Water Colour Surfaces: A Go-To Glossary

water colour paper glossary

Whether you’re a seasoned water colour painter or new to the discipline, knowing the most important water colour surface terminology will ensure you choose the ideal surface for your work. 

Be sure to bookmark this page, your go-to glossary of water colour surface-related terms, to help you make the best decision about which surface is ideal for your artistic practice.

Produced by using cotton linter or wood-free fibre, acid-free paper is pH neutral, which is essential for the long term stability of paper. 

Buffering allows a sheet to counteract atmospheric acidity over time. It is achieved by adding an alkaline filler such as calcium carbonate to the sheet at the pulp stage.

Water colour papers are traditionally white, allowing the maximum amount of light to be reflected back through the wash. Conversely, tinted papers give a mellow tone to a painting. (See: the visual example below for more.)

A ‘deckle’ is the frame which is used to make paper. ‘Four deckle edges’ is a common phrase which indicates that a sheet is mould-made, simulating the look of hand-made paper. (See: ‘Mould Made Paper’ below for more.)

External sizing
This refers to a layer of gelatine on the surface of paper which enables water colour film to sit atop it, look brighter and allows it to be sponged off by the painter. 

Bonus fact: External sizing is also known as gelatine surface sizing and creates a harder surface, which allows scraping and rubbing without damaging the paper itself.

An example of artwork as painted on two different coloured surfaces, one cream (left) and one green (right)

Internal sizing 
Internal sizing reduces the absorbency of paper fibres by chemically bonding to them.
Mould-made paper
Some paper is formed with a cylinder mould. Fibres are arranged at random to mimic a hand-made sheet, and the arrangement provides dimensional stability, reducing cockling (wrinkling).

Rag content
100% rag means paper is made from 100% cotton. Here, the term ‘rag’ dates to an era when old rags were used in handmade paper mills.
Bonus fact: Today, the cotton used in papermaking still comes directly from the plant and is called cotton linter, whereas ‘wood-free’ paper is made from chemically processed wood pulp and produces an acid-free sheet which is less costly than cotton.

The ‘Right’ side
The right side of paper is the side from which you can read the watermark. While either side can be used, painting on both sides isn’t recommended.

 Winsor & Newton Cotman Water Colour Postcards and Cotman Water Colour Pad

Surface: Rough
This is the heaviest texture of paper. It is embossed from the surface when the sheet is being dried and is used by water colour artists who rely on a more textured surface.

Surface: Not or Cold Pressed 
Not or Cold Pressed paper is a Rough sheet which has been cold pressed to flatten out the texture. It is the most popular texture used by water colourists. 

Bonus fact: ‘Not’ paper often produces the brightest water colour paintings because its increased surface area holds more colour, therefore reflecting more light.

Surface: Hot Pressed
Illustrators and miniaturists use Hot Pressed papers; a smooth paper finish blends with their images more comfortably.  

Bonus fact: Pastel papers tend to have a mechanical, ‘grained’ surface, which helps to hold pastel or charcoal on the paper. Printmaking papers tend towards the smooth end of the scale.

Water Colour Blocks
Water Colour ‘Blocks’ consist of several paper sheets of paper glued around all four edges to keep paper flat whilst painting, eliminating the need to stretch paper prior to painting.  A small section is left unglued to enable a palette knife to remove the finished work, one sheet at a time.  

Bonus fact: Blocks are excellent for painting en plein air. Read more of our plein air painting tips here

Heavier paper is more resilient to wear and tear, as there is more interwoven fibre in a heavy sheet. Lightweight papers should be stretched if you expect to use lots of water. 

Bonus fact: Many water colourists prefer heavier papers as they are able to take heavier washes without cockling (wrinkling). 

Weight measurement: Imperial and Metric

Imperial weight is that of 500 sheets of Imperial sized [30” x 22”] paper.  A lightweight water colour paper might be 90lb. The Metric weight is grams per square metre (gsm). A 90lb. paper is equivalent to 190gsm.

Looking for more information about how to choose a surface for water colour? Read about the top three things you should look for when choosing a surface, and our article on how to stretch water colour paper for more.