I have known it was PVA with additives for ten years.
I started using it at Gloucester Art College as an emergency substitute for gum
arabic. I asked Henkel what it was when exposures proved to be embarrassingly
shorter than was needed with gum arabic.
I used it at workshops for the Royal and for The National Museum at Bradford and
at workshops and courses since; in effect, spreading the word. i mentioned it in
magazine articles eight years ago. I had a number of US students when I gave gum
courses at Central/St Martins.
I have always told students it was PVA but not to use pure PVA because it is
difficult to control. I thought you came to one of my Royal workshops at
Twickenham.
The best water-colour effect and the most control comes from gum arabic as it is
slower but success rates for complicated multicoatings are far lower.
Terry