Sennelier Anti-Fusant (Stop Flow)

Discontinued by the manufacture. Check out this anti-fusant from H. Dupont!

Call it what you will, it is painted onto the silk (and dried) before the paint or dye, which it then keeps from spreading when it touches the silk. The dye stays put where you want it instead of wicking all over the place. Allows for freehand painting without Gutta or other resists to "fence" the dye. Think of it as a starch, like sizing to prep the canvas with. It washes out with water in the end. This is the only one that can also be used with flowable paints like Dynaflow and Setacolor. Clear liquid in a black bottle. 

Clear liquid in a black 3.5 oz bottle.