Watercolour paper is a versatile surface which has a degree of absorbency that allows transparent colour to appear its most luminous. Watercolour paper is not only for use with watercolour paints – it can also be used for acrylics, gouache, pastels, pencils, graphite, charcoal, and it can also be primed for oil. With many options that are 100% cotton, it can make a durable and archival support for many different mediums. If you’re unfamiliar with any of the watercolour paper terms, click on the underlined words to read the definition.
List of Contents:
What is Watercolour Paper Made of?
Acid-free Wood Pulp
The most affordable watercolour papers, as well as those found in many watercolour sketchbooks, are made with wood pulp that has had naturally occurring acidic components, like lignin, removed. As a result, these papers resist discolouration and yellowing, but they are not as durable as cotton papers.
Cotton linters are the purest source of cellulose and their fibres are longer than in wood-free pulp, making a durable paper that can take heavy treatment. Most 100% cotton watercolour papers are made using cotton linters.
A Blend of Acid-free Wood Pulp and Cotton Linters
A percentage of cotton linters in these papers adds strength and durability, while being more affordable than 100% cotton watercolour paper.
Cotton rag papers are made with recycled cotton textiles. Cotton textiles are made using the longest fibres from the cotton plant, so cotton rags make even stronger paper than cotton linters alone. Cotton rags are mechanically beaten in such a way as to maintain this long fibre length.
Cotton and Linen Rag Blend
In addition to cotton rag, some papermakers add recycled linen cloth to their papers. Linen is derived from flax and is even stronger than cotton. Its long, thin fibres interlock with the cotton fibres, adding even more durability.
Hot pressed paper has the least textured surface, having been pressed between hot metal rollers during production. Hot pressed paper is favoured by those who like to work delicately with a lot of detail, such as botanical artists. Hot pressed paper tends to be the least absorbent of all of the textures, and watery washes can sit on the surface for a long time. Beyond watercolour painting, hot pressed watercolour paper makes an excellent support for detailed pen, ink and graphite drawing.
Cold pressed (NOT) paper is made by pressing the sheet through cold metal rollers, and it has a slight texture to it. It is the most popular watercolour paper surface to work on because it is well adapted to many painting approaches. The paint will sink a little into the dimples on the surface of the paper, but it will also be sympathetic to some more detailed work. Cold pressed paper tends to be a little more absorbent than hot pressed paper.
Rough paper is the roughest texture paper available, it is pressed between sheets of textured felt during the drying process and is not pressed between smooth rollers. The heavier texture means that granulating effects are enhanced. This paper surface is suited to bold, expressive painting techniques.
While hot pressed, NOT, and rough are used almost universally by watercolour paper manufacturers to describe the texture of their papers, the actual surface textures vary greatly between manufacturers, or even between batches (particularly with handmade papers).
Because watercolour paint is transparent the colour of the paper, even different shades of white, will affect everything on top of it in both the painted and unpainted areas. The colour of 100% cotton watercolour papers vary depending on whether it is tub sized or not (external gelatine sizing will impart a slight brownish tinge), the purity of the water used in production, and the raw materials used for manufacture. Many 100% cotton papers are an off-white colour which is often referred to as ‘traditional’ white. Some ranges have a separate line of ‘extra-white’ or ‘high-white’ alongside their traditional white papers.
Optical brightening agents, or OBAs, can be added to the pulp during production to make the paper whiter and brighter. These brightening agents are prone to deteriorating over time, which can cause a colour shift in the artwork as the paper fades to off-white. Because of this, makers of archival standard watercolour papers avoid the use of optical brightening agents and add a lightfast white pigment, like titanium dioxide, instead. While lightfast extra-white watercolour paper is noticeably whiter than traditional white papers, they are not as white as optically brightened paper. This is because there is a limit to the amount of pigment that can be added to the stock without compromising the bonding strength between the paper fibres.
Similarly to extra-white watercolour papers, tinted and black watercolour papers, such as Bockingford Tinted and Stonehenge Aqua Black, are made by adding lightfast pigments to the stock. Khadi Handmade Black watercolour paper is made using black cotton rags. However, because the dyes used in the rags are not lightfast, the paper is prone to fading, particularly if exposed to sunlight.
Watercolour Paper Sizing
Watercolour paper should be absorbent enough to stabilise the paint, but not so absorbent that the colour becomes dull. Sizing provides a little water resistance, so that the paint does not sink too much into the paper, and partially sits on the surface. Watercolour paper can be sized internally, externally, or both, with gelatine, starch, or a synthetic size like Alkyl Ketene Dimer. Internal sizing is when the size is added to the water and pulp mixture before the paper has been made. External sizing (also known as tub sizing) is when the formed sheets of paper are pulled through a gelatine bath. Some papers are both externally and internally sized which increases the wet strength of the paper. Papers that are externally and internally sized are usually best for masking fluid.
All watercolour paper manufacturers size their paper differently. A wash of semi-dilute paint, without any attempt to work it into the paper, is a good test to see how a watercolour paper is sized. Watercolour papers that have been treated with a lot of size have a high resistance to water and are known as hard-sized papers. On them, dilute washes of paint will want to sit on top of the surface or even bead up. Another sign of a hard-sized paper is a feathery ‘tide mark’ around the edges of the wash, created as the paint sits on the surface and the pigment migrates to the edges. Hard-sized paper has higher abrasion resistance, and tends to withstand more vigorous painting techniques, like scrubbing and reworking of the paint. It is also ideal for lifting techniques because the colour does not penetrate the fibres of the paper and is more easily removed (depending on how staining the pigment is).
Watercolour papers that are less heavily sized (sometimes called soft-sized papers) are less resistant to water. The paint will be absorbed more readily into the paper which makes it ideal for techniques like glazing, where transparent layers of paint are applied on top of previous layers of colour. Soft-sized watercolour papers might have a softer surface texture. Sheets of handmade papers are individually sized by hand, so the sizing can vary from sheet to sheet. This is part of the character of the paper and can enhance the enjoyment of working on it. Synthetic and gelatine size is broken down by detergents present in soap, household cleaning products and even brush cleaner. Even a small amount can cause the paper to become extremely absorbent, behaving like blotting paper. If soaking watercolour paper, it’s best to do so in a dedicated tray rather than in the bath or a sink. If using a bath or a sink then it’s important to ensure that all soap residue is removed. Brushes should also be thoroughly rinsed after using brush cleaner.
Return to top of page
Why Does Paper Buckle When Wet?
Buckling occurs because paper fibres expand when wet. If you use very little water in your technique, then very little buckling will occur, if any. For more watery applications a heavier weight paper (425gsm and above) will buckle less.
Stretching watercolour paper involves deliberately saturating the paper with water in order to expand it, fixing it to a board, usually with gumstrip around the edges, then allowing it to dry before painting. Preparing your paper like this is the best way to ensure a completely flat surface.
How to Stretch Watercolour Paper
What you will need:
- A clean, soap-free tray of water, with one dimension slightly longer than the shortest edge of your sheet of paper or, if you don’t have a tray, a clean spray bottle.
- A clean, soap-free sponge or paper towel.
- A rigid board – plywood or plastic is ideal.
- 4 strips of gummed tape, to glue each edge of your paper to the board. It helps to pre-cut each length so that it is 3cm longer than each edge.
The most common and inexpensive method of stretching paper is to begin by soaking it in clean water for a few minutes (140lb weight paper will need up to 8 minutes, heavier paper may need more). If your sheet of paper does not fit in the tray you can hold it at opposite edges and feed it through the tray multiple times to ensure the whole sheet is soaked.
Lift the sheet from the tray and allow any excess water to drain from it before placing it flat on your board. If you do not have a tray simply place your paper on to the board you wish to stretch it on to, and spray generously on both sides of the paper with clean water. Try to only touch the paper on its edges as it’s possible to leave visible finger marks on the stretched paper. Sponge off the excess water gently with a clean sponge – the outward motion you use to do this will help flatten the paper onto the board. Once you feel that the paper is adequately stretched out, wet your gumstrip using a clean paintbrush or sponge, but do not immerse it in the tray of water for too long as this can wash away too much of the adhesive, and it may not be able to hold the paper in place as it shrinks.
Place the gumstrip tape on the edges of the paper so that half the width is covering the paper’s edge, and half is stuck to the board. When doing this, take care not to let water from the tape drip onto the paper, as this will leave spots on the paper when you start to paint on it. Use a dry paper towel to press the tape down, which will also soak up any excess water. Lay the board flat and allow it to dry (it may need to be left for a few hours, or overnight to be completely dry) before you start your painting.
When your painting is finished, leave it to dry completely before cutting the paper free from the board using a sharp craft knife. You can remove gumstrip from the paper by soaking it with a sponge to rewet it, and then carefully lift it off with a palette knife or craft knife.
Return to top of page
Is There a Correct Side to Work on Watercolour Paper?
Cylinder mould-made watercolour paper has two sides which vary slightly in texture. The felt side is the side which is formed in contact with the woollen felts and usually has a more irregular texture than the mould side, which is formed in contact with the wire mesh. Both sides of the paper are pressed between felts (in the case of rough and cold pressed papers), or between hot metal rollers (for hot pressed papers) later on during production, which evens out much of the difference between the two sides. If the paper is watermarked, you can identify the felt side by holding the paper up to the light and finding the side from which the watermark reads correctly.
Pads, blocks, and packs of cylinder mould-made paper are generally presented with the felt side up. However, because the paper is evenly sized on both sides, they are equally suitable for painting on. We recommend inspecting and feeling the texture on both sides of the paper before you start painting to see which one you prefer. Handmade paper is pressed between back to back felts and the texture is the same on either side. The slightest differences in texture may occur from sheet to sheet. Either side can be used.
What is a Deckle Edge?
A deckle edge is an irregular edge to the paper (as opposed to a clean edge) found on many handmade and cylinder mould-made papers. The edge is formed when some of the wet pulp goes beyond the frame of the mould.
Because handmade rag papers are individually formed, they are the only papers that have four true deckle edges. Cylinder mould-made watercolour papers only have two true deckle edges, and often the two remaining edges are torn with a specialist knife, or cut with a water-jet to create pseudo deckle edges. In the 19th century, deckled edges were seen to be imperfections in the papermaking process, and would be trimmed. Today, however, many artists find a deckle edge pleasing to the eye and like to frame their work in such a way that keeps the deckle edges on show.