Estupiñán Méndez Diego, Allscher Thorsten
Bayerische Staatsbibliothek, Ludwigstraße 16, 80539 Munich, Germany.
Polymers (Basel). 2022 Feb 19;14(4):808. doi: 10.3390/polym14040808.
The identification of film support material is of utmost importance for evidence-based collection management in cultural heritage institutions, especially the identification of cellulose nitrate for fire safety reasons, as nitrate is highly flammable and deteriorates over time. Cellulose nitrate film was used by photographers and movie filmmakers from its release in the 1880s to the 1950s. Cellulose acetate, being called safety film, gradually began to replace cellulose nitrate, as it is not flammable. Despite its non-flammable properties, cellulose acetate also deteriorates in hazardous ways. Therefore, identification of cellulose nitrate and cellulose acetate in collections is imperative for preservation and risk management to collections and humans. Large photographic collections can easily contain several thousand negatives or more, so a rapid, non-invasive and reliable method is needed. Traditional identification methods, such as destructive chemical tests, are sometimes unreliable, and spectroscopic analyses are normally time-consuming. To overcome these issues, rapid material characterization was performed in transflection mode with a Fourier-transform infrared (FTIR) spectrometer equipped with an external reflectance module and an additional aluminum-foil reflector. With this newly developed method, the support material (cellulose nitrate, cellulose acetate and polyester) of about 99.8% of all films can be determined within two seconds of measuring time, without any further spectral processing. Very distinctive spectral patterns are obtained with this new method, regardless of which side of the film is being analyzed. A simple visual inspection of the raw spectrum is usually sufficient to determine the film support identity. A detailed comparison of the various FTIR techniques shows the advantages of the transflection measurement for the material characterization of film support layers. This newly developed method enables the non-invasive, rapid and unambiguous material identification of even large film collections in a short time.
对于文化遗产机构基于证据的藏品管理而言，确定胶片支撑材料至关重要，尤其是出于消防安全考虑识别硝酸纤维素，因为硝酸盐高度易燃且会随时间推移而变质。从19世纪80年代问世到20世纪50年代，摄影师和电影制片人都使用硝酸纤维素胶片。醋酸纤维素被称为安全胶片，由于其不可燃，逐渐开始取代硝酸纤维素。尽管醋酸纤维素具有不可燃特性，但它也会以有害方式变质。因此，识别藏品中的硝酸纤维素和醋酸纤维素对于藏品及人员的保存和风险管理至关重要。大型摄影藏品很容易包含数千张或更多底片，所以需要一种快速、非侵入性且可靠的方法。传统的识别方法，如破坏性化学测试，有时并不可靠，而光谱分析通常耗时较长。为克服这些问题，使用配备外部反射模块和附加铝箔反射器的傅里叶变换红外（FTIR）光谱仪，以透反射模式进行快速材料表征。采用这种新开发的方法，在两秒测量时间内就能确定约99.8%的所有胶片的支撑材料（硝酸纤维素、醋酸纤维素和聚酯），无需任何进一步的光谱处理。无论分析胶片的哪一面，用这种新方法都能获得非常独特的光谱模式。通常只需对原始光谱进行简单目视检查就能确定胶片支撑材料的身份。对各种FTIR技术的详细比较显示了透反射测量在胶片支撑层材料表征方面的优势。这种新开发的方法能够在短时间内对甚至大型胶片藏品进行非侵入性、快速且明确的材料识别。
