A Critical Assessment of A-D Strips® Used in Degradation Studies of Artworks Made from Cellulose Acetate in Studies in conservation, Vol.68 N°1-2(2023; January-February) (2023-01-01)

Public ISBD [article]  inStudies in conservation > Vol.68 N°1-2(2023; January-February) (2023-01-01) . - P. 9-17 Titre : A Critical Assessment of A-D Strips® Used in Degradation Studies of Artworks Made from Cellulose Acetate Type de document : texte imprimé Année de publication : 2023 Article en page(s) : P. 9-17 Langues : Anglais (eng) Catégories : Acétate de cellulose -- Détérioration Acide acétique Composés organiques volatils Spectrophotomètres Index. décimale : 7.025 Dommages. Conservation. Protection Résumé : Acid-detecting strips (A-D Strips®) available from the Image Permanence Institute (IPI) and third-party suppliers outside the USA were originally developed to detect volatile acids from deteriorating film stock made from cellulose acetate (CA) by using a five-step colour scale to represent acetic acid concentration. The strips are shown here to be sufficiently sensitive for the detection of acetic acid as a volatile organic compound (VOC) generated by degrading CA in objects in storage. In confined spaces, the local air concentration of VOCs can deviate significantly from background levels due to low air circulation and interaction with solid materials and can be explored by this means. The usefulness of placing a number of A-D Strips® with CA-based artworks stored in closed containers, instead of or during the deployment of SPME fibres to monitor the degradation of these plastics, is assessed critically. The useful level of indicative and semi-quantitative information they can offer in such practical situations is presented. It is proposed that an interpretation of acetic acid concentration on an eight-step colour scale of measurement of b* in CIELAB1976 colour space with a hand-held spectrophotometer, or visual comparison with the IPI-provided colour scale is more useful than a direct calculation of concentration, because placement around stored objects introduces significant measurement errors. This paper gives guidance on the limitations and benefits of using A-D Strips® as a low-cost passive monitoring tool for CA-based objects, whether visibly degraded or not. The guidance is also relevant for monitoring VOCs derived from wood-based crating materials used in museum storage areas, which also generate acetic acid. [article] A Critical Assessment of A-D Strips® Used in Degradation Studies of Artworks Made from Cellulose Acetate [texte imprimé] . - 2023 . - P. 9-17. Langues : Anglais (eng) in Studies in conservation > Vol.68 N°1-2(2023; January-February) (2023-01-01) . - P. 9-17 Catégories : Acétate de cellulose -- Détérioration Acide acétique Composés organiques volatils Spectrophotomètres Index. décimale : 7.025 Dommages. Conservation. Protection Résumé : Acid-detecting strips (A-D Strips®) available from the Image Permanence Institute (IPI) and third-party suppliers outside the USA were originally developed to detect volatile acids from deteriorating film stock made from cellulose acetate (CA) by using a five-step colour scale to represent acetic acid concentration. The strips are shown here to be sufficiently sensitive for the detection of acetic acid as a volatile organic compound (VOC) generated by degrading CA in objects in storage. In confined spaces, the local air concentration of VOCs can deviate significantly from background levels due to low air circulation and interaction with solid materials and can be explored by this means. The usefulness of placing a number of A-D Strips® with CA-based artworks stored in closed containers, instead of or during the deployment of SPME fibres to monitor the degradation of these plastics, is assessed critically. The useful level of indicative and semi-quantitative information they can offer in such practical situations is presented. It is proposed that an interpretation of acetic acid concentration on an eight-step colour scale of measurement of b* in CIELAB1976 colour space with a hand-held spectrophotometer, or visual comparison with the IPI-provided colour scale is more useful than a direct calculation of concentration, because placement around stored objects introduces significant measurement errors. This paper gives guidance on the limitations and benefits of using A-D Strips® as a low-cost passive monitoring tool for CA-based objects, whether visibly degraded or not. The guidance is also relevant for monitoring VOCs derived from wood-based crating materials used in museum storage areas, which also generate acetic acid.

The Permeability of PET by Formic and Acetic Acid Vapors in Studies in conservation, Vol.68 N°3-4(2023; April-May) (2023-04-03)

Public ISBD [article]  inStudies in conservation > Vol.68 N°3-4(2023; April-May) (2023-04-03) . - Pages 458-473 Titre : The Permeability of PET by Formic and Acetic Acid Vapors Type de document : texte imprimé Année de publication : 2023 Article en page(s) : Pages 458-473 Langues : Anglais (eng) Catégories : Acide acétique Conservation et restauration -- Appareils et matériel Encapsulation (chimie) Formique, Acide Papier -- Conservation et restauration -- Recherche Polyéthylène térephtalate -- Perméabilité Revêtement en plastique -- Perméabilité Vapeur, Technique de la Index. décimale : 7.025 Dommages. Conservation. Protection Résumé : ABSTRACT The permeability of biaxially oriented polyethylene terephthalate, PET, to vapors from 5%, 30%, and 100% formic acid solutions as well as the vapor from a 30% acetic acid solution was measured by gravimetric analysis in order to determine the transmission rate of the vapors through PET folders and enclosures made from Mylar™ and similar materials, and ultimately understand the microenvironment that is created inside an encapsulate. The data shows that the permeation of formic acid vapor is at least two orders of magnitude slower than the permeation of water vapor. Measurements of the permeation of 30% acetic acid vapor through PET seemed to be due to the permeation of the water only, and the permeation of the acetic acid, if it occurred, occurred too slowly to be measured. The size of the diffusing molecule determines the permeation. Since the permeability decreases as the size of the diffusing vapor molecule increases, a plot of permeability versus vapor size allows the permeability of various other vapors through PET to be predicted. Colorimetry showed that porous PET allowed ambient vapors to diffuse into the encapsulate, and the entire paper within the encapsulate was affected, not only the paper near the holes in the PET. [article] The Permeability of PET by Formic and Acetic Acid Vapors [texte imprimé] . - 2023 . - Pages 458-473. Langues : Anglais (eng) in Studies in conservation > Vol.68 N°3-4(2023; April-May) (2023-04-03) . - Pages 458-473 Catégories : Acide acétique Conservation et restauration -- Appareils et matériel Encapsulation (chimie) Formique, Acide Papier -- Conservation et restauration -- Recherche Polyéthylène térephtalate -- Perméabilité Revêtement en plastique -- Perméabilité Vapeur, Technique de la Index. décimale : 7.025 Dommages. Conservation. Protection Résumé : ABSTRACT The permeability of biaxially oriented polyethylene terephthalate, PET, to vapors from 5%, 30%, and 100% formic acid solutions as well as the vapor from a 30% acetic acid solution was measured by gravimetric analysis in order to determine the transmission rate of the vapors through PET folders and enclosures made from Mylar™ and similar materials, and ultimately understand the microenvironment that is created inside an encapsulate. The data shows that the permeation of formic acid vapor is at least two orders of magnitude slower than the permeation of water vapor. Measurements of the permeation of 30% acetic acid vapor through PET seemed to be due to the permeation of the water only, and the permeation of the acetic acid, if it occurred, occurred too slowly to be measured. The size of the diffusing molecule determines the permeation. Since the permeability decreases as the size of the diffusing vapor molecule increases, a plot of permeability versus vapor size allows the permeability of various other vapors through PET to be predicted. Colorimetry showed that porous PET allowed ambient vapors to diffuse into the encapsulate, and the entire paper within the encapsulate was affected, not only the paper near the holes in the PET.

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