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We would advise using water washable inks at home: Caligo Safewash Inks are oil based, and don’t dry out too quickly whilst you’re working, but clean up with soap and water.
If you are brushing ink on, (on a fish for example) it might need thinning down slightly. Caligo make an oil specifically for these inks, as adding traditional oils would mean using solvents to clean up.
Rolling on might require 2 different rollers, one hard and one softer, like a sponge roller, so you can adapt to different surfaces on objects.
Applying pressure will depend on the object: sometimes hand pressure will be enough, especially on soft objects, but you could also try a rolling pin, a wooden spoon, or a traditional “baren”.
Thinner, lightweight papers will make this easier, newsprint, tissue paper, or if you’re lucky enough to have any Japanese paper to hand. Maybe you could even experiment with lightweight fabrics, such as old bedsheets or pillow cases, that could mould around the objects?
To use the prints as negatives/positives for cyanotype, there will need to be some transparency to the surface you’re printing on, so again thin paper such as tissue, layout paper or tracing paper might be suitable, but will need testing.
If you need any more information, or suppliers, please ask away!
Let us know how you get on!