How to Test Watercolor Paint for maximum performance!

February 11, 2023

Knowing how your pigments will behave will can give you more insight when you are using them! In this post, I’m going to show you how you can test your watercolor paints so that you can learn more about them!

Let’s get into it…

Why should you test your watercolors?

Why bother testing your paints in the first place? How could this help you?

The answer is rather simple, the purpose of testing your watercolor paints is to be able to better understand how your specific selection of pigments will behave on the paper. To avoid unwanted surprises.

Which brings me to my next question, what qualities are you supposed to look for when testing your watercolor paints? The answer is Transparency, Granulation, Permanence, Masstone/Undertone, Staining, and Diffusion. Let’s go through each one in more detail and how to test for them!

How to test different Watercolor paint qualities:

Transparency/Opacity

One of the characteristics of watercolor paint is that it’s transparent. Meaning, when you apply a layer of paint on another layer the previous layers can be seen through. If you add a new layer onto the paper, the light can still travel through the layer of paint, reflect off the white of the paper and create a beautifully luminous effect.

Some pigments are more transparent than others. This is why testing for transparency can come in handy, you will know beforehand which colors to use when layering.

Transparency can be tested by drawing a line of waterproof ink, (you can use a sharpie), and then swatching the color you want to test on top. If the colors are more opaque, they’ll leave a chalky residue.

You can also test the transparency level of a color against another by glazing them on top of each other.

Granulation

To make watercolor paint, the pigment is ground into a smooth fine powder. However, some pigments have larger grains than others. When the layer of paint is drying, the pigment separates and sinks into the wells of the paper to form a textured dotted effect as shown in the image below. This is process is called granulation.

Different colors granulate on the paper at different rates. This is because while some pigments are easier to grind into a fine powder, others are harder and create slightly grainy results. A good example of this is Ultramarine.

How to test for granulation?

To test for granulation you simply have to dilute the pigment and then paint the color onto the paper. Now, all you have to do is wait for it to dry to see the results. Using rough textured paper or cold-pressed paper will be more effective than hot-pressed.

Lightfastness

Lightfastness, also referred to as permanence refers to how durable the paint is in a given time frame when exposed to light. Permanence happens because of exposure to light, the chemical bonds of the paint begin to break. This happens over a certain period which causes the watercolor paintings to fade, darken or become discolored, over time.

Companies usually include a “permanence rating” which indicates the level of durability the pigment has against light exposure. The rating is usually written on the label or the company’s website and changes between brands. However, you can test this for yourself.

How to test for Lightfastness?

You can test the lightfastness by swatching the color you want to test and then putting it in a place where it’s exposed to direct sunlight. After a certain amount of time, you can then paint a fresh swatch of the same colors and note down if there are any differences. Because different colors have different permanence ratings, it may take much longer to see any difference with certain colors.

I am currently running a permanence test and will update this post with the results when it’s complete in 6 months and 12 months.

Masstone/Undertone

Masstone and undertone, also referred to as “Hue shift”, are terms to describe what the paint looks like straight from the tube (saturated) compared to what it looks like watered down (diluted).

Masstone- Saturated paint from the tube
Undertone- Diluted watered down version of the paint

How to test for masstone and undertone?

To test the masstone and undertone of your colors, simply swatch a saturated version on one side and then swatch a diluted version next to it.

Alternatively, you can also start by painting a long strip. Start with the saturated pigment straight from the tube, and slowly add little amounts of water as you move the brush along. The image below shows both versions:

Staining

Staining watercolors are paints that, when you work with them, the paint is absorbed by the paper and becomes difficult to rewet, remove, or rework. Some pigments are “non-staining”, meaning they can be lifted off the paper with little to no effort. This is especially useful when lifting off paint in watercolor reflections or highlights!

You can test your pigments if they’re staining by using a paper towel or a dampened brush to lift the paint at two different stages. The first stage is to lift the pigment while the paint is still wet. The second stage is to let the layer of paint dry, then rewet a small section and try lifting the pigment after.

Level of dispersion (diffusion)

Watercolor paint tends to “bleed” when you paint into wet paper. The level of dispersion refers to how quickly and how far the pigment spreads when painting. Colors that spread farther and quickly will mix with other colors more than pigments that don’t really spread out.

Here’s how to test for the level of dispersion:

Draw long rectangular boxes which will be your test strips. Make sure each box is the same size for more accuracy. I drew mine 5cm × 1cm
Wet the first box with clean water and load your brush with the color you want to test
Drop the color into the box from the left end by dabbing 2 to 3 times depending on how big your box is. I dabbed 3 times for each color.
Let the pigment dry without disturbing it. As it’s drying you’ll be able to see how far the pigment travels across the test strip
For more accuracy try to wet the boxes with the same amount of moisture. Only work with one box at a time, you don’t want them to start drying while you’re testing the other colors.

The images below show the step by step process:

You can see the final results in the image below. You’ll also see how the first color (french ultramarine) didn’t spread too far. This is because I didn’t wet the paper enough and the paper dried before the paint had a chance to spread.

How to further understand your paints?

After swatching your watercolor paints and testing them, you might wonder if there’s anything else you can do to become familiar with your palette. In this case, I would advise color mixing charts! This way you can understand what colors can be mixed from the pigments you have on hand.

I have also written an article about many of the different types of watercolor mixing charts! Be sure to check it out to learn more.