Printing on Metal
Coating metals has many surprise challenges and it has taken quite some time to develop a working process. Being used to working with paper, I found myself in a completely foreign world. Thin films of liquids on metals behave very strangely and there is much to learn on how the two interact.
I found myself confronted with one hurdle after another. Nonetheless I continued on, finding solutions to each one until I was able to produce the work I envisioned. It is a time consuming process but that is common in the arts.
I hand-cut metal plates from sheet stock and spend time hammering and finishing the surface and edges until I obtain an interesting texture. The metal is then meticulously cleaned in preparation for a thin film glass coating. This coating is applied and baked on in an oven and provides long-term protection from tarnish.
I mix up a gelatin emulsion containing a light sensitizer and transparent lightfast pigments. I apply this with any one of several brushes. I then overlay a negative and expose the plate to a UV light source. The plate is then developed in water sometimes with the aid of a brush. Light-exposed emulsion remains on the plate while unexposed areas wash off. Finally, the plate is rinsed in distilled water and a top coat of non-yellowing acrylic lacquer is applied.
Protection from Tarnish and Corrosion
Glass is much more impervious to air contaminants than organic coatings such as acrylic lacquer. When baked onto metal and overlaid with an organic coating however, the protection is amplified further. The glass acts as an excellent barrier for gases that will tarnish metals such as copper, while the organic coating resists contamination from salts. The effect is to greatly increase the metals resistance to tarnishing over time. I ran a number of tests to see what improvement there would be and found that very conservatively, these metal plates should have a longevity of many decades. These were accelerated tests however and that is why I use a very conservative estimate. There is really no way to 100% guarantee this until that time has passed although the inkjet industry seems to ignore this fact in their ink longevity estimates also based on accelerated testing.
I use a number of other processes for my paper prints. More recently I have been working with Argyrotypes and have actively worked with Cyanotypes, Gum bichromate, Casein bichromate, and Ferric-gum. I won’t go into the details of those at this time.