A Few Tips on Watercolour Papers
Probably one of the most important aspects of choosing Watercolour paper is the surface texture as this will either help you or hinder you with your watercolour painting. Watercolour paper is divided into three categories according to the surface of the paper: Rough, Hot-Pressed (HP), and Cold-Pressed (NOT).
Rough watercolor paper, as you'd expect from the name has the most textured surface, or most prominent tooth. It's described as having a pebbly surface with a series of irregular rounded shapes just like a pebbled beach. When using rough paper the paint from a very watery wash tends to collect in the indentations in the paper, creating a grainy effect when the paint dries. Alternately if you dry brush lightly across the surface, you'll apply paint only to the raised parts of the paper, the paint will only touch the tops of the ridges and not in the indentations. Rough paper is generally not a good paper for painting fine detail, but it is excellent for a loose, more expressive style of painting.
HP stands for "Hot Pressed" and is the smoothest paper and is suitable for high detail work. Hot-pressed watercolour paper has a smooth surface with almost no tooth. Its smooth surface is ideal for painting fine detail and for even washes of color. HP is not an ideal surface for beginners as they sometimes have problems with the paint sliding around on the smooth surface.
Cold-pressed watercolor paper is sometimes called "NOT" (as in "not hot pressed"). It's a slightly textured paper and is the most popular as it's suitable for most types of work. Cold-pressed paper is a medium paper, in between Rough and Hot-pressed paper and having a slightly textured surface. Cold-pressed paper is the most commonly used watercolour paper as it allows for a good amount of fine detail work while also having enough texture to allow a more loose expressive style of painting.
The thickness of a sheet of watercolour paper is measured by its weight. So the greater the weight, the thicker the paper. Watercolour paper is measured in either (lb) pounds per ream or (gsm) grams per square meter. Most papers have both weights advertised as standard. There are 4 standard weights of watercolour paper, these are 90 lb (190 gsm), 140 lb (300 gsm), 260 lb (356 gsm), and 300 lb (638 gsm).
When you use a thinner paper it needs to be stretched, this is done to prevent the paper from buckling or warping when you paint on it. How thick the paper needs to be before it will start buckling does depend on how wet you tend to make the paper as you paint. The best way to decide which is the best weight of paper for your painting style is to experiment with different weights to see, but it's likely you'll find that paper with a weight of 140 lb (300 gsm) or less needs to be pre -stretched.
How to pre-stretch Watercolour paper: If you have chosen a paper of 140lb (300gsm) or less then the chances are you will need to pre-stretch your paper. The reason for pre-stretching is with the lighter weight papers when you apply water it moves and buckles, or "Cockling". This happens when the application of water when painting, will cause one side of the paper to expand slightly, the other side will remain dry and due to the sizing contained within the sheet will not expand. To counteract the papers movement on the wetted side, the paper buckles and warps. This then causes the very unsightly effect of buckling which is not ideal for the finished painting, and is also quite difficult to work with.
1. Immerse your sheet of paper either in a bath of cold water or under a tap for approximately 1 to 2 minutes, this is to allow the fibers in the paper to expand. Take care when handling your paper, ideally before you start wash your hands thoroughly and do not touch the area you intend to paint, this is because the paper is fragile when it's wet and also your finger marks will show up in your wash due to the grease on your fingers.
2. Carefully place your soaked sheet of paper flat on a board.
3. Using gummed tape, stick down all four edges of your paper, you can also staple down your paper but do not use heavy duty staplers as it will be hard to get the staples out which may result in you damaging your paper.
4. Blot any excess water from your paper, ideally use a clean sponge and leave to dry on a flat surface, a flat surface is preferred otherwise the water will drain to one edge and the paper will dry unevenly.
5. Leave your paper to dry at least for a couple of hours, but ideally over night. When your paper is completely dry it will be stretched tightly on the board and when you apply your wash the paper will not move or buckle again.
All Watercolour paper is made with a difference between the two sides, one side is usually slightly smoother and the other side has a slight hairier texture to it. There is not a right and wrong side because which you use would depend on what you require from your watercolor paper. The smoother side of a paper is better if you're painting a lot of detail, while the hairier side is better if you want to build up color by using lots of glazes.
The color of watercolor paper varies from manufacturer to manufacturer and even between the different types of paper made by the same manufacturer. Watercolour paper does not just come in white it can range from a warm, rich cream to a cold, blueish white. The difference in color tones can sometimes be easy to see, but at times it can be so slight that it is hardly evident even when you have two different sheets of watercolor paper next to one another.
One thing to consider when choosing your watercolour paper is that the different color tones of paper will affect your paintings, as basically your starting painting with a glaze, so this will have an impact on your painting. A watercolour paper with a slight cream color can make your colors appear muddy or dull. A watercolour paper with a blueish tint can give your yellows a greenish appearance. When you are buying your watercolor paper, take its color tint into consideration just as much as you would its texture and weight.