I would recommend a 5% coat and then two 7% coats. Harden the 5% coat with
about a quarter of one percentage point solution of chrome alum ; I use
a couple of grains in 5 ml of the mix water for the 5 % gel which i then
stir in ( this to most people is heresy but it works).
Terry King
PS I now have a note on how Missonne did it which I will post to the list.