Confused about whether to use Rough, NOT, CP or HP watercolour paper? Don't understand your gsm from your lb? Find out all you need to know about watercolour papers with our easy-to-understand guide.
How do handmade and mould-made watercolour papers differ?
1. Discover handmade watercolour paper
What is is handmade watercolour paper and how is it produced?
Originally all paper was made in this way:
- A vat of cellulose (usually cotton fibres) and water with added size is mechanically agitated to maintain consistency.
- A frame with a fine wire mesh is swished into the pulp then lifted out with a mat of pulp, which has formed on the mesh.
- The mat is turned out onto a woollen felt. This felt is placed with others to form a pile (post) of felts and paper within a press.
- When the press is full, the water is squeezed out and, at the same time, the paper receives the texture of the felts.
- The paper is peeled off the felts and hung to air dry in a loft. It may then be dipped into a vat of size to give a harder surface and again dried.
2. Discover mould-made watercolour paper
What is mould-made watercolour paper and how is it made?
The cylinder mould machine was developed to imitate the actions of hand papermaking.
- The cylinder is set in a tank filled with a fibre and water mixture.
- As the cylinder revolves the fibres are drawn on to the cylinder mesh and they mat there.
- The wet mat of paper is taken off (couched) on to woollen felts, whose weave will determine the finished paper texture.
- It then contains about 80 per cent water, reduced to about seven per cent, by pressure and heat.
What is sizing and why is it necessary?
Size is added to the pulp tank or dipped afterwards to prevent a blotting-paper and less absorbent surface.
Better quality papers are normally internally sized and surface sized after being made, creating a harder surfaced paper that helps lift out techniques and reduces damage when working vigorously.
Different types of cellulose
Cotton fibres are used in handmade papers. These are naturally acid free, white and strong, making a tough paper, which will retain its whiteness and integrity for centuries.
In the early 19th century, the demand for paper burgeoned and a cheaper substitute for cotton was sought.
Wood pulp was the answer, and still is, but wood pulp contains lignin, an acidic substance that causes paper to go brown and brittle.
A way was found to remove the lignin content, rendering its cellulose acid free.
The name for the treated fibre is ‘wood free’. This paper is not as durable as cotton, but it still has a life expectancy of 200 years or so.
Understanding watercolour paper textures
The finished paper texture is directly created by the felts when the paper is ‘couched’.
There are three different textures, which will differ depending on manufacturer:
- Rough - The most deeply textured of the three, preferred by those creating expressive and impressionist techniques.
- NOT or cold-pressed - NOT means not hot-pressed, in other words, cold-pressed. This surface is from less coarse felts, giving a gentler texture. This is the most popular texture, with sufficient character for dry-brush effects, but permitting detailed treatments.
- Hot-pressed - From NOT-surfaced felts the paper is passed through heated metal rollers to flatten it to a smooth finish. Originally done to create paper for books, it is ideal for those watercolour painters who like to use fine detail or pen-and-wash techniques.
Understanding watercolour paper thicknesses
Watercolour paper’s thickness is expressed in two different ways.
You may see weight in ‘lb’ (pounds) per ream for a specific size of paper, mostly now Imperial size (30x22in.).
The metric measure for paper is gsm (grams per square metre); 300gsm is equivalent to 140lb.
As a rough comparison guide: lb to gsm, double it; gsm to lb, halve it.
Which weight of paper should I use?
- The most common weight is 140lb (300gsm), which is thick enough to take modest washes without buckling too much.
- Lighter weight paper will cockle if not pre-stretched.
- Substantial 300lb (600gsm) is more like card, which shouldn’t give any distortion problems.
- Really hefty 600lb is suitable when working large or very wet.
How does the price of watercolour papers differ?
In rough terms you will find that mould-made cotton paper is twice the price of mould-made ‘wood free’ paper, and handmade paper is twice the price of cotton mould-made paper.
Which watercolour papers should I try?
Find out with reviews from from top artists
1. Haidee-Jo Summers reviews Strathmore 500 watercolour papers
Back of Millfield Terrace in Winter, watercolour and acrylic ink (sepia), on Strathmore Gemini 500 638gsm paper, (18x28cm)
2. Explore a range of watercolour papers from Canson with Tony Paul
Cazals from the Fields, watercolour on Canson Moulin du Roy 300gsm hot-pressed watercolour paper, (17x20cm)
3. Discover Hahnemühle watercolour papers with Tony Paul
Tom, watercolour on 600gsm (280lb) Leonardo matt (NOT) watercolour paper, (40x30cm)
4. Take a look at Winsor & Newton Professional Watercolour paper with Deborah Walker
Between the Salt Water and the Sea's Strand, watercolour on Winsor & Newton Professional Watercolour Paper 140lb (300gsm) Rough, (48x84cm)