When painting, having the right kinds of brushes makes a world of difference. This is especially true for silk painting. Silk is a delicate fabric, and using the wrong brushes could have devastating effects. Besides that, the paints and dyes used on silk are very different from the paints used on canvas and other materials.
Experienced and frequent silk painters often have a veritable arsenal of brushes. They have rounded brushes, flat brushes, thin brushes and flat brushes. Many are dedicated to a specific brand, and they often prefer those with animal hair as opposed to synthetic bristles. The brushes they use tend to be quite expensive.
It's true that animal hair brushes offer certain advantages over synthetic ones. They have a softness that simply can't be reproduced with man-made materials. This allows them to soak up much more dye, making it easier to fill in areas large and small. It also makes them safer to use on fragile silk and silk blends.
Many professional silk painters use sumi brushes with bamboo handles and goat hair bristles, which become stiffer in the center and soak up more liquid than regular brushes. Sumi brushes have been used by Chinese silk painters for centuries.
But for beginners, it may not make sense to spend a lot of money on high-end silk painting brushes. Until you decide whether or not you want to do silk painting on a regular basis, it's probably best to use less expensive brushes. Synthetic watercolor brushes work reasonably well for silk painting. They may not hold as much paint or dye as natural ones, but they will not harm the silk. They should do fine for your first few projects.
No silk painting brush collection is complete without some foam brushes. The larger ones work very nicely for coloring in large areas, and they're especially useful when applying fixatives and primers. You can also purchase smaller ones (which look similar to eye shadow applicators or cotton swabs) that are great for applying resist and creating details with silk paint.
Foam brushes are usually very inexpensive. However, most of them must be replaced frequently. If you find them useful, it might be best to buy them in bulk.
The sizes and types of brushes used by one silk painter might be completely different from those used by another. The brushes you'll need depend largely on your preferences and the techniques you use. Just remember that there is no one brush that will do everything you need to do. In order to be successful at silk painting, you'll need at least a few different sizes of brushes, and probably a couple of different types.