Ceramic - Pottery Dictionary

by Susan Mussi




Photo Ceramic is the name used to refers to the process of applying photos onto ceramics. The first tests were carried out in France by Lafon de Camarsac (1821-1905), starting in 1851. Their novelty consisted in finding the way to produce a coat of ceramic colors which when vitrified became a permanent image. It was made to use with jewelry, watches and portraits replacing “painting on enamel”, which was a very complex method as the work had to be perfect and very small in size. At this time they also began using it in graveyards as it was particularly durable in adverse weather conditions and over time. Mathieu Deroche, Lafon de Camarsac and Guyot were the best known photo ceramists during this era, capable of creating photographic portraits with artistic dimensions, due to their training as miniature portrait painters on enamel.

The two oldest and most traditional methods in photo ceramics date from this period.
1) The process of using direct gum bichromate (dipped finish): this procedure is applied onto bisque or glazed pottery. A photosensitive emulsion is prepared with 2 parts of ammonium dichromate or potassium, 2 parts of colloid (Arabic gum or polyvinyl alcohol, egg, gelatin, or sugar) 1 part of distilled water, 1 part of ceramic colorant (pigment or oxides) 1 part of flux. Once the ceramic surface has been emulsified it is exposed to UV light (sunlight or lamp) with a negative film in direct contact with the surface. The heat stroke lasts approximately 15 to 20 minutes, depending on the strength of the light or time of the year if it is the sun. Then the image is developed by using water tp dampen the parts of the emulsion that were not insolubilized by light. This causes positive images to remain in the designs in the parts which remain fixed and insoluble to light.

2) The traditional process of indirect gum bichromate: this procedure is prepared on glass and then moved to the ceramic surface, which is why it is called indirect. A photosensitive emulsion is prepared with 2 parts of sugar, 1 part of Arabic gum, 1 of dextrin and 1 part of ammonium or potassium dichromate. The elements are put together as powder and then 6 parts of distilled water are added. It is then placed on a glass and when dry, it is insolated by contact with a positive film. Insolation with UV light (sun or lamp) is from 2 to 3 minutes. The emulsion will be sticky in the parts where the light does not touch and dried and attached where it does. As you work with a positive image, which is sticky (and it is where the image that is latent is produced) you carefully pass a ceramic color in the form of powder over it with a brush or your finger. This stickiness adheres to the color, which is a powder and the images appear with all its shades and half-tones. Finally a layer of collodiom is painted over it and when dry, it is put into water which loosens it allowing it to be peeled off the glass and moved onto a ceramic surface.

Two important issues are worth mentioning:
• The dichromate or ammonium or potassium dichromate is highly toxic and should be handled carefully. Do not inhale, eat or touch it and always wear gloves.
• These two procedures described are only two of the most ancient processes used, but there were many other methods with dichromates and ferric salts.

By 1960 Kodak produced a procedure of photo-sensitive resins called Cermifax which was marketed for several years with different names like Decorem or Picceramic.

In recent years digital technology has produced a system of digital photo ceramic glaze transfers that can be vitrified. The images from the computer are sent to a laser printer suitable for ceramic colors (toner ceramic) and printed on a paper for transfers and then applied to glazed ceramic. Basically the ceramic colors (mixtures of pigments and fluxes) are ground and mixed with a hot resin. On cooling the solidified mixture is pulverized to the size of the toner particle (approx. 5-6 microns). Excellent results are obtained, since the color range is wide and the surface quality is very good. The temperature for firing is between 850° and 900° C.
Link to Author – Graciela Olio.