Take a fresh, mature cap and lay it on a clean piece of paper or ideally glass (to avoid paper fibres). Cover it with an upturned glass to stop it drying out; it may also be necessary to moisten the cap with a drop of water. Left overnight, or possibly longer, you should get a good print. Scrape the spores together with a razor blade to see the colour more easily. Spore droppers (Basidiomycetes) will make a print below the cap; spore shooters (Ascomycetes) will make a halo around the cap. The letters A to H used in the Russula and Lactarius text refer to the Crawshay (1930) colour code. They can be briefly summed up as: A = pure white; B = very, very pale cream; C = very pale cream; D = pale cream; E = yellowish-cream;; F = yellow-cream; G = pastel-yellow; H = yellow-ochre.