How the positive is achieved?
Normal processing for Zebra Dry Plates results in a black negative but since with Zebra Tintypes emulsion is coated on black surface a special developer mixture is needed. Your goal is to make the negative white and you can achieve that by adding Ammonium Thiocyanate to the standard zebra developer (Kodak HC-110). Exact recipe goes like this:
- Mix 4ml of Kodak HC-110 into 300ml of water and then add in 3g of Ammonium Thiocyanate
More info on how to use these Dry Plate Tintypes can be found HERE