How to Prestretch Watercolour Paper

Students carry a lot of supplies to and from art class. It can get heavy and bulky. For a simpler alternative to prestretched paper (as described below), see the article to the right.

Purpose

When watercolour paper gets wet, it buckles in unpredictable ways. This "hills and valleys" effect is much more difficult to paint on than a flat paper. Prestretching the paper will greatly reduce this effect.

Supplies

  1. A board of soft wood such as pine, cut to just slightly larger than the watercolour paper you like to work on. For example, many artists like working on a quarter size sheet. This measures 11 x 15 inches, so a board approximately 13 x 17 inches or larger would suit this size of paper
  2. A spray can of Varathane non-yellowing varnish to coat the board with. This is to protect your watercolour paper from the oils in the wood. In turns, spray both sides of your board and let it dry well. Alternatively you could coat the board with white or off-white latex paint if you have some around.
  3. Watercolour paper cut to the size you prefer to paint on. 
  4. A clean sponge or cloth and a stapler.

Procedure

  1. Put a few inches of cool to lukewarm (not hot) water into a clean sink or bathtub and lay your cut watercolour sheets into this. You can do several sheets at a time, as long as you have a board for each. If you are using Bockingford paper, set a timer for 5 minutes to let the paper soak well. If you are using Arches, it takes only about 2 or 3 minutes to be saturated. If you see gray spots suddenly appearing in your paper, take it out immediately - too much of the sizing has disolved out in those places.
  2. Remove the paper and gently smooth it on top of a prepared board with a clean sponge or cloth.
  3. Starting in the middle of any side, staple the four edges of the paper to the board. Place the staples about 1 inch apart, and about 3/8 inch in from the edge.
  4. Lay the board flat and let the paper dry. This can take an hour or more depending on the weight of paper and humidity. (I prefer to do this chore the night before and let it dry overnight.)
  5. The paper is now "prestretched" and ready for you to paint on. Do not take the paper off the board, or take the staples out, until you are finished the painting and it is dry.

Although it is called "prestretching" this process would be better named "shrinking". Good quality watercolour paper is 100% cotton, and by wetting it and stapling it, you are causing it to shrink tight like a drum cover on the board. As long as you leave it stapled to that board, the next time you wet it (when painting), it will not stretch out as much.

Frequently Asked Questions

Q This seems like a bother, are there any other ways of managing the paper?
A Some artists use bulldog clips to hold the watercolour paper onto the board. As the wet paper stretches, they just open a clip and pull it tight again. You may also hear of artists using gummed packing tape instead of staples. I find the tape messy to remove, and you lose more of the edge of the paper in order to have it stick adequately. Lastly, if you work very wet, the tape lifts and the paper buckles again.
Q What about buying the watercolour pads that are sealed on the edges?
A These pads are great for taking travelling or painting outdoors. Because you leave the paper attached by the edges until you are finished each painting, it doesn't buckle as much. However, the paper has not been prestretched and if you work quite wet, it will still make those unwanted hills and valleys. I have heard of artists wetting the top sheet of the pad with a sponge, and letting it dry before working on it. That should help. 
The major disadvantage of the sealed watercolour pads is their cost. It is a lot cheaper to buy the paper by the sheet and prepare it yourself.
Q Should I buy a staple gun for prestretching paper?
A Large staple guns are not recommended simply because it is so difficult to get the staples out of the wood when you are finished the painting. Smaller hobby staple guns may work, however, this is not necessary. A good quality stapler should staple into a pine board. You will find that it works more easily to bite the wood with the stapler rather than opening the stapler up.
Q What about a staple remover?
A It is better to use a butter knife to slip under the staples. You can slip it under both paper and staple if that is easier. The claw shaped staple remover can damage the top of the paper.
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