Prior to the mid-18th century, watercolor artists handmade their paints by mixing powdered pigments with sugars and/or hide glues or some other binder and preservatives. Brothers William Reeves and Thomas Reeves invented the moist watercolor paint-cake in 1781, at the start of the “golden age” of English watercolor painting. The “cake” was immediately soluble when touched by a wet brush; a time-saving convenience.
William Winsor secured the patent for the metal paint tube invented by American oil painter John Goffe Rand. Winsor improved the design by adding the screw cap in 1904 and started manufacturing the Winsor & Newton moist watercolors in tubes.
Today, watercolor paints are sold in tubes and pans in a variety of sizes. Tubes are the most commonly used and are sold in sizes 5ml, 10ml, 14ml, 15ml, 21ml, and 37ml depending upon the manufacturer’s brand. Pans come in full-pan and half-pan sizes.
Where Watercolor Pigments Come From
Watercolor paint begins with pigment, the finely ground substance that provides color. Historically, pigments were derived from natural sources such as minerals, plants, insects, and metals. Famous examples include ultramarine made from lapis lazuli and carmine derived from cochineal insects.
Modern watercolor paints rely primarily on synthetic pigments. These pigments are engineered to provide greater color consistency, improved lightfastness, and safer handling compared to many historical pigments. While the names of some colors remain traditional, their chemical composition has often changed significantly over time.
Pigment Grinding and Particle Size
Before pigments can be made into paint, they are milled and ground into fine particles. The size of these particles plays a critical role in how watercolor paint behaves on paper.
- Larger, heavier particles tend to settle into the paper’s texture, creating granulation.
- Smaller particles disperse more evenly, resulting in smoother washes.
- Particle size also affects transparency and staining properties.
Natural earth pigments such as ochres, siennas, and umbers tend to granulate more due to their heavier particle structure, while many modern organic pigments produce smooth, flat washes.
The Role of Gum Arabic in Watercolor Paint
Once the pigment is prepared, it is mixed with a binder—most commonly gum arabic. Gum arabic is a natural resin harvested from acacia trees, primarily grown in parts of Africa.
Gum arabic serves several essential functions:
- It binds pigment particles together.
- It allows paint to adhere to watercolor paper.
- It influences flow, sheen, and rewetting ability.
Different manufacturers use varying concentrations of gum arabic, which is one reason watercolor paints can feel and behave differently from brand to brand, even when using the same pigment.
Additives Used in Watercolor Paint Manufacturing
In addition to gum arabic, watercolor paint contains small amounts of additives that affect performance and longevity.
Common additives include:
- Glycerin, which improves moisture retention and helps paint rewet easily.
- Honey, used by some manufacturers to enhance softness and flow.
- Wetting agents, which help paint spread evenly across damp paper.
- Preservatives, which prevent mold growth during storage.
These subtle differences in formulation contribute to each brand’s unique handling characteristics.
Tube Watercolor Paints
Watercolor paints in tubes are soft and moist. They are made with natural or synthetic pigments suspended in a binder of gum arabic with glycerin added as a wetting agent. By reading the label on the tube, you will discover the pigment formula number(s), transparency rating, lightfastness rating, staining property rating, and an approved product seal.
Tube vs. Pan Watercolor Paints: How They Are Made
Although tube and pan watercolor paints may appear similar, they are manufactured differently.
Tube paints are poured while still fluid and sealed to retain moisture. Pan paints are typically poured in multiple layers and allowed to dry slowly between pours. This process creates a firmer cake that withstands repeated wetting.
Some manufacturers use the same paint formulation for both tubes and pans, while others adjust binder ratios specifically for pan strength and durability.
Understanding Pigment Numbers on Paint Labels
Pigment numbers are standardized internationally and provide valuable information to artists. Each code begins with letters identifying the color family (such as PB for blue or PR for red), followed by a number that identifies the specific pigment.
Pigment numbers matter because:
- Color names can vary between brands, but pigment numbers do not.
- Single-pigment paints produce cleaner color mixes.
- They help artists avoid unintended color shifts or muddiness.
Learning to read pigment labels is an essential skill for watercolor painters.
Lightfastness Testing and Paint Permanence
Lightfastness refers to a pigment’s resistance to fading when exposed to light. Modern watercolor manufacturers test their paints using controlled ultraviolet exposure over extended periods.
Results are often rated according to industry standards, allowing artists to choose colors that will remain stable over time. This testing is one reason modern professional watercolor paints are significantly more reliable than historical formulations.
Environmental and Safety Considerations in Modern Watercolor Paints
Many traditional pigments are no longer used due to toxicity, environmental impact, or scarcity. Synthetic pigments allow manufacturers to replicate historic colors while improving safety and sustainability.
Occasionally, pigments are discontinued or reformulated as regulations change, which is why some familiar colors may disappear or return under new formulations.
Watercolor Paint Manufacturers
Here is a list of popular watercolor paint manufacturers in alphabetical order:
- Daler-Rowney (Great Britain)
- Daniel Smith (Washington USA)
- Da Vinci (California USA)
- Grumbacher (Massachusetts USA)
- Holbein (Japan)
- Schmincke (Germany)
- Sennelier (France)
- Winsor & Newton (Great Britain)
Other Watercolor Mediums
- Gouache – an opaque watercolor with a higher pigment density and white chalk added
- Liquid Watercolors – resembles ink and is sold in small dropper bottles
- Watercolor Sticks – resembles crayon or pastels that can be used dry or wet
- Watercolor Pencils – resembles a lead pencil but contains dry watercolor pigment
Why Professional-Quality Watercolor Paint Matters
Professional watercolor paints contain higher pigment loads, fewer fillers, and undergo stricter testing for consistency and permanence. Student-grade paints are often made with imitation pigments and extenders that reduce color strength, mixing clarity, and longevity.
Recommended
My favorite manufacturers of watercolor paints are Daniel Smith and Holbein in tube size 15 ml, and Winsor & Newton in tube sizes 14 ml and 37 ml. I recommend and use only professional-quality watercolor paints. NOTE: Student-grade watercolor paints are mostly made of imitation pigments of low quality.