If watercolour paper has always been a bit of a mystery, then join us to learn all the basics about watercolour papers to help you make the best decisions for your painting needs. We'll cover each of the relevant attributes to help make sense of watercolour substrates and help you to make sure that you are buying and using the best product.
Watercolour paper is made up of cotton, cellulose (tree or plant fibre), or a combination of both. Cotton papers are the highest quality and the most archival since cotton does not contain lignin. Cellulose is used for mid grade or student quality papers. The lignin in plant fibres tends to degrade over time and acidify, potentially causing yellowing. As a preventative measure non-cotton based papers are buffered with a base (usually calcium carbonate) to neutralize acidity so they can be considered acid-free.
There are three ways of making watercolour paper.
Handmade - self explanatory and the highest quality. Prized for its rough and irregular tooth (surface texture)
Mold-made - closely resembles handmade due to the random arrangement of the fibres, but is made by a combination of human hands and machine, generally good quality, good affordability, and very durable.
Machine made – made in high volume machines so the price is good, but often has a very regular waffle-like texture and poor absorbency.
The surface texture of art papers are often more rough than your standard copy paper. This texture is described as tooth . There are three surfaces that watercolour paper is available in.
Cold pressed - the most popular surface for watercolour and mixed media. It has a slight tooth which absorbs paint and wet media well and is easily workable. This paper is also great for water-soluble pencils, pastels, charcoal, inks, drawing media and mixed media.
Rough - has a distinctly deep, tooth, porous surface as fibres have been allowed to air dry without any smoothing. This finish is ideal for bold expressionistic work and textured subjects like landscapes, but not great for fine detail.
Hot press - paper is basically steamed and ironed down making a paper that is very, very slow to absorb. Hot pressed paper is easy to identify by sight or by touch as it is it extremely smooth and almost entirely toothless. This paper is excellent for detailed paintings and pen and ink.
The weight of any paper, including watercolour, is a term to denote its thickness, and is expressed most often in North America in pounds, but in grams per square meter everywhere else.
Poundage is found by weighing a ream of paper (usually 500 sheets) of a determined size. For example, if a ream of 500 sheets measured at 22x30” will weigh 300lb, making it a 300lb paper. The higher the number the thicker and stiffer the paper is.
Its important to be aware that the calculation for poundage is not standardized across the industry, so If you were to feel the weight of a 100 lb sheet from one paper mill and a 100 lb sheet from another mill, they will very likely feel like different weights (because they probably are). Since the methods of determining poundage varies from mill to mill, the measurement is variable and should be viewed as more of a guideline than a fact.
Metric paper weight is always exact. The metric measurement is very simple: the paper mill weighs a single sheet (1 m square) in grams and there you have the metric weight.
Grams per square meter is expressed in any of the following ways...
There are three standard weights for watercolour paper: 90lb, 140lb, and 300lb.
The 90lb and 140lb can buckle when wet, making it necessary to pre-stretch the paper. The 300lb will accept more water and is less likely to buckle, withstands colour lifting, reworking and general handling a lot better.
Sizing is an additive in watercolour paper that serves a couple purposes; sizing slows the absorbtion of moisture, thereby allowing the colours painted onto it to become richer rather than just soaking into the paper. Sizing also is the main factor in preventing buckling (warping) of paper when it is moistened. The addition of sizing helps the fibres to shrink back into place as they dry, enabling the paper to become flat again (just like wallpaper sizing tightens wallpaper so it flattens as it dries).
Sizing can be internal, external or both. Internally sized paper has the additive mixed in throughout the fibres and is generally found in machine made paper. Externally sized paper has the additive added after the fact and is generally found in hand made paper. Using a paper that is both internally and externally sized will allow for more reworking while still keeping the colours rich. Do not soak paper that is only surfaced sized as one of our customers recently discovered. Externally sized paper will disintegrate when submerged in water.
There are generally several ways that watercolour paper is sold. Pads, blocks, boards and sheets.
Pads - Just like a normal pad of paper glued on one edge to keep the papers together. These are available in a variety of sizes. papers are to be removed form the pad and stretched before painting.
Blocks - These are like a pad, but instead glued on all four edges to eliminate the need for stretching regardless of the weight. Great for traveling and plein air painting as they are essentially pre-stretched and ready to painted on as-is. Available in a variety of sizes.
Boards - This are sold as a single sheet of 90lb or 140lb watercolour paper that has been laminated to a rigid backing board; either an 8ply illustration board or a 1/8" masonite board. Available in a variety of sizes.
Sheets - Large format papers sold individually, often in 22x30" sheets or larger. Sheets are available in a variety of sizes, weights, and finishes.
There you have it, watercolour paper in a nutshell! Next time you go shopping for waterclour paper you should be able to make great decisions and start your masterpiece off on the right substrate.