Sponge brushes are a cheap alternative to paint brushes. You can make them in different sizes and shapes to meet different painting needs. I make four categories of brushes, pointed brushes, round tip brushes, flat brushes, and texture brushes.
When held vertically, pointed brushes make variable width lines by raising or lowering the brush. Round tip brushes can smudge already applied paints, or help fill in areas. The flat brushes have a marking edge that is a straight line and can leave calligraphic marks. Texture brushes have high and low areas that print different patterns.
The materials used are mattress foam, bamboo kitchen skewers, and a dab of glue to keep the foam on the stick. For the glue, I used a liquid silicone glue often found in fabric or craft stores. Other water-resistant glues will also work.
Step 1: Preparing the Basic Brush
Take a big knife (or machete) and slice the mattress foam into slabs. Use scissors to cut the slabs into strips.
Poke a hole in the foam pieces with a sharp tool (ice pick) and then insert the bamboo skewer. Try not to have the wood extend out the top of the brush. Alternatively, if you don't mind having the sharp tip of the skewer inside the brush head, just push the sharp end of the stick directly into the foam.
To keep the foam on the stick run a little of the silicone glue around the stick where it meets the foam. There is no need to have glue on the whole embedded part of the stick. A
Step 2: Brush Types
Use precise scissors to shape the foam brush heads. Use pliers, or tweezers to pluck chunks of foam from the surface to make the texture brushes.
The flat brushes have a tip that is like a wedge. The marking tip is a straight line. Larger foam flat brushes can be bought in paint stores.
Pointed brushes, held vertically, can make a narrow or wide line depending on downward pressure.
The rounded brushes can be used dry to smudge already applied paint, or to apply broad areas of paint or ink.
The texture brushes have had their surface butchered by plucking out pieces of foam with pliers or tweezers.