historic objects: colorimetric tests and spectroscopic analysis.
Conservar Património, 2018
Neste artigo apresenta-se o estudo químico dos taninos usados na curtimenta vegetal de duas tipol... more Neste artigo apresenta-se o estudo químico dos taninos usados na curtimenta vegetal de duas tipologias de cabedais históricos e decorativos europeus pertencentes a acervos de colecções portuguesas, os cabedais adamascados e os guadamecis, datados dos séculos XVII e XVIII. Foram analisados extractos preparados a partir de fibras recolhidas nesses cabedais através da técnica de espectroscopia de infravermelho com transformada de Fourier (FTIR) em modo de reflectância total atenuada (ATR). Os resultados obtidos foram comparados com os dados de diversas amostras de referência de taninos que, de acordo com fontes documentais, se encontravam, na generalidade, em uso na Europa na Idade Moderna. Este estudo permitiu caracterizar, na maioria dos casos, os taninos utilizados na produção dos cabedais estudados e, paralelamente, detectar uma alteração química dos cabedais, neste caso a hidrólise do colagénio, a qual não era perceptível visualmente.
Vibrational Spectroscopy, 2014
Tanning materials of historic leather samples collected from the 19th century Portuguese Royal tr... more Tanning materials of historic leather samples collected from the 19th century Portuguese Royal train were analyzed by attenuated total reflection–Fourier transform infrared (ATR–FTIR) spectroscopy. Studied leathers were visually identified as morocco leathers, one of the most valued types of vegetable tanned leathers. In technical and historic literature, morocco leathers are described as a distinctive type of vegetable tanned leather, with a typical grain surface pattern, made from goat skins and sumac (Rhus coriaria) leaves.
ATR–FTIR spectra of the Royal train leathers were investigated and compared with 10 reference tanning materials obtained from different plants in use in the 19th century, here described. Two different types of vegetable tanned leathers were identified. The obtained spectra allowed to confirm the presence of morocco leathers as well as to detect a different type of vegetable tanned leather, probably applied as a restoration material in a past intervention. This study shows the usefulness of ATR–FTIR to distinguish different types of historic leathers based in the spectroscopic characteristic IR bands of vegetable tannins used for leather production, which can be of great assistance for conservation condition assessments.
Journal of Cultural Heritage, 2013
This paper presents a complementary analytical approach to characterize vegetable tanning materia... more This paper presents a complementary analytical approach to characterize vegetable tanning materials in historic leathers. It is described the application of two molecular spectroscopic techniques, ATR-FTIR and UV-Vis, and three specific chemical tests to analyse tannins present in leathers. Acid butanol, nitrous acid and rhodanine colorimetric tests, evaluated both visually and spectrophotometrically, were used to identify condensed tannins, ellagitannins and gallotannins, respectively. Ten samples of commercial, or laboratory prepared, vegetable tannins and seven new vegetable tanned leathers were also analysed and obtained results were used for comparison. The complete analytical procedure was performed, in a semi-micro-destructive scale, using fibres collected from leather. Analysis of ATR-FTIR and UV spectra of commercial and laboratory prepared vegetable tannins allowed the establishment of the characteristic bands of condensed and hydrolysable tannins and, more specifically, gallotannins. These data were used to confirm the type of vegetable tanning agents used in new leather extracts. The same approach was used in cultural heritage leathers, supported by the colorimetric tests, since protein degradation products were co-extracted in aged leathers and interfered in IR spectra.
Journal of Cultural Heritage, 2011
This paper describes the adaptation and evaluation of three chemical tests for tannins characteri... more This paper describes the adaptation and evaluation of three chemical tests for tannins characterisation in vegetable tanned leathers. Tests were performed on fibres of new leathers tanned with different known vegetable tannins and historic leathers. Rhodanine test, nitrous acid test and acid butanol test, developed to identify, respectively, gallotannins, ellagitannins and condensed tannins, are described. Ferric test and vanillin test, the two traditional tests used for vegetable tanned leathers characterisation, were also performed and their usefulness discussed. Gallic acid, ellagic acid and catechin, structural constituents of the different classes of tannins were also tested. Results of the developed methodology allowed the identification of tannins’ chemical class in new and historic leather samples studied. Data obtained permitted to verify the information on tanning materials used in new leathers. Vegetable tanning technology was confirmed in historic samples and tannins were characterised. This study shows that these tests are useful and can be a valuable source of information to evaluate new vegetable tanned leathers quality for conservation and restoration purposes as well as historic leathers tanning technology.
Conference Presentations by Lina Falcão
Between the 17 th and 18 th centuries a distinctive type of decorative historic leather was produ... more Between the 17 th and 18 th centuries a distinctive type of decorative historic leather was produced in Portugal: tooled leather. It was used as a luxurious covering material in seating furniture, day beds and chests. The decoration was obtained by hammering different small metallic blind tools over the grain layer of the leather. The traditional type of leather used was a thick (≈5-6 mm) and rigid vegetable tanned leather, similar to sole leather. In this communication it is presented the application of ATR-FTIR to analyse tannins extracted from tooled leathers from Portuguese museum collections. The purpose of this study was the detection and identification of the vegetable tanning materials used in leather making. This information is important to understand not only leather composition and technology but also degradation susceptibility or condition which is valuable to carry out suitable conservation treatments. Aqueous acetone extracts were prepared from 45 leather samples (fibres from the flesh layer) collected from furniture in exhibition of different Portuguese museum collections.
Morocco leathers are sumac tanned goatskins with a characteristic uniform grain pattern which hav... more Morocco leathers are sumac tanned goatskins with a characteristic uniform grain pattern which have been widely used, at least since the 15th century, for bookbinding, footwear, gloving, upholstery or covering cases, coffers and other decorative valuable artifacts. Originally, these leathers were imported into Europe from North of Africa, hence the name, or eastern Mediterranean. Although morocco leather production has been introduced by Moors in Iberian Peninsula in the Middle Ages, only during the mid 18th century this type of leather started to be produced in France and Britain. Commonly, this type of leather presents the grain layer (outer layer of the skin) dyed.
Vegetable tanning materials of two morocco leathers dated from mid-19th century were studied by ATR-FTIR and UV-Vis spectroscopies. Both leather were applied as capitoné upholstery covering material in seating furniture, one in a gilded day-bed (National Palace of Ajuda, Lisbon, Portugal) and the other in a wing-chair from the Portuguese Royal train (National Railway Museum, Entroncamento, Portugal) which have belonged to King Luis I of Portugal (1861-1889). Vegetable tanning materials were extracted from corium leather fibres with aqueous-acetone (1:1, ppv).
In this communication, ATR-FTIR and UV-Vis spectra of leather extracts are presented and compared different types of vegetable tanning materials. Spectra showed a similar absorption pattern to sumac leaves extract and tannic acid, both described in literature as gallotannins, which is in agreement historical documentation.
Tannins, extracted from barks, leaves, wood or galls, are polyphenolic plant secondary metabolite... more Tannins, extracted from barks, leaves, wood or galls, are polyphenolic plant secondary metabolites which have been employed since Neolithic time to transform putrescible animal skins into leather. These leathers are known as vegetable tanned leathers and are the most common in European cultural heritage. Tannins can be classified in two main groups: condensed (or proanthocyanidins and examples are mimosa and quebracho) and hydrolysable tannins. Last group is sub-classified in gallotannins (examples are sumac and tara) and ellagitannins (examples are chestnut and valonia)[1]. In this study[2] three colorimetric and chemical tests, based on acid butanol, nitrous acid and rhodanine assays, developed to analyse respectively, gallotannins, ellagitannins and proanthocyanidins[3], were adapted to be used as spot tests to detect tannins in small amounts (≈15 mg) of historic leather fibres. A -19th century morocco upholstery leather B -19th century upholstery leather C -19th century bookbinding leather D -18th century gilt leather
Tannins, extracted from barks, leaves, wood or galls, are polyphenolic plant secondary metabolite... more Tannins, extracted from barks, leaves, wood or galls, are polyphenolic plant secondary metabolites which have been employed for many thousands of years to convert animal skins into leather . These leathers are known as vegetable tanned leathers. The properties that tannins confer to the leather are as varied as the different sources from which they are extracted . Depending on their chemical composition, tannins can be classified in two main groups: condensed (proanthocyanidins) and hydrolysable tannins. Last group is sub-classified in gallotannins and ellagitannins . Vegetable tanned leathers are the most common in cultural heritage and frequently need conservation and restoration . Treatments such rebinding, loss compensations or reinforcements often require the application of new leathers as restoration material. Past studies and recent conservation science research showed that leathers tanned with hydrolysable tannins are less prone to deterioration than those tanned with condensed tannins. Thus, for conservation and restoration purposes, only leathers tanned with hydrolysable tannins, such as sumac, chestnut, tara or valonea tannins, are recommended [5] . Conservation and restoration work on 17th century Portuguese leather upholsteries, from armchairs of Paço dos Duques palace (Guimarães), required a suitable hydrolysable type of leather to fill missing areas. A present-day commercial vegetable tanned leather, supplied as chesnut leather (ellagitannin type), was considered a good choice to be used as restoration material. To confirm vegetable tannage, leather was studied by UV and FTIR spectroscopies. Spectroscopic analysis were complemented with chemical assays.
Book chapters by Lina Falcão
Conference Proceedings by Lina Falcão
A Charola do Convento de Cristo apresenta em diversos locais pequenas áreas da superfície mural p... more A Charola do Convento de Cristo apresenta em diversos locais pequenas áreas da superfície mural pétrea decorada com guadamecil, uma tipologia de cabedal decorativo e artístico europeu. Estes são os guadamecis mais antigos conhecidos em Portugal que ainda permanecem no local de origem e, considerando a sua decoração gravada e policromada com os símbolos manuelinos, como a Esfera Armilar e a Cruz da Ordem de Cristo, podem ser datados das primeiras décadas do século XVI, época das campanhas ornamentais encomendadas por D. Manuel I.
Nesta comunicação, para além de se enunciarem as características singulares dos guadamecis da Charola, raras no património cultural português e europeu, apresenta-se uma breve contextualização histórica e tecnológica desta arte europeia. São ainda abordados os principais problemas do estado de conservação encontrados, bem como as acções de conservação desenvolvidas para preservar esses revestimentos únicos.
Abstract in English:
The Charola in the Convent of Christ presents small areas of the stonewall surface decorated with gilt leather (guadamecil), a type of European decorative and artistic leather. These gilt leather coverings are the oldest known in Portugal that still remain in the place of origin and considering the engraved and painted decorative patterns related to the heraldry of the Portuguese King Manuel I, such as the Armillary Sphere and the Order of Christ Cross, these leathers were placed in the Charola during the Manuelin ornamental campaigns, in the first decades of the 16th century.
In this paper it is presented a description of the characteristics of the Charola gilt leather, rare in the Portuguese and European cultural heritage, as well as a brief history of this decorative art. Gilt leather condition and the conservation treatment carried out to preserve these unique coverings are also presented.
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Papers by Lina Falcão
ATR–FTIR spectra of the Royal train leathers were investigated and compared with 10 reference tanning materials obtained from different plants in use in the 19th century, here described. Two different types of vegetable tanned leathers were identified. The obtained spectra allowed to confirm the presence of morocco leathers as well as to detect a different type of vegetable tanned leather, probably applied as a restoration material in a past intervention. This study shows the usefulness of ATR–FTIR to distinguish different types of historic leathers based in the spectroscopic characteristic IR bands of vegetable tannins used for leather production, which can be of great assistance for conservation condition assessments.
Conference Presentations by Lina Falcão
Vegetable tanning materials of two morocco leathers dated from mid-19th century were studied by ATR-FTIR and UV-Vis spectroscopies. Both leather were applied as capitoné upholstery covering material in seating furniture, one in a gilded day-bed (National Palace of Ajuda, Lisbon, Portugal) and the other in a wing-chair from the Portuguese Royal train (National Railway Museum, Entroncamento, Portugal) which have belonged to King Luis I of Portugal (1861-1889). Vegetable tanning materials were extracted from corium leather fibres with aqueous-acetone (1:1, ppv).
In this communication, ATR-FTIR and UV-Vis spectra of leather extracts are presented and compared different types of vegetable tanning materials. Spectra showed a similar absorption pattern to sumac leaves extract and tannic acid, both described in literature as gallotannins, which is in agreement historical documentation.
Book chapters by Lina Falcão
Conference Proceedings by Lina Falcão
Nesta comunicação, para além de se enunciarem as características singulares dos guadamecis da Charola, raras no património cultural português e europeu, apresenta-se uma breve contextualização histórica e tecnológica desta arte europeia. São ainda abordados os principais problemas do estado de conservação encontrados, bem como as acções de conservação desenvolvidas para preservar esses revestimentos únicos.
Abstract in English:
The Charola in the Convent of Christ presents small areas of the stonewall surface decorated with gilt leather (guadamecil), a type of European decorative and artistic leather. These gilt leather coverings are the oldest known in Portugal that still remain in the place of origin and considering the engraved and painted decorative patterns related to the heraldry of the Portuguese King Manuel I, such as the Armillary Sphere and the Order of Christ Cross, these leathers were placed in the Charola during the Manuelin ornamental campaigns, in the first decades of the 16th century.
In this paper it is presented a description of the characteristics of the Charola gilt leather, rare in the Portuguese and European cultural heritage, as well as a brief history of this decorative art. Gilt leather condition and the conservation treatment carried out to preserve these unique coverings are also presented.
ATR–FTIR spectra of the Royal train leathers were investigated and compared with 10 reference tanning materials obtained from different plants in use in the 19th century, here described. Two different types of vegetable tanned leathers were identified. The obtained spectra allowed to confirm the presence of morocco leathers as well as to detect a different type of vegetable tanned leather, probably applied as a restoration material in a past intervention. This study shows the usefulness of ATR–FTIR to distinguish different types of historic leathers based in the spectroscopic characteristic IR bands of vegetable tannins used for leather production, which can be of great assistance for conservation condition assessments.
Vegetable tanning materials of two morocco leathers dated from mid-19th century were studied by ATR-FTIR and UV-Vis spectroscopies. Both leather were applied as capitoné upholstery covering material in seating furniture, one in a gilded day-bed (National Palace of Ajuda, Lisbon, Portugal) and the other in a wing-chair from the Portuguese Royal train (National Railway Museum, Entroncamento, Portugal) which have belonged to King Luis I of Portugal (1861-1889). Vegetable tanning materials were extracted from corium leather fibres with aqueous-acetone (1:1, ppv).
In this communication, ATR-FTIR and UV-Vis spectra of leather extracts are presented and compared different types of vegetable tanning materials. Spectra showed a similar absorption pattern to sumac leaves extract and tannic acid, both described in literature as gallotannins, which is in agreement historical documentation.
Nesta comunicação, para além de se enunciarem as características singulares dos guadamecis da Charola, raras no património cultural português e europeu, apresenta-se uma breve contextualização histórica e tecnológica desta arte europeia. São ainda abordados os principais problemas do estado de conservação encontrados, bem como as acções de conservação desenvolvidas para preservar esses revestimentos únicos.
Abstract in English:
The Charola in the Convent of Christ presents small areas of the stonewall surface decorated with gilt leather (guadamecil), a type of European decorative and artistic leather. These gilt leather coverings are the oldest known in Portugal that still remain in the place of origin and considering the engraved and painted decorative patterns related to the heraldry of the Portuguese King Manuel I, such as the Armillary Sphere and the Order of Christ Cross, these leathers were placed in the Charola during the Manuelin ornamental campaigns, in the first decades of the 16th century.
In this paper it is presented a description of the characteristics of the Charola gilt leather, rare in the Portuguese and European cultural heritage, as well as a brief history of this decorative art. Gilt leather condition and the conservation treatment carried out to preserve these unique coverings are also presented.