Check out Leanne Holt - Lost Gutta tutorial on Silk Artist blog.
I just stumbled across a great blogpost with fantastic tips on silk painting. Step by step it tells you how to create a painting on a scarf without the white gutta lines.
I used this technique last year, to create hand painted 'Autumn' silk scarf.
It was really time - consuming. You have to use delicate, light silk to ensure that the gutta will work when you apply it on the first layer of paint. If you use to heavy silk, the gutta will not work and there will be 'bleeding'.