The easiest way to flatten a watercolor painting

How to flatten a watercolor painting

There’s nothing more satisfying than having your watercolor painting in a crisp straight form. Watercolor paper tends to buckle or warp when painting, that is why I decided to share methods you can use to flatten a watercolor painting.

How to Flatten Your Painting Step by Step

To flatten your painting all you will need is a flat surface, a spray bottle with clean water, another flat surface to place on top (like a board or a glass sheet), and something heavy.

  1. Start by placing the painting’s back side up on a flat surface. (Make sure it’s clean)
  2. Take a spray bottle and lightly spritz clean water over the back, be careful not to use too much water. Next, spread the water so the paper is evenly wet. (You can also use a sponge or watercolor brush)
  3. Use a fresh sheet of sketch paper or plane paper and cover the painting.
  4. Take a flat board (or a glass sheet) and lay it over the painting (make sure the whole painting is covered).
  5. Add something heavy like weights or some thick books on top of the board
  6. Let the painting flatten and dry for at least 1 whole day.

The diagram below shows images for each step that you can use as a reference:

If your board is big enough you can also flatten three or four paintings at the same time! The image blow shows the results after using the method above:

Can you use an iron to flatten a watercolor painting?

The short answer is yes. However, you must never use the iron directly on the paper or you risk scorching it. Instead, place a towel in between the iron and the paper.

How to straighten a watercolor painting with an iron

Note: Make sure you set your iron on medium or low heat, you don’t want to scorch your painting.

  1. Place the painting face side down on your evenly flat clean surface and very lightly spritz it with clean water.
  2. Using a watercolor brush or a sponge, spread the water so the paper is evenly wet.
  3. Place a clean towel or plane paper on top of the painting.
  4. Iron on top of the towel. If you used plain paper instead of a towel make sure to set the heat setting to medium or low.
  5. Remove the towel and place a fresh sheet on top and cover with weights or heavy books. You can also use a flat board or glass instead of paper.
  6. Leave the painting to flatten for at least 1 day.

Why does watercolor paper curl?

When you add water, the paper absorbs moisture and this causes the fibers to expand. As the paper continues to dry, the fibers contract causing the paper to warp and curl. With the methods above, the paintings dry while being compressed, allowing them to flatten.

How to prevent your paper from warping?

Instead of finding ways to flatten a watercolor painting you can also try a few things to prevent or reduce warping.

  1. Stretching your paper– This works by soaking the watercolor paper wet and then stretching it onto a flat board and allowing it to dry overnight. That way the paper won’t buckle when you paint on it. The downside of this method is that it is time-consuming.
  2. Using heavy weighted paper– You can always opt for using thicker paper that can handle more washes of wet paint.
  3. Using watercolor blocks or a board– Using watercolor paper in the form of a block where all four sides of the sheet are glued down. This can be very handy and can help prevent your paper from warping.


Even though taking preventative measures can help, most of the time your paintings can still buckle and curl to a certain degree. Instead of taking more time to prep your paper, I find it’s a lot easier to set up a “flattening station” and use the methods above. This way I also don’t feel tedious while waiting for the paper to be ready so I can get to the good part!

That’s it for this post, I hope you found the information on here helpful! Make sure to sign up for my email list and receive the free resources:

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