Flattening a Watercolor Painting; Things You Can’t Miss!

If you paint on unstretched paper, your works may dry with huge buckles. You’ll need to flatten your watercolor paintings before framing them. There are some methods you can use to get rid of them and get a flattened watercolor painting. In this article, we’ll discuss them so it would become easier for you to know how to flatten your painting.

How to Flatten a Watercolor Painting


Fortunately, there is a simple solution: you can iron your watercolor paintings. Many painters have utilized this approach as a do-it-yourself flattening technique for years.

You must first prepare your equipment, which includes a clothes iron and a spray bottle. Check that they are both clean and filled with distilled water. Turn on the iron and select the “cotton” setting. Then, on your floor, place one big acid-free mat board. 

Place your first painting facing downwards on the board, spray the back lightly with water, and iron it carefully. If some creases remain, use a burst of steam to massage them out. When you have many paintings of the same size, iron them separately, one on top of the other, with clean sheets of paper in between. 

Finally, lay another piece of mat board on top of the paintings and weigh it down with books overnight.

Everything usually comes out as flat as a pancake! If any creases remain, repeat the procedure. Test the method on scraps before attempting it on any significant works, as the results of different papers and colors may vary. If you use Arches Watercolor Cold Press and Daniel Smith watercolors, you would hopefully never harm a painting.

Flattening a Transparent Watercolor Painting on Paper

When painting on watercolor paper using transparent watercolor, the material frequently buckles and remains that way until dry. This article describes one method for flattening the paper using a temporary ‘paper press.’ 

This approach is ideal for paintings composed of thinly applied glazes and washes of transparent watercolor on paper, and the procedure includes a water danger, therefore caution is advised. This method is not a recommendation for impasto painting methods. 

Thick applications of watercolor paint include a larger amount of binder and humectant than highly diluted watercolor, and the thicker paint may adhere to the blotting paper. A supplies list and step-by-step instructions are given below.

We propose practicing and testing with sacrificial applications of the same watercolors on the same paper before flattening a genuine painting.


  • A flat place on which the assembly can sit for several days.
  • Clean blotting paper (or equivalent thick, absorbent, acid-free paper) in sizes larger than the artwork! These interleaving sheets will absorb the moisture from the painting.
  • Two clean, flat boards that are somewhat larger than the artwork
  • Using a jar of water, clean a sponge, sponge brush, or lint-free cloth.
  • You can use stacks of art books and gallons of water as weights.
  • The painting
  • If desired, you can use Polyethylene plastic to protect the working surface.


  • Prepare the transparent watercolor artwork for flattening.
  • Make sure there is no lotion or other substance on your skin by washing your hands.
  • Place the plastic on a level working surface.
  • Set one of the boards on the plastic.
  • Place a clean blotting paper sheet over the board. The blotting paper should be bigger than the paper used for the painting. The purpose of the blotting paper will be to absorb moisture and allow the wet watercolor paper to dry.
  • Wet down the back of the artwork.
  • Water may harm a watercolor painting, so proceed with caution.
  • Place the painting face down on a clean, flat surface and softly soak the back with a little moist sponge, sponge brush, or lint-free cloth.

Note: Try to achieve an equal coating of wetness (rather than pools of water), and be especially cautious to keep the water to the rear. Water seeping in from the margins or through the paper itself might re-wet the watercolor and harm the picture. 

Papers lighter than 140 lb./300 g.s.m. will absorb even less water, and there is a larger risk of water soaking through the paper from the back and affecting the painting.

  • Assemble the improvised “paper press”.
  • Place the artwork on top of the blotting paper. You may hang the painting with the paint side up or down.
  • Line the edges of a clean piece of blotting paper with the edges of the first piece of blotting paper.
  • Place the second board on top of the second blotting paper sheet, followed by the weights.
  • Replace the blotting paper afterward.
  • Take the layers apart the next day and replace the moist blotting papers with dry sheets.
  • Rep this process until the blotting papers and the back of the painting are dry.
  • Replace the existing blotting paper sheets with fresh, dry ones one last time. Reassemble the layers and let them lie for another day or two to ensure that all of the moisture has gone from the watercolor paper.
  • Take away the flattened artwork.
  • Remove your temporary ‘paper press’ for the last time, and your painting should be flat. If it is not flat, continue the process using dry blotting paper sheets.

Final Verdict

Be careful not to damage the painting by soaking the back of the paper, and be aware that the procedure may diminish the amount of surface roughness apparent on Cold Pressed or Rough watercolor paper. 

This method works nicely with 140 lb. / 300 gsm. watercolor sheets and heavier watercolor papers. When using thinner papers, it’s a good idea to test how moist the back of the paper may be safely before flattening an actual painting. 

Flattening the paper today does not prevent the risk of future buckling when the material responds to moisture in the environment.

Follow the instructions carefully if you want to flatten your watercolor painting. These tips and tricks would help you a lot in flattening your paintings in a very professional manner and without even letting your paintings get damaged, but the concentration is the key.