1. Dissolve 5g of gelatine in 1 litre of distilled water. Do not heat over 60C.

  2. When the gelatine has dissolved add 0.5g of chrome alum (chromic potassium sulphate).

  3. Cool and dip racks of slides or coverslips into the solution.

  4. Drain slides and coverslips onto paper tissue.

  5. Dry overnight in a 37C incubator.