Block - A watercolour block is a pad of watercolour paper that has been glued on all 4 edges. There is usually a little break in the binding, either on a corner or at the middle of one side, so that when you have finished your work it is easy to insert a palette knife just under the edge of the top sheet and slice the page away from the block; the work is then ready for framing. Watercolour blocks are practical to use as they remove the need to stretch your paper before you paint – the paper may buckle as you work on it, as it absorbs more and more of the water and paint you apply to it, but when the water evaporates, the binding on the edges is still there to ensure that the sheet will dry flat and resume its original position. Watercolour blocks are most commonly available in not and hot-pressed surfaces; not all manufacturers offer a rough block because the irregularity of the surface makes it more difficult to bind paper in this way.
Glued Pads - Glued pads are glued on one side only.
Spiral (Ring) Bound - A spiral-bound pad is great for plein air watercolourists because you are able to access a number of sheets at any one time and unlike a sketchbook, the spiral-bound pad lies completely flat when open. Sheets can be removed with ease, but will need to be trimmed at the spiral bound edge.
Sketchbook - sketchbooks are bound on one side, either with staples or stitching, making them low-cost workbooks for any artist sketching or illustrating.