Understanding Watercolor Paper Sizing: A Beginner's Guide

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Does watercolor paper "go bad"? Could your paper be the reason why you're unable to create the beautiful watercolor effects you so desire? How can you keep your watercolor paper in good condition for a longer time?


Watercolor is an incredibly rewarding painting medium to pursue, but to develop your skills to a higher level and achieve best results, it's crucial to understand the materials you're working with, especially the paper.

Watercolor paper isn't your average paper.

It undergoes a special process known as sizing, which significantly affects its performance and makes it suitable for water-soluble mediums. 

In this blog post (and the video included below), we'll explore what sizing is, why it matters, and how to ensure your watercolor paper remains in top condition for a longer time. 


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What is watercolor paper sizing?

​Sizing is a substance added to watercolor paper after sheets have been manufactured, during the manufacturing process, or both, which gives it its strength and allows watercolor paint to perform as it should. 

It is thanks to paper sizing​ that we're able to create beautiful effects when working with watercolor and why this paper is able to handle lots of water without getting damaged.  

Sizing can be derived from animal, plant, or synthetic sources.


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Why Sizing is Important

Sizing plays a key role in how watercolor paper performs as we're working.

More specifically, here are three key areas it impacts:

      1. Absorbency: It affects the speed at which the paper absorbs water and paint that have been placed on it. When paper has good sizing, the paint sits on the surface a bit longer and it allows for an even dispersion, which prevents splotchiness and patchiness. Bad sizing leads to paint "sinking in" too quickly, which leads to lots of lines, marks and undesired textures. 

      2. Color Vibrancy: Well-sized paper helps colors look bright and vibrant. With poor sizing, colors "sink in" and end up looking flat. 
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      3. Strength and Durability: Sizing adds stiffness and strength to watercolor paper, which not only protects it from wear and abrasion, but also leads to less warping/buckling during the painting process. 

Paper on left showing bad sizing (splotchiness, dull/sunken color, and undesired texture). Paper on right showing good sizing (soft transitions between colors, easy wet-on-wet effects, no undesired lines/marks/texture).

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Recommended Watercolor Paper

Arches Cold Press 140 lb 100% Cotton Watercolor Paper

Saunders Waterford Watercolor Paper

Stonehenge Aqua Cold Press 140 lb 100% Cotton Watercolor Paper

Fluid 100 Cold Press Watercolor Paper

Check out my Watercolor Supplies 101 masterclass for everything you need to know on paper types (Cold Press, Hot Press, Rough), brushes, and paint formats.

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Recognizing Bad Sizing

For beginners, it can be challenging to identify when paper sizing has gone bad.

Here are some telltale signs:

• Paint immediately sinks into the paper, often soaking through to the back.
• Because paint dries so quickly (imagine dropping in watercolor on to a kitchen paper towel), we're left with lines and texture that we weren't looking for. 
• Colors look dull and pale.
• Difficulty achieving wet-on-wet effects (see image above).
• Presence of white dots or specks in painted areas.
• Uneven drying, with some sections remaining wet and others drying too quickly. *Oftentimes sizing starts going bad along the edges of sheets, which are less protected from humidity and other environmental factors. 
• Sometimes the edges of our shapes appear fuzzy, even when we're painting to dry paper. 

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Watercolor paper showing bad sizing. Notice those specs and the patchiness created by the quickly sinking color in the red rectangle?

Watercolor paper with bad sizing showing lines or visible edges left behind by quickly drying brush strokes. Paint dries so quickly, you're unable to fill in a small shape, even when working fast.

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Tips for Maintaining Your Watercolor Paper

​To keep your watercolor paper in the best condition, consider these practical tips:

• Quality Matters: Invest in high-quality paper, like Arches, which tends to have better sizing. Use student-grade paper for practice and high-quality paper for final pieces.
• Buy Smart: Avoid buying large quantities of paper at once, even if it's a sale! Purchase what you need for the next few months only. 
• Storage: Store paper away from humidity and moisture. If you live in extreme conditions, use an airtight container.
• Check Before You Buy: When purchasing large sheets, try buying them in person from an art supply store and choose freshly opened packages.

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Art Supply Storage and Organizers Airtight Plastic Containers

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Sterilite Large Clip Boxes Storage and Organizers Airtight Plastic Containers

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What to Do with "Bad" Paper

If you find that your watercolor paper's sizing has deteriorated, don't throw it away! 

Here are some ways to repurpose it:

• Drawing: Use smooth (hot press) paper for pencil or pen drawings.
• Other Mediums: Use rough or cold press paper for gouache or other opaque painting mediums.

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Understanding watercolor paper, what kinds of paper to invest in, and how to store your paper, is very important. 

By recognizing the signs of bad sizing you can also avoid unnecessary frustration and also confusion, as you'll be able to tell that something may not be turning out because of your supplies and it's not your lack of skills. 


If you found these tips helpful, don't forget to share this post with your art friends!

Have any questions or tips of your own? Leave a comment below.

For more watercolor tips and tutorials, subscribe to my YouTube channel and follow me on Instagram.

Thanks for reading and enjoy your art practice!

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