A set of 10 black aluminium plates in 13×18 см (5×7″) for the wet plate process. Exact size 128 × 178 мм, 0.6 mm thick: black on the front, bare aluminium on the back.
What it is for
This is the support for tintype — the branch of wet plate where the image lives directly on metal. The black coating is not decorative: a collodion image is negative by nature and reads as a positive precisely because there is black behind it. Aluminium instead of the historic iron sheet does not rust, weighs less and is easier to handle.
How to dilute it
Storage
Sealed concentrate keeps well but dislikes air: the emptier the bottle, the faster it oxidises. Decant the remainder into a smaller bottle, or displace the air — that is what gets a concentrate to its last measure.
How it compares
The alternative is glass plates for ambrotype, where the image is transparent and backed with black. Metal is tougher; glass gives a different depth. For a first attempt aluminium is the practical choice — harder to break.
