Stretching Watercolor Paper: How and Why

The idea of stretching watercolor paper was one that I found strange. My first thought was “how and why would do I do that?“

After looking into it, I discovered that this process doesn’t actually stretch the paper.  Instead, it involves thoroughly soaking the watercolor paper so that the fibers “plump” and the paper size expands slightly. Then, while it’s still wet, you staple it down to a board, and as it dries, it contracts slightly against the staples, and this flattens and smooths it. 

In addition, soaking the paper also removes some of the sizing. Sizing is a wash that the paper manufacturers apply to paper to change the way it absorbs paint or ink.  Sizing is usually is made of some sort of gelatin, which if applied in excess, can impede the absorption of paint more than desired. Therefore, some artists like to remove some of the sizing via the stretching process. Now the caveat here is that you don’t want to remove all of the sizing, so you must limit how much time you soak the paper. In listening to other artists, 10 minutes seems to be the upper time limit for soaking the paper. 

Here's how to stretch watercolor paper. (Not that you'll need a piece of gatorboard a little larger than the paper you want to stretch, a regular household stapler and a water source.)

  1. First, if you plan to paint a drawing of your subject, create your drawing on the paper first. 
  2. Then soak the paper. Use either in a CLEAN waterproof tub, or hold the paper under a stream of warm running water.
  3. Once the paper is wet and limp, you then place it on a stiff backing board, with the side you want to paint on up. 
  4. The paper may have some ripples or bubbles in it. That's okay. Don't pull on the paper.  You can straighten it by lifting and placing it again on the board, but don't pull on it or try to stretch it manually.
  5. Now you'll staple it down.  Start the staples on one short edge, and then, WITHOUT pulling the paper taut, staple the other short edge. Then continue stapling the long edges until all sides are tacked down.
  6. As the paper dries, it will contract slightly against the staples and once dry, it will be smooth and flat on the board.

These steps are from a great video about stretching watercolor paper made by Colorado artist Lorraine Watry.  She first shows how she transfers her drawing to the paper and then starts the stretching process at 14:37.

Stretching Watercolor Paper:  Why?

The purpose of stretching watercolor paper is to keep the paper from buckling when you paint on it.  If you ever added a bunch of water to a loose sheet of watercolor paper, you’ve seen how it buckles. This is because the fibers where you are painting get wet and expand while the rest of the paper stays dry. Stapling or taping the paper edges down securely before you start painting stops this from happening. 

Keeping the paper flat is important because if your paper buckles while you are painting, you can get paint color running into areas that you didn’t intend.  In addition, once it dries like that, you won't be able to frame the painting. Hence, it’s best to tack it down before you start to paint.

Stretching watercolor paper is useful for larger paper sizes, such as 11” x 15" or more.  Smaller paper sheets can be taped down as they are, without going through a stretching process.  Some artists will tape and staple dry watercolor sheets down to the backing board to minimize buckling.

Choosing the Right Backing Board

I recently learned how stretching watercolor paper can go wrong when you try to go the cheap route.  I bought a full sheet of Arches watercolor paper and used Lorraine Watry’s technique to stretch it onto a board. She recommends using gatorboard, but when I went to buy gatorboard, I found that it was quite expensive.  So I went to my local art store, and found some board that had a foam core with a hard outer shell just as she described.  I thought it was the same thing as gatorboard. Nope.

The picture below shows the result.  The paper is perfectly flat and the staples held, but the board bowed.  That will be awkward to paint on, but that's my lesson learned. Next time, I’ll shell out the extra money to buy REAL gatorboard, which is much stiffer than this cheap foamcore board.  

Or maybe I'll just avoid the whole soaking/stretching process all together.  After watching this great video by Steve Mitchell over at the Mind of Watercolor, I'm thinking there are better ways to prevent paper buckling.  

I'll be looking into buying a commercial stretcher, some 300 lb paper and some watercolor board, since I agree, stretching watercolor paper is a pain, and gatorboard is expensive.  

Painting Already Buckled?  You Can Fix it...

If you have completed, dry paintings that are buckled and warped, you can fix them with these steps:

  1. Turn the painting over and lay it facedown on a clean dry towel.
  2. Use a spray bottle, brush or a sponge to wet only the back of painting, working on it until the paper gets limp.  
  3. Once the back of the painting is wet, take it off the towel and place it facedown on a blank sheet of watercolor paper of the same size.  Make sure the surface on which you lay the paper stack is completely flat and dry. (And old pad of inexpensive watercolor paper is helpful for this.)
  4. Add another blank sheet of watercolor paper on top, effectively sandwiching the painting face down between two pieces of clean watercolor paper (I use an old Caslon pad to do this). 
  5. Place a heavy weight such as a stack of books or glass cookware on top of the paper sandwich/pad, and let it sit overnight.  When you take it out the next day, the painting should be dry and flat.

Here's a short video for a visual demonstration of these steps:

If you have any questions, ping me on Facebook, or send me a message from my contact page.  I'll do my best to answer them.

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