Jeff gave his results for his gum tests.
Here is some of my experience with gums.
W & N gum arabic was, I thought, about 17 Baume but what's a degree between
friends. It was what I started with and it worked very well. I found that it
worked particularly well if you were intending to avoid the necessity for sizing
first, something that Demachy, who was quite good at gum printing, was not very
keen on. I found that lighter gums made for etching resists tended to soak into
the paper too easily and that this led to degradation of the highlights. This
will probably not be a problem if you size first. This gum is intended as a
lacquer for water-colours.
Le Page's fish glue. This material is so glutinous that the idea of putting my
Baume hydrometer into it does not appeal. It made perfectly good gum prints but
in its undiluted state tends to produce soft impressionistic images which leads
one to wonder if the heavier the gum the softer the image.
White gum powder mixed 500 g with 500 ml of cold water has sometimes produced a
gum akin to the W & N and sometimes to the fish glue.
Gum Royale, in lumps still with the camel dung and bits of tree, mixed g for
ml, gives a consistency similar to W & N.
Gloy. Many of us have been using Gloy with great success for so long that it is
very difficult to understand how anybody manages not to make it work. The
consistency of Gloy and the W & N gum seem to be similar. They work in the same
way too. But the Gloy is about a quarter of the price of the W & N gum arabic.
Terry King