What is the purpose of watercolor blocks?

Watercolor blocks serve the specific purpose of holding sheets of watercolor paper together securely until the artist is ready to use them. This is particularly useful because watercolor paper is often heavier and less likely to warp when pre-stretched or glued down on a block. The edges of the block are typically adhered, allowing the artist to paint without needing to tape down the edges of the paper, which can create a cleaner and more manageable work surface. When the artist has finished the painting, the individual sheets can be easily removed without damage to the artwork.

The other concepts presented in the options do not align with the primary function of watercolor blocks. Textured surfaces for oil painting, mixing of colors, and layering paint are important aspects of the artistic process but are not the designed purpose of watercolor blocks themselves.