The biggest difference between soft pastels and chalk pastels comes down to materials and quality. “Soft pastels are normally composed of small amounts of chalk or clay, water, dry pigment, and binder,” says Colletta. She explains that this type of pastel can help in creating smeared lines, smooth effects, and generating extremely bright colors. On the other hand, chalk pastels are made out of inexpensive and low-quality pigments that can fade over time, Colletta adds.