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Q. I’ve tried some old watercolor paper that absorbs water in a splotchy manner, like a paper towel, and I guess the size has degraded. Since I prefer the paper to hold paint on the surface longer, can I apply a gelatin size to restore this quality? Also, what’s the best way to store unwrapped paper?
Mary Merz
Redford, MI

A. Frankly, unless your paper has been subjected to a water bath, mold growth, insect damage, creasing or excessive surface rubbing, its sizing layer probably hasn’t degraded. It’s more likely that the paper wasn’t sized enough for your particular style of painting or that it was sized poorly, resulting in an uneven coating and therefore uneven absorption. If you’re ambitious, it’s possible to apply additional sizing yourself, and it’s also possible, although trickier, to even out an uneven application.

First a bit of explanation. Sizing is the application of a material designed to influence the paper’s handling properties. Typically applied by the manufacturer, sizing can reduce the amount of liquid the paper will absorb, give it additional stiffness or modify its texture, among other things. An example of heavily sized paper would be waxed paper, which is nearly impermeable, while at the other extreme you’d find blotter paper, which is unsized to absorb the maximum amount of water. Most watercolor papers are somewhere in between these two, though closer to the high absorbency of the unsized paper.

Gelatin is a commonly used sizing material that you could use to restore your paper. In fact, even food-grade gelatin could be used for such a purpose, as its edibility requires it to be of a certain purity. The gelatin available in the grocery store, however, tends to be sold in small amounts and at a relatively high price; technical-grade gelatin can be bought more economically through laboratory or chemical suppliers. When used as a size the concentrations of gelatin in water are traditionally quite low,

1 percent or less. Soak the gelatin first in a small amount of cold water until it looks like jelly, then add the rest of the water and heat it over low heat in a double boiler until the gelatin is completely dissolved. The sizing should be applied as a warm solution.

Gelatin sizing can be applied using a soft brush so that you don’t rough up the paper, and a fairly wide one to help ensure an even application. Spray applicators can also be used. But neither method is likely to make the sizing soak through to the other side of the paper, so make sure you remember which side you’ve sized when you begin your artwork. (The penetration of the size may be increased, however, by initially wetting the paper with a spray bottle.) With each additional coat of sizing, you’ll gradually increase both the gloss and the stiffness of the paper while reducing its absorptive nature.

To apply gelatin size locally, it helps to lightly wet your paper first and watch to see where the water is absorbed the quickest. Then apply the size to these areas with a fan-shaped blending brush to smooth the transition between the areas you’re working on and the areas that are already sized as you like.

There are other methods of sizing paper, such as immersion baths, but unless you want to become a papermaker the effort may outweigh the practicality. Examine the papers in your collection that you enjoy working on and spend some time handling them. Are they stiff, soft, glossy, heavy, textured or smooth? All of these qualities affect the rate at which the paper absorbs moisture, and you can use them to help identify the papers that give you the working characteristics you enjoy. When storing paper, keep it flat to prevent buckling, keep it covered to avoid light damage and the accumulation of dust and dirt, and keep it in an environment of stable temperature and relative humidity, one in which you yourself would be comfortable.

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