Editing Quickstartguide:Litho (section)

== Etching the stone ==
* prepare the etching fluid. This is a mixture of gum Arabic with nitric acid. If you are not sure how to do this ask one of the staff. Nitric acid is dangerous!
* use cotton wool to apply talcum powder over the image.
* pour the mixture of gum Arabic with nitric acid on a white part of the stone and use a damp sponge to move it over the image. Keep moving this around for a minute or two. Then thinner the layer of gum as much as possible.
* wait at least 12 hours
=== mixture ===
* the ratio of the mix depends on the the image 
* use 25 drops nitric acid in one once gom for a drawing 
* 10 grams gom / 8 drops nitric acid