How to Test Watercolor Pigments
Testing watercolor pigments helps you predict how a paint will behave before it reaches your palette or finished artwork.
With a few simple tests, you can compare brands, spot unreliable colors, and build a palette that matches your painting style.
The best part is that you do not need a lab setup to get useful results.
A sketchbook, watercolor paper, water, and a consistent testing method can reveal far more than a tube label ever will.
Why pigment testing matters
Watercolor paint can look similar in the pan or tube but behave very differently on paper.
Two paints with the same color name may differ in composition, pigment load, staining behavior, or resistance to fading.
Understanding those differences helps you make smarter choices in several areas:
- Palette selection for landscape, portrait, botanical, or urban sketching work
- Mixing consistency when you want predictable secondary and tertiary colors
- Layering control for glazing, lifting, and correcting mistakes
- Archival quality when you need lightfast pigments for sale or display
Many professional watercolorists rely on pigment information rather than marketing names.
The pigment code, such as PB29 for Ultramarine Blue or PY150 for Nickel Azo Yellow, tells you much more than the color name alone.
What you need before testing
You can test watercolor pigments with basic supplies.
The goal is to keep the setup consistent so your results are easy to compare later.
- Watercolor paper, ideally 100% cotton and cold press or hot press depending on your usual practice
- A brush with a medium point for washes and line work
- A pencil and ruler for labeling swatches
- Clean water and a palette
- Artist tape or washi tape for clean test areas
- A daylight-balanced lamp or indirect natural light
- A notebook or digital spreadsheet for recording results
- Optional: masking fluid, a spray bottle, and UV exposure space for lightfastness checks
If possible, use the same paper for every test session.
Paper strongly affects how pigments appear, especially for transparency, staining, and granulation.
How to test watercolor pigments step by step
A good testing process evaluates both appearance and behavior.
The following method gives you a reliable overview of how each pigment will perform in real paintings.
1. Create labeled swatches
Start by labeling each pigment with the brand name, color name, pigment code, and batch if available.
Paint a small rectangle or circle for each color, leaving space for notes.
Make one swatch at full strength and one diluted wash.
This shows the color range from saturated to transparent and helps you compare staining strength.
2. Test transparency and opacity
Transparency affects glazing, layering, and the brightness of underlying paper.
To test it, paint the pigment over a drawn black line or a checkerboard pattern.
If the line remains clearly visible, the pigment is transparent.
If it becomes muted or disappears, the paint is more opaque or semi-opaque.
Useful examples include:
- Transparent pigments for glazing and luminous layers
- Semi-transparent pigments for balanced flexibility
- Opaque pigments for cover, corrections, or body color
3. Check staining and lifting
Staining pigments sink into paper fibers and resist lifting.
Non-staining pigments are easier to rework, soften, and remove.
To test, paint a wash and let it dry fully.
Then wet the area with a clean brush or water and lift with a tissue or damp brush.
Observe how much color moves.
Strongly staining pigments are useful for vibrant shadows and crisp layers.
Non-staining pigments are better when you want to lift clouds, highlights, or soft edges.
4. Observe granulation
Granulation occurs when pigment particles settle unevenly into paper texture, creating mottled effects.
Some artists love this natural variation, while others prefer smooth, uniform washes.
Paint a broad wash and let it dry undisturbed.
Granulating pigments often separate into speckles, pools, or textured patterns, especially on rough or cold-press paper.
Common granulating families include many earth pigments and mineral-based colors, but behavior varies by brand and formulation.
5. Evaluate flow and wet behavior
Flow tells you how easily a pigment moves through a wet wash.
Some paints spread quickly and create soft blooms; others stay where you place them.
Try dropping pigment into a damp wash and watch the edges.
Note whether the paint blossoms, feathers, or remains controlled.
This matters for skies, florals, wet-in-wet landscapes, and controlled detail work.
6. Compare drying shift
Many watercolor pigments dry lighter or darker than they appear when wet.
This drying shift affects how you judge value and saturation while painting.
Paint a swatch and compare it after drying.
Record whether the color changes significantly, because a strong shift can cause mistakes in value planning.
7. Test mixing behavior
Mixing tests show whether a pigment behaves cleanly or muddies other colors.
Pair each pigment with a few key neighbors from your palette, such as a blue, a yellow, and a red.
Watch for secondary hues, neutralization, and unexpected browning.
Many painters prefer single-pigment colors because they usually mix cleaner than multi-pigment blends.
How to test lightfastness
Lightfastness is one of the most important properties for artists who display, scan, or sell their work.
It describes how well a pigment resists fading when exposed to light over time.
Check the manufacturer’s lightfastness rating first, but do not rely on it alone.
Independent testing and your own records provide extra confidence, especially with less familiar brands.
Simple at-home lightfastness test
Paint a swatch strip on watercolor paper and divide it into two sections.
Cover one section with opaque tape or card stock, then expose the paper to indirect sunlight or a bright window for several weeks.
When you remove the cover, compare the protected and exposed sections.
Any visible fading, color shift, or loss of strength suggests the pigment may not be suitable for archival use.
For more reliable results, test multiple pigments at once and label the date.
Keep in mind that home tests are useful for comparison, but they do not replace standardized lab ratings such as ASTM lightfastness categories.
How to read pigment labels and codes
Pigment labels are often the fastest way to understand watercolor quality.
The pigment code identifies the actual colorant used in the paint.
- PB means Pigment Blue
- PY means Pigment Yellow
- PR means Pigment Red
- PG means Pigment Green
- PBr means Pigment Brown
- PW means Pigment White
- PBk means Pigment Black
A single-pigment paint usually behaves more predictably than a mixture containing several pigments.
Multi-pigment paints can still be useful, but they may mix more softly or produce duller results.
Also look for terms such as transparency, semi-transparent, staining, granulating, and lightfast.
These descriptors are helpful, but they should be confirmed with your own tests whenever possible.
How to organize your test results
Without a system, pigment testing can become confusing quickly.
A simple catalog makes it easier to reference colors months later when you are building or revising your palette.
Use a format that works for your workflow:
- Swatch cards stored by color family
- A watercolor journal with notes beside each sample
- A spreadsheet with columns for brand, pigment code, transparency, staining, granulation, and lightfastness
- Photos taken under consistent lighting for digital comparison
Include practical notes such as “excellent for glazing,” “too opaque for layering,” or “granulates beautifully on rough paper.” These observations are often more useful than technical data alone.
Common mistakes when testing watercolor pigments
Even careful artists can skew their results by changing too many variables at once.
Avoid these common mistakes to get cleaner comparisons.
- Testing on different paper types without noting the difference
- Using too much or too little water between swatches
- Comparing wet swatches to dry swatches
- Ignoring pigment codes and relying only on color names
- Assuming every brand’s version of a color will behave the same
- Skipping lightfastness checks for artwork meant to last
Consistency is more important than speed.
A smaller set of well-documented tests is far more valuable than a large, unrecorded batch of swatches.
Which pigments are worth prioritizing?
If you do not want to test every paint in your collection at once, begin with the colors you use most often.
Many artists start with core primaries, earth tones, and a few specialty pigments.
High-priority categories include:
- Primary reds, yellows, and blues for mixing
- Earth pigments for landscapes and portraits
- Transparent darks for shadow work
- Granulating blues and browns for texture
- Convenience greens and violets, if you frequently use those hues
This focused approach lets you build an efficient, dependable palette without overbuying duplicate or underperforming colors.
What to look for in a reliable pigment
A reliable watercolor pigment is not always the most dramatic color on the page.
In most cases, the best choice is the one that behaves predictably for your intended technique.
Look for a pigment that matches your priorities in these areas:
- Consistent color strength
- Clear pigment labeling
- Suitable transparency for your layering style
- Acceptable lightfastness for your work
- Mixing behavior that stays clean rather than muddy
- Effects such as granulation or staining that support your subject matter
When you test watercolor pigments carefully, you move from guesswork to informed selection.
That makes palette building more efficient and painting decisions more confident from the first wash to the final detail.
