Opalines, Opaltypes, Opalotypes

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In progress: Seeking additional comments and images to develop this section

Photographic Materials Conservation Catalog
Photographic Processes
Date: Initiated January 2012
Contributors: Luisa Casella

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.

Opalines, Opaltypes, Opalotypes

Cased opaltype. Image: L. Casella
Back of broken opaltype. Image: L. Casella

The opaltype is a positive photographic image on milk glass commonly with applied color.
Historical Facts
Invented/ Patented: Joseph Glover and John Bold the Younger in 1857, BP No. 501. The patent covered the use of "Enameled glass, minerals or other suitable substances" that were washed first in fluoric acid to etch the surface and prepare it receive "the collodion or other sensitive substance", and exposed through a negative. They described how the finished image could be tinted with "water colors, oil colors, dry colors and varnish colors" (Whitman, 2007).
Main Period of Use: 1860 to 1940s (Whitman, 2007). According to Whitman (2007, pp.26) "The term opaltype became common for the process in mid 1860, although some variations in the process and nomenclature were introduced. In 1864, the British Journal of Photography reported experiments by Frederick Augustus Wenderoth, which involved the application of albumen chloride binder to ground pot-opal glass. Wenderoth called his process the Toovytype. The same article also mentions a William Helsby and his collodion iodide variant called, the Helioartistotypia, patented in 1865xlix (BP No. 12)."

Identification Characteristics
Image layer: Albumen, collodion or carbon transfer with applied color (described in patents as "water colors, oil colors, dry colors and varnish colors"
Color: Image layer is monochrome with applied color
Support: Milk glass

Process Overview
The process described in the patent is that a support - "enameled glass, minerals or other suitable mineral substances" - were washed with fluoric acid to etch the surface and prepare to receive the light sensitive layer (could be collodion, albumen or carbon transfer). Other variations of the process included grinding the surface with fine emery powder or applying a matte varnish. The plate was exposed through a negative, process and the color was applied. Opaltypes are often housed in brass frames.

Conservation and Treatment (See also Preservation of Glass in Photographic Materials)

  • Broken glass supports may be repaired with 30-40% Paraloid B-72 in acetone¬†: ethanol ( 90% acetone: 10¬†% ethanol)
  • Whitman describes consolidating flaking gelatin emulsion with 5% Paraloid B-72 in toluene (Whitman, 2007. pp.84)

Housing and Storage Opaltype housing and storage should follow with guidelines for glass supported photographs.
Emergency Recovery


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