Recently I have been printing cyanotypes onto wood. I use the traditional cyanotype formula for my emulsion. Before I apply the emulsion, I size the wood. While this isn’t necessary, it does provide more repeatable results, and allows for the removal of residual iron that would otherwise harm the wood. I have used gum, gelatine, starch, and Gamblin’s PVA or combinations in layers. They all produce different results.
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.
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 when attempting to apply an even and thin emulsion coating.
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 could use other alternatives especially for the aluminum as it won’t tarnish indoors but the film also gives it a durability and reduces the risk of scratching should I have to do a re-coat which happens occasionally due to dust dropping down while the emulsion dries.
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.