Arches watercolor blocks are pretty much the gold standard for serious watercolor artists. This 9x12 inch cold press block contains 20 sheets of genuine 100% cotton paper that's acid-free and naturally white. The 140lb/300g weight is perfect - heavy enough to handle plenty of water without buckling, but not so thick that it feels like cardboard. The cold press texture has just the right amount of tooth to hold pigment beautifully while allowing for both detailed work and washes. Because it's made on a cylinder-mold machine with natural cotton fibers, the paper has incredible strength and durability, even when you're doing multiple layers or lifting color. The gelatin sizing means colors stay vibrant and don't sink into the paper too quickly. The blocks are glued on all four sides, which keeps the paper perfectly flat while you work - no more stretching or taping down individual sheets! When you're finished with a painting, just slide a knife between the sheets to release it. It works wonderfully with watercolors, but also handles gouache, acrylics, and airbrushing really well. For artists who want professional results without the hassle of preparing paper, these blocks are absolutely worth the investment. The quality difference compared to student-grade papers is immediately noticeable in how the paint behaves on the surface.