Water, paper and sizing
Ever heard of a watercolor paper surface gluing? No! Then you should read this.
All paper has glue in the pulp, otherwise the paper would not stick together. Some papers have only a little glue others are glued hard, depending on the type of paper. All good watercolor papers are, moreover, glued on the surface, sizing, it is a costly process and therefore only the expensive papers have this surface sizing,
The sizing prevents the watercolor pigment from reaching the paper fibers. The color sticks to the glue which in turn adheres to the paper, it is this sizing that enables the production of a porous and absorbent watercolor paper, since the paper is glued to the surface does not need as much glue in the pulp. more absorbent paper.
A simple watercolor paper that does not have sizing must be glued much harder in the pulp to prevent the watercolor paint from being sucked in as on a blotting paper. Such paper is difficult to paint on, some of them feel like painting on plastic.
But even if sizing is absolutely crucial for a good watercolor paper, it causes a problem. It MUST be treated before painting on it, otherwise the painting loses depth and intensity in the colors, Since no one seems to be aware of this, it is a problem.
The sizing is not evenly distributed, it is full of small air bubbles and other irregularities, these are removed by brushing the paper with water. From left to right, from top to bottom, perhaps even diagonally. In this way, the glue is evenly distributed over the paper and it becomes much better to paint on.
If you want to paint wet on wet, start painting immediately, if you want to paint on dry paper, you have to wait a few hours.
Here’s the difference
Both samples below are painted with phthalo blue, the one on the left is on Arche’s paper, on the right is Saunders Waterford. The lower part of the papers is treated with water while the upper part is completely untreated. The result is a deeper color on the treated surface and you avoid the white dots that you can see in the detail picture.