In most painting media the surface is a support and the paint does the work. In watercolor it is closer to the other way round. The paper decides how far a wash spreads, how hard an edge dries, whether a color can be lifted off again, and how the whole thing looks when it is finished.
Which is why a beginner painting good pigment onto poor paper gets a poor result and concludes they cannot paint.
What watercolor paper actually is
Two things matter: what it is made of, and how it is sized.
The fiber. Better papers are made from cotton, often described as 100 percent cotton or cotton rag. Cotton fibers are long and strong, they hold up to repeated wetting, and they let you lift color off again. Cheaper papers are made from wood cellulose. They are perfectly usable for practice and they behave differently — less forgiving of scrubbing, and colors tend to sit rather than move.
The sizing. A gelatin or synthetic size is added to slow how fast the paper absorbs water. This is the property nobody explains and it governs almost everything you notice. Heavily sized paper keeps the paint sitting on the surface, so washes stay bright and edges stay controllable. Lightly sized paper drinks the paint straight in, so washes go flat and dull and you cannot move anything once it has landed.
Different manufacturers size differently, which is the real reason two sheets described identically can behave nothing alike.
The three surfaces
Hot press is smooth, pressed between heated rollers. Fine detail sits crisply on it and brushwork shows. Because there is no texture to hold the water, washes dry fast and unevenly, and the paper is unforgiving of hesitation. Good for botanical work, illustration and anything detailed; hard for large skies.
Cold press has a moderate texture and is what most people should use for most things. The tooth holds water long enough to give you time, takes a wash evenly, and is good for drybrush. If you buy one paper, buy this.
Rough has a pronounced texture. A loaded brush skips across the peaks and leaves the valleys white, which produces sparkle in a sky or on water that you cannot get any other way. It is poor for detail, because fine lines break up on the texture.
One thing worth knowing: on many papers the two sides differ, one more textured than the other. Neither is wrong; try both.
Weight, and what it means
Paper weight is given in pounds per ream or in grams per square meter, and it is a proxy for thickness. The common grades:
- 90 lb, about 190 gsm — light. Fine for sketching and practice. It will buckle when wet unless you stretch it.
- 140 lb, about 300 gsm — the standard, and the right default. It handles ordinary washes without stretching, though a very wet approach will still cockle it.
- 300 lb, about 640 gsm — heavy, closer to board. It takes anything you throw at it without stretching or buckling, and it costs a great deal more.
If you are buying one thing, buy 140 lb cold press. It is what most watercolor teaching assumes and it is widely available.
Buckling, and stretching
Paper expands when it gets wet and shrinks as it dries. On a light sheet that produces cockling — ridges and valleys across the surface — and paint pools in the low points, which is visible in the finished work.
Stretching prevents it. Soak the sheet in clean water for a few minutes, lay it on a rigid board, tape all four edges down with gummed paper tape, and let it dry completely. It dries taut and stays flat while you paint. Soaking time goes up with paper weight; a light sheet needs only a couple of minutes.
Two ways to avoid the job entirely. Use 140 lb or heavier and keep your washes reasonable. Or buy a block — a stack of sheets glued on all four edges, so the top sheet is held flat until you finish and slide it off. Blocks are the practical answer for painting outdoors.
Staining and lifting
Worth separating two things that get confused.
Transparency is about the pigment: how much light passes through it to the paper and back. It has nothing to do with the paper.
Staining is about whether a pigment sinks into the fibers and refuses to come out. A staining color cannot be lifted off with a damp brush; a non-staining one can, which is how a lot of highlights get made. Some pigments stain more than others, and heavily sized cotton paper lets you lift far more than lightly sized cellulose does.
If being able to take color back off matters to you — and it is one of the real pleasures of the medium — that is a paper decision as much as a paint one.
What regular paper does
Printer paper buckles immediately, tears when you work it wet, and absorbs the color so fast that everything dries flat and pale. Cartridge and sketching papers are better but not much.
You can use them to practice mixing and brush control, and it is worth doing precisely because it is cheap. Just do not judge your painting by what comes out.
Choosing, in one paragraph
140 lb cold press, in the largest sheet you can afford, cotton if the budget stretches to it and cellulose if it does not. Then paint on it a great deal rather than saving it for something good, because paper you are afraid to waste is paper you will not use.
Buy one sheet each of hot press and rough at some point to see what they do. The difference will teach you more about watercolor in an afternoon than a chapter of a book.
A note on our own kits
Since people find this page from our site: our paint by numbers kits are acrylic on primed cotton canvas, not watercolor on paper. Acrylic behaves in almost the opposite way to watercolor — it is opaque, it covers itself, and mistakes can be painted over rather than lifted, which is a large part of why it suits a numbered design.
If watercolor is what you want, the paper is where to spend your money, and none of it is available from us. If you would like the acrylic version, our note on choosing an acrylic paint set covers the materials, what gesso is covers priming a surface yourself, and the designs are in the full collection.
