Salted Paper, Blanquart-Evrard process

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Photographic Materials Conservation Catalog
Photographic Processes
Date: Initiated June 2012
Contributor: Amanda Maloney Stephanie Watkins

The Photographic Materials Conservation Catalog is created and maintained by the Photographic Materials Group of the American Institute for Conservation for the convenience of the membership. The treatments, methods, or techniques described herein are provided for informational purposes. The reader assumes responsibility for any application results or interpretation of information.

Salted Paper/ Waxed Paper Negatives

Much of this information was presented by Jiuan-Jiuan Chen at the 2011 FAIC Workshop on 19th Century Negatives.

Historical Facts
Invented: The first viable paper negative process was developed by William Henry Fox Talbot in the late 1830s. In 1847 Louis-Désiré Blanquart-Evrard developed a simplified version of Talbot’s formula and published it in France. Gustave Le Gray further improved the process by adding a waxing step, which enhanced the clarity and transparency, and published his method for creating waxed paper negatives in 1851.
Patented: The first salt-print negative process was patented by William Henry Fox Talbot in England 1841 and called a calotype.
Historic Practioners: Talbot, Hill and Adamson, Louis-Désiré Blanquart-Evrard, Gustave Le Gray, Édouard Baldus, Heri Le Secq,
Contemporary Practioners:

Identification Characteristics
Image layer: The image is formed by silver deposited directly in the paper support.
Color: Range from warm brown to cool gray tones.
Support: paper
Analysis: 
(Non-destructive) XRF can be used to identify the silver image and also detect sulfur if the image has been fixed in sodium thiosulfate. (Destructive) GC-MS may be used to identify coating materials.

Basic Process Overview

Material Properties of Beeswax
Composition: Approximately 67% esters, 14 % hydrocarbons, 12% free acids, 1% alcohols, and 6% other materials.
Solubility: Soluble in acetone, toluene, carbon tetrachloride, chlorinated hydrocarbons, chloroform, ether, turpentine, white spirits, and the following if used hot: benzene, ethyl alcohol, and amyl alcohol; partially soluble in ethyl alcohol.
Note that beeswax is hydrophobic but it is permeable to water (that’s why waxed paper negatives can be humidified and flattened), especially if it has been subject to certain forms of deterioration.
Thermal Properties: In general beeswax is brittle under 18 °C (65°F), plastic above 30-35 °C (85-95 °F) and will melt at 60-70 °C (140-158 °F). Interestingly, the thermal properties of the wax can vary quite substantially depending on the type of honeybee that produced it (Buchwald et al. 2008, 121-127). Irreversible color change if heated beyond 85 °C (185°F)

Types of Deterioration
Corrosion: It is a slightly acidic material and may cause corrosion of Fe, Cu, Zn, Al, which in turn will discolor the wax.
Saponification: If exposed to water and/or alkalis the ester groups can undergo saponification, thus making it more prone to water absorption and biological attack.
Biodeterioration: Fungal attack will cause loss of fatty acids, alcohols and smaller ester components, which are plasticizers. Thus resulting in shrinkage, embrittlement and cracking of the wax.
Bloom: Migration of some of its low-melting and plastic components (plasticizers) to the surface resulting in a whitish haze. This is caused by fluctuating temperatures that encourage a rearrangement in the crystalline structure of the wax.
Physical damage: Usually caused by poor handling and can consist of small white crescent creases, tears, and losses.

Housing and Storage Considerations
Temperature: A stable temperature between 18 and 30°C is necessary to avoid embrittlement, melting, or developing a bloom. Cold storage is not advisable unless rigorous handling and acclimatization procedures are in place.
Relative Humidity: Between 30% and 50% to avoid saponification and biodeterioration.
Housing: There are a variety of good choices of paper and plastic materials that have passed the PAT and are suitable for housing waxed paper negatives. One must consider all factors (research, access, preservation, exhibition, art in transit) and balance the pros and cons for a specific collection.

Emergency Recovery Tips

Helpful Treatment Techniques, Things to Know, and CAUTIONS!
For white opaque creases or bloom: Heat or solvents can be used to reform the wax. Any one solvent will not dissolve all components of the wax, so heat is usually the preferred method. One must be able to regulate temperature with a rheostat and isolate the area being treated. This may cause the treated areas to have a slight saturated look if the paper negative has an overall bloom—which most waxed paper negative do.
For tears or losses: Adhesives used: methylcellulose, wheat starch paste, Klucel G in water or ethanol. 8% Klucel G in ethanol, is preferred because it should be easily reversible and is the least likely to cause any planar deformations (Purreux 2008).
Repair papers: toned Japanese papers.
Tip: To maintain the transparency of the mended area individual fibers can be teased out from the Japanese paper and used to make a discrete mend across the tear. This is a great method to preserve both its quality as a negative and as an object.
Fill papers: Chose a PAT approved paper that is an appropriate thickness. It can be waxed to give it added transparency and toned. Tests performed by Hanako Murata show that wax does not increase the thickness of the paper, but toning will add a couple of mils.

Resources
Conservation, Negatives Albright, G., J-J. Chen, and K. Jennings. 2003. Treatment options for paper negatives. Topics in Photographic Preservation 10: 19 – 28.

S. Berselli. 1996. La negativita del negative: riflessioni sulla conservazione ed il restauro dei Negative. International Conference on the Conservation and Restoration of Archive and Library Materials, 22-29 April: 709-720.

Buchwald, R., M. D. Breed, and A. R. Greenberg. 2008. The thermal properties of beeswaxes: unexpected findings. The Journal of Experimental Biology 211.

Clydesdale, A. 1994. Beeswax: a survey of the literature on its properties and behaviour. SSCR Journal (the Scottish Society for Conservation and Restoration) 5 (2).

Daffner, L. 2005. Coatings on paper negatives. In Coatings on photographs: materials, techniques, and conservation, ed C. McCabe. Washington D.C.: Photographic Materials Group American Institute for Conservation of Historic and Artistic Works. 66-77.

Jennings, K. 2003. Research into the conservation of 19th century paper negatives. Capstone research project at the Advanced Residency Program in Photograph Conservation, George Eastman House, Rochester. http://notesonphotographs.org/images/2/24/Kate_Jennings_ARP_Project_for_web.pdf

Kuznesof, P. M. Beeswax: chemical and technical assessment. Chemical and Technical Assessment 65th JECFA.

S. Bogdanov. 2011. Chapter 2: beeswax: production, properties, composition and control. In Beeswax book. http://www.bee-hexagon.net/en/protected-sid-V2F4Qm9vazIucGRm.htm (Accessed June 2011)

Beeswax Co. LLC. Beeswax facts. http://www.beeswaxco.com/beeswaxFacts.htm (Accessed June 2011)

Horie, C. V. 1997. Materials for conservation. Oxford, UK: Buterworth-Heinemann.

Mills, J. S. and R. White. 1996. “The organic chemistry of museum objects.” Oxford, UK: Buterworth-Heinemann.

Mayer, R. 1992. The artist’s handbook of materials and techniques. New York, NY: Penguin Books.

Murata, H. 2003. Paper negative project—housing. Unpublished research project on paper negatives at the Advanced Residency Program in Photograph Conservation, George Eastman House, Rochester.

Perreux, A. 2008. Conservation-restauration de trios négatifs sur papier d’Alphonse Davanne et de quatre negatives sur papier d’Henri-Vicotr Regnault appartenant à la Société française de photographie. M.A. thesis, Département des restaurateurs, Institut National du Patrimoine.

A. P. Tulloch. [1980] 1983. Beeswax: composition and analysis. Nature 308 (5914). Reprint, Bee World 61(2): 47-62.

Process and Historic Material Root, M.A. 1864. The Camera and the Pencil, History of the Heliographic Art, Philadelphia Scully, France and Osterman, 2009, Mark, "Scully and Osterman" website: http://www.collodion.org/q&a_salt.html
Contemporary Practice

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