I have been doing a lot of experimenting with gum arabic and watercolor on paper. I started doing it when I had some fun scraping out acrylic paint with white vinyl erasers. This didn’t work well with watercolor, however, I found that using gum arabic and credit card plastic as scraping tools DID work.
Gum arabic is the glue already in watercolor. It can be:
1- applied directly to the paper (spritz paper first) and allowed to dry, then painted on.
2 – applied and painted on while still wet.
3 – mixed with watercolor, with or without 1 & 2 above.
Any of these measures allows for scrape-outs, lift-outs and more brilliant color, because the pigment sits ON the surface vs soaking in as usual.
The % mixed with water matters. I found that 25-50% solution works best without becoming glossy or cracking (those are the downsides.)
It’s not for everyone and requires a lot of experimenting, but I find it fun and it extends what you can do with watercolor.