“Of all the tools you’ll use in transparent watercolor, by far the most important one is your paper. Watercolor paper must be of good quality and have a permanent whiteness.” - John Pike as quoted from his book Watercolor
Paper is indeed the most important material you’ll use in watercolor. The paper’s quality, thickness and texture all affect its performance and the picture’s final appearance. The highest quality papers are handmade or mould-made and have a 100% rag content - which means it's 100% cotton. Most others contain wood pulp that will eventually turn yellow and deteriorate with age.
I primarily use D'Arches Aquarelle, which is mouldmade at a 500 year-old mill in Lorraine, France. Other excellent mills include Fabriano Artistico from Italy, R.W.S. Cotman (the official watercolor paper of the Royal Watercolor Society), T.H. Saunders and J. Whatman - all three are milled in England.
Watercolor paper is prepared in three different textures; rough, cold and hot-pressed. Rough is coarsely textured, hot-pressed is smooth and cold-pressed is in-between. I favor rough for my landscape work where a broken-edge look is easily created with a dry brush technique.
All handmade and mould-made papers are initially rough. Cold and hot-pressed papers go through an additional step to produce their textures. Hot-pressed’s surface is achieved by running a rough sheet through two heated drums, which acts like a hot iron. The result is a very smooth surface - great for lifting techniques. For this reason, I prefer to use it for portrait painting.
Cold-pressed paper is manufactured by flattening it with cold drums - hence its name. This produces a slightly rough surface. I use cold-pressed paper for finely detailed paintings, florals, still life, landscape - or just about anything.
Paper is priced according to its size and thickness. The most popular size is imperial which is 22” x 30.” Some other sizes and their trade names include; Royal - 19” X 24," Super-Royal - 19” X 27," Elephant – 23” X 28," and Double Elephant – 26” X 40.”
Paper’s thickness is classified by how much 500 sheets weigh. Common weights are 90 lbs., 140 lbs. and 300 lbs. Paper less than 300 lbs. will buckle up when wet which can be frustrating to work on. I use the more expensive 300 lbs. paper because it doesn’t require any special preparation to prevent buckling. Also, thicker paper stays wet longer, which is useful for my wet-in-wet technique.
Although you can paint on both sides of the paper, the screen side has a slightly better finish. You can identify the screen side by locating the manufacturer’s watermark. Hold the sheet up to a light and you’ll be able to see it in the lower right hand corner of the sheet. The side that you can read the watermark is the better one.
I recommend buying watercolor blocks for classroom work and Plein air sketching. A watercolor block is 10 - 25 sheets of watercolor paper, usually 140 lbs. weight, with its four edges glued together. Watercolor blocks are convenient, but expensive.
A better alternative is to clamp or staple a sheet of paper to a piece of Gatorboard, or Homasote. Gatorboard is a lightweight ½ inch thick foam board. It comes in several sizes to accommodate a full, half and quarter size sheet of paper. Homasote is a very heavy, thick piece of cardboard that can be purchased at any hardware or lumber store. It’s sold in a 4’ x 8’ size, which can be cut smaller with a utility knife. I use four large bulldog clamps to secure the paper to the sheet and move them around as I paint to flatten any raised, wet areas of the paper.
When selecting paper, you get what you pay for so always buy the best paper you can afford. I would love to hear what kind of paper you use and what measures you take to prevent the paper from buckling.