You asked: "Can you please give me some information regarding sizing for canvas. Is pva size really better than rabbit skin glue? Which is the betterfor permenance and longevity?

Thanks."

Recent scientific testing that I'm aware of has brought to light several important facts about rabbitskin glue, aka hide glue, that indicate fairly conclusively that it is not the ideal material for sizing canvas. There are several problems with it:

1) it is hygroscopic, meaning that it absorbs moisture from the air, and reacts to changes in atmospheric moisture by shrinking or expanding, which subjects the canvas and the paint layers to changes in tension that do them no good, and indeed are harmful to the integrity of the ensemble;

2) it offers virtually no protection to the canvas fibers from the acids in linseed oi, because it is porous;

3) it loses its adhesive strength at relative humidity of 75% and up, which could cause a number of bad things to happen to a painting;

4) it's water-soluble, which could lead to it losing its grip and allowing the painting and the canvas to separate from one another in high-humidity situations or if it ever got water on it.

Neutral-pH PVA size is much better than rabbitskin glue in all of these respects. Acrylic sizing materials can also be expected to perform better than rabbitskin glue over the long term. Gamblin sells a neutral pH PVA Size, and Golden Artists' Colors has an acrylic sizing, both of which products can be reasonably expected to be more archival than rabbitskin glue, by a wide margin.

I hope this helps. I suggest asking museum conservators and conservation scientists about this, if you have any doubts about what I've told you.

Virgil Elliott