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Old 07-10-17, 01:29 AM
Koo Schadler's Avatar
Koo Schadler Koo Schadler is offline
Tempera Painter
 
Join Date: Dec 2003
Location: Alstead, NH & Zirahuen, Mexico
Posts: 299
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Hi Lora,

It’s an interesting and adventuresome idea. Before discussing granulation in egg tempera, I want to look at some terms that I think can be confusing.

From what I understand (watercolorist, please chime in) granulating is when very watered-down watercolor paint settles on the paper unevenly, creating a grainy application of paint. These irregular deposits of color are referred to as “sediments”. Hence the interchangeable terms “granulating” or “sedimentary” to describe pigments that are especially good at creating granular effects.

Flocculation – the tendency of some pigments’ particles to “flock” together - is somewhat akin to granulation (in both cases the paint appears uneven) but I believe it’s distinct in that flocculated particles aren’t settling out into sediment, but instead are clumping together.

Key to granulating is (a) lots of water and (b) using the right pigments. A pigment’s tendency to granulate is often linked to large particle size, but it’s more complicated than that. It’s true that many large pigments (5 – 50 micron), such as historic earths, granulate, but so do some modest size (1 micron) pigments. From what I understand, granulation has more to do with how a pigment does, or rather doesn't, stay evenly suspended in solution, which is influenced by not just particle size but also pigment weight, amount of water, and other factors (such as a pigment’s tendency to flocculate).

In regards to egg tempera, I’ve seen granulation occur in “petit lacs” (i.e. a puddle of very watery tempera paint applied, then the tip of the brush used to pull the paint over the area to be covered). Petit lacs are so watery they don’t leave brush marks, but because they are so watery they can leave granulation, if granulating pigments are used.

I’ve applied single layer petit lacs as a quick way to cover a lot of surface area. They can appear either granulated or quite smooth depending on the pigment and technique. I think it might be a challenge to do more than one (maybe two) layers of petit lac in egg tempera; it involves so much water that you would re-wet, disturb and/or probably lift underlying paint layers if you did too many. But I haven’t tried applying more than one petit lac layer and don’t know for sure. Maybe if you let the underlying layers cure for a while, you could get away with it.

Both granulation and flocculation are more apparent on an irregular surface because pigments catch and settle in the valleys and nooks of cold pressed watercolor paper. So the typically smooth surface of a traditional gesso panel probably yields less of a granulating effect than rough watercolor paper.

Very few pigments are large enough to result in visible texture. Some historic (prehistoric to about 1700) pigments are relatively large: i.e. 50 to 100 microns (a typical human hair is 50 microns). But the majority of pigments, even many earth colors, are only 5 to 3 microns; and modern colors can be even smaller, .01 micron. A thick application of paint can create texture, but I think it’s unlikely that pigment particles themselves do - but if you’ve experienced otherwise, let us know.

One final comment, on the term “grinding”: this involves a mortar and pestle and the literal pulverizing of material. I know you’ve actually done this, Lora (having made lapis from scratch, as you once told me). But to be clear, most pigments don’t need to be “ground”; they arrive from the manufacturers already ground to an optimal particle size (in fact, some pigments, if ground too fine, change or lose their color). I mention this distinction not to be fussy, but because I don’t want beginning tempera painters to think grinding colors is part of the job; it’s not (unless you are making lapis from scratch). What tempera artists do is disperse or mill pigments; i.e. use either a muller or palette knife to combine pigments with water and egg. Neither a muller nor palette knife is strong enough to “grind” a pigment and affect its particle size.

Have you tried granulating yet in ET? Please let us know if you do. It's always great to have a new topic on the forum.

Koo

Last edited by Koo Schadler; 08-10-17 at 03:05 PM.
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