When is size not a dimension is the art version of the riddle “When is a door not a door?”
When we’re talking about paper, size does mean how big a sheet of paper is, but also what stops a sheet of paper reacting like paper towel when you add paint to it. It’s what makes paint sit “on” the surface to some extent rather than immediately soaking in and spreading. Most Western paper is internally sized, meaning it’s mixed in during the making of the paper, rather than externally sized (“painted on top”) or unsized.
Manufacturers use the terms “watercolour” / “acrylic” / “mixed media” / “drawing” paper to help guide us amidst the overwhelming array of choices. Typically:
- Drawing paper is very smooth, allowing for fine detail, and usually a lighter weight.
- Acrylic or oil painting paper is sometimes textured like canvas, sometimes smooth, and sometimes already primed with gesso.
- Watercolour paper has three finishes and comes in the biggest range of weights
— hot pressed, smooth
— not = not hot pressed; slight texture
— rough = bumpy
- Mixed media paper is typically slightly textured and a little heavier so will take some wet but not too much.
- Pastel paper has a textured surface, sometimes a sandpaper-like surface, to help hold pastel.
But just because it’s sold as “watercolour paper” doesn’t mean “thou shalt not adulterate this sheet of paper with acrylics, it’s made for watercolour and nothing but watercolour”. We can use any medium on any paper, though the results obviously depend on the surface of the paper and its weight (thickness), i.e. the characteristics of that individual sheet
You can draw on watercolour paper, you can use watercolour on drawing paper; you can use acrylic and oil paint on watercolour paper; you can use water on pastel paper to turn the pastel into paint. But you cannot expect thin paper to handle paint in the same way thick paper does. You can’t expect pencil to behave on a textured paper in the same way as it does on smooth paper.
You don’t need to gesso (use primer) paper to use acrylic on it, you can use it as is, with thick or thin paint. Adding gesso seals and changes the surface and gives a different effect to plain paper. A layer of not-too dilute acrylic on paper or acrylic medium seals the surface too, stopping it giving watercoloury effects. Gessoing paper before using oil paint stops the oil leaching out into the fibres.
If a painting dries buckled, you can flatten it by spraying the reverse to dampen the sheey and letting it dry between boards.
There isn’t a right or wrong side to most paper as it’s internally sized, but there is a difference to the surface of each side, sometimes minimal, sometimes obvious.
If the paper you’re using is balling up and tearing, switch to a thicker paper or use less liquid as that’s the surface of the paper being damaged. Heavier weight paper as it takes more working and buckles less, and dries less quickly than thin as the core retains moisture.
Thicker paper may be more expensive but you can usually paint on both sides so you get two goes with it. If you’re using watercolour as you even can put it under a tap and wash the paint off; while it won’t be as good as new and you can damage the surface if you’re aggressive, it’s good for experimenting.