The following article was written by artist Sarah Becktel.
What is granulation?
Granulation is an interesting characteristic of watercolor which causes the paint layer to look textured or mottled. This textured appearance is caused by pigment particles clustering together rather than staying evenly dispersed within the layer of watercolor paint. This clustering creates areas of darker color (where the pigment is dense) and areas of lighter color (where the pigment is sparse.)
Watercolor paint is primarily composed of pigment (the color) and a binder such as gum arabic. Whether a watercolor will or will not granulate is dependent on the pigment(s) used in that color. Pigments with larger or irregularly shaped particles tend to granulate more, while pigments with small, round, homogenous shaped particles tend to granulate less.
Is there any way to predict whether granulation will occur?
Pigments are typically categorized as either “inorganic” or “organic.” Inorganic pigments typically do not contain carbon and are primarily made with minerals that can be further combined or processed to create the final pigment product. Traditional earth colors made with iron oxide (such as siennas and umbers) and colors made with metals (such as cobalt blue and cadmium red) are some examples of inorganic pigments.
Organic pigments contain carbon and are created either from animal/plant matter or by using synthetic organic chemistry. Most organic pigments used in art materials today are man-made synthetics because these are more durable and lightfast than animal and plant-based organic pigments. Examples of synthetic organic pigments are quinacridone red, phthalo blue, and dioxazine violet.
Generally, watercolors made with inorganic pigments tend to granulate more than colors made with organic pigments. This is because organic pigments have very small and regularly shaped particles, which creates paint that produces an even application of color. Inorganic pigments often have larger and more irregularly shaped particles. This causes the particles to clump together and settle unevenly on the paper, which creates granulation.
In the image above you can see a side-by-side comparison of two MaimeriBlu watercolors on Strathmore 400 Series Watercolor paper. On the left is Cerulean Sky Blue, which is made with an inorganic pigment, and on the right is Primary Blue Cyan, which is made with an organic pigment. The Cerulean Sky Blue is showing granulation, while the Primary Blue Cyan is not.
However, the production of pigments can vary from manufacturer to manufacturer, and knowing whether a pigment is organic or inorganic is only one factor in determining whether a color will granulate. For example, there may be 2 different companies that produce a watercolor paint from the same inorganic pigment. One company uses a version of that pigment that is more finely ground, while the other uses a version that is more coarsely ground. Even though they are using the same pigment, the finely ground version will granulate less, and the coarser ground version will granulate more. Therefore, categorizing inorganic pigments as granulating and organic pigments as non-granulating is a helpful starting point, but it is a generality rather than a concrete rule and you will probably come across colors that do not fit within this framework.
Before purchasing new watercolors, I recommend checking out a brand’s website for both product information and color charts. Some brands include granulation information right in their literature or packaging, and many brands also have color charts that show painted swatches on paper. MaimeriBlu’s online color chart is a great example; each color swatch shows the watercolor applied to a textured watercolor paper and it is very easy to see which colors granulate and which do not.
Can I control granulation?
Although we can’t completely control granulation, there are ways to manipulate the appearance or amount of granulation. One way to influence granulation is with the paper surface you are working on. A cold press or rough watercolor paper has a very textured surface with high points and low points. These textured surfaces encourage granulation because the pigment particles will clump and settle in the low points of the paper texture. Hot press or mixed media surfaces tend to have a smoother surface texture. Granulation will still occur on these papers, but the granulating pigment particles will move and settle randomly, and the granulation may look less pronounced since these papers don’t have prominent hills and valleys of texture.
The image above shows MaimeriBlu Cobalt Green watercolor applied to four different Strathmore papers. Each paper has a different surface texture which subtly affects the appearance of the granulation.
Another way to manipulate granulation is to experiment with the amount of watercolor paint you applied to the paper. When a large amount of liquid is applied to the paper, the pigment particles can easily move around and settle into the low points of the paper. This creates a pronounced granulation effect. When less liquid is applied to the paper, the pigment particles don’t have the ability to move and flow as much, so there will be less visible granulation.
The image above shows two samples of MaimeriBlu Potter’s Pink applied to the same surface: Strathmore 500 Series Imperial Watercolor Paper (cold press.) For the sample on the left, I loaded up my brush and applied a large amount of the watercolor mixture to the paper. For the sample on the right, I used less of my paint mixture and applied it to the paper with a drier brush.
Finally, granulation can be manipulated by mixing colors together. If you mix a non-granulating color with a granulating color, the granulation effect will be apparent in the mixture, and you can experiment with different amounts of each color to get your desired amount of granulation.
In the image above, I’ve mixed MaimeriBlu Potter’s Pink (which granulates) and MaimeriBlu Permanent Violet Blue (which does not granulate.) You can see granulation in the resulting mixture, and you can also see some separation of the two pigments within the mixture. In the darker areas with more granulation, the color leans towards Potter’s Pink, and in the areas with less density of granulated pigments, to color leans towards the Permanent Violet Blue.
Granulation is a fun and unique feature of watercolor that I hope you’ll all be inspired to explore. Experimenting with the possibilities of organic and inorganic pigments, paper surfaces, and application techniques can create endless possibilities for incorporating granulation into your art.
Sarah Becktel is an American artist based in Southern New Jersey. She earned her BFA in painting from the Tyler School of Art and continued her studies of representational drawing and painting at multiple locations. Sarah has shown her work in solo and group exhibitions throughout the United States and her work is in private collections across the world.
Sarah creates paintings and drawings that are inspired by animals, natural history, and ecology. She travels extensively to view animals in their natural environments and many of her works are a result of her experiences in nature. Sarah also finds inspiration in natural history museums where she can study and learn about the animal species of bygone eras.
When Sarah is not working in her studio or traveling, she is educating artists and students about their mediums and materials. As an Artist Educator for Strathmore Artist Papers, Sarah lectures at art schools and ateliers about the characteristics of art materials and how to choose the right products for each artist’s individual needs. She served as Product Research Director for the Colored Pencil Society of America from 2009 to 2015, which led to a rich understanding of lightfast testing and art materials manufacturing.
You can see more of Sarah’s work here: