What is the substance used in painting that like a glue you brush on and it dries so paint get area then can peel off?

The substance you're describing is called masking fluid. It's a liquid rubber-like substance that acts as a temporary barrier to paint.

Here's how it works:

* Application: You brush or apply it to the areas you want to protect.

* Drying: The fluid dries into a rubbery film that resists paint.

* Painting: You then paint over the masked areas.

* Removal: Once the paint is dry, you can peel away the dried masking fluid to reveal the protected areas.

Masking fluid is used for various purposes in painting:

* Creating sharp edges: To get clean lines between painted areas.

* Protecting delicate areas: When painting around small details or intricate designs.

* Creating special effects: For example, by masking out portions of the painting to create a "negative" effect.

It comes in different consistencies (thick or thin) and can be found in art supply stores.