Essential tips on stretching watercolour paper

Stretching your watercolour paper before painting allows you the creative freedom to use as much water as you want, whenever you want. To avoid unsightly cockling – the wrinkling and ridging of the sheet that’s notoriously difficult to fix – it’s essential to stretch your paper, especially if you plan to use a lot of water. However, if you’re working on heavyweight paper or using gouache or acrylic, stretching may not be necessary.

Luckily, there are two effective ways to stretch your watercolour paper. We explore how to achieve both methods to elevate your watercolour painting with perfectly stretched paper.

Stretching on a flat board

What is a board?

Using a board is the most common way of stretching paper. Spruce drawing boards (draughtsmen’s boards) are the best option because they are hard-wearing and durable. However, they are not easy to find. MDF board can also be used but it should be sealed beforehand so that water doesn’t penetrate. For paper under 24in square a 12mm board thickness is suitable; for larger sheets, increase the thickness of the board to prevent warping. A thicker board is best because you can use both sides. Alternatively, you can brace the 12mm board on a frame.

What type of paper should I use?

Acid-free paper is the best paper to use if you want your work to last a long time. This is because acidity embrittles the paper and eventually makes it too weak to handle.

Whatever paper you choose, use the heaviest sheet you can afford, for the simple reason that it will be more robust and less likely to bend in long-term storage. Paper can be stretched up to a size of approximately 1.5m x 2.5m but if you go beyond that, the tension in the paper will be too strong.

What is the method?

Allow 1in for gummed paper tape all the way round your paper when cutting to size. Fill a large sink or bath with water and submerge the paper, rolling or folding it as necessary, but avoiding creasing it. A heavy paper (300lb/640gsm) must soak for 15 to 20 minutes, while a lightweight one (90lb/190gsm) needs only four to five minutes.

If the paper is too large to submerge it can be soaked on the board, but allow up to 25 minutes soaking on each side to ensure expansion of the paper.

After soaking, remove the paper and allow the excess water to drip off before lying it on the clean board. Using traditional gummed paper strip, tape down the edges and leave the board to dry flat. Both sides of the board can be used – simply stand the board on four ink bottles to let the air circulate.

Stretching on a purpose-made frame

It is also possible to purchase stretching boards or ‘paper stretchers’ from your local art store.

What happens if the paper has failed to stretch?

If the paper fails to stretch you can reuse it by cutting it off the board and going through the soaking and stretching process again. There are four faults that are the most common reasons for failure when stretching paper:

  • The paper has not soaked long enough. It looks flat when dry but still cockles when painted on. Running paper under the tap will not be sufficient to soak it.
  • Gummed paper tape, which is sometimes difficult to find, has been replaced with masking tape or brown sticky tape. These don’t stick and they don’t stretch with the paper.
  • Too wet a sponge has been used to moisten the gum strip and the gum is wiped off, preventing it from sticking.
  • Boards or frames have been stood upright to dry, making the water run to the bottom, pulling the paper away from the top. This is why paper stretching is difficult on studio walls.

Shop Winsor & Newton Watercolour Paper here.