Why Do Some Watercolors Granulate?

Some watercolors dry into a perfectly smooth wash.

And some seem to spend the entire drying process rearranging themselves.

Pigment gathers in the texture of the paper, tiny darker areas appear, the wash becomes mottled or almost stone-like, and occasionally two colours that looked completely mixed five minutes ago start separating again.

That is granulation.

And the slightly annoying answer to why some watercolors granulate and others do not is that it depends.

Mostly on the pigment.

But also on the paper, the amount of water, the way the paint was made and what you decide to do with it while it is drying.

It starts with the pigment

Watercolor pigment is made from tiny particles, and those particles are not all the same.

Different pigments have different particle sizes, shapes, densities and behaviours in water.

Some pigments stay suspended very evenly in a wash. They tend to dry fairly smoothly.

Others are heavier or have larger particles. As the water moves and eventually evaporates, those particles settle into the little valleys in the watercolor paper.

That is what creates the visible texture we call granulation.

So granulation is not really an effect added to watercolor afterwards.

It comes from the physical behaviour of the pigment itself.

Which is one of the reasons I find pigments so much more interesting than just colour.

Two paints can look almost identical when they are wet on a palette and behave completely differently once you put them on paper.

Some pigments are simply much better at it

Certain pigment families are famous for granulating.

Cobalts are a good example. Many earth and mineral pigments granulate too, and some modern pigments produce extremely strong granulation or separation.

Others barely granulate at all.

And then you can put several pigments together and things get even more interesting.

If a paint contains pigments with different particle sizes, weights or characteristics, they may move differently in the water.

One might settle quickly.

Another might travel further.

Suddenly you have colour separation as well as granulation.

I can spend a ridiculous amount of time watching this happen.

Occupational hazard, apparently.

Paper changes everything

If you have ever bought a beautifully granulating watercolor and then wondered why it is doing absolutely nothing, try changing the paper.

Watercolor paper has a surface texture, usually described as hot pressed, cold pressed or rough.

Hot pressed paper is relatively smooth.

Cold pressed has more texture.

Rough paper has a lot.

Granulating pigment settles into those tiny dips and valleys, so the more texture the paper has, the more visible the granulation can become.

The same paint can therefore look surprisingly different on different papers.

It is one of those things that makes watercolor slightly impossible to judge from a single swatch.

And then there is water

More water gives pigment particles more freedom to move.

A generous wet wash often allows granulation to develop much more clearly than a dry, heavily worked brushstroke.

Then comes the difficult bit.

Leave it alone.

Watercolor continues moving after you stop painting.

If you keep brushing back into the wash while it is drying, you are moving all those particles around again.

Sometimes that is exactly what you want.

Sometimes you have just destroyed the beautiful thing the pigment was halfway through making.

I have done both.

Many times.

Does handmade watercolor granulate more?

Not automatically.

A handmade paint does not become granulating simply because somebody made it by hand.

The pigment still determines a huge part of the behaviour.

But the recipe matters.

The ratio between pigment and binder, how thoroughly the pigment has been dispersed, the ingredients in the binder and whether other materials have been added can all influence how a paint behaves.

When I make Art to Basic watercolors, I work from dry pigment and build the paint in layers. I do not add fillers simply to increase the volume of paint.

I want the character of the pigment to remain part of the finished watercolor.

That means some colours are beautifully smooth.

Some granulate.

Some separate.

And some are frankly a little dramatic.

They are usually my favourites.

Can you make a watercolor granulate more?

To a point.

You cannot turn every naturally smooth pigment into a wildly granulating one just by wishing very hard.

But you can give a granulating pigment better conditions.

Try more textured paper.

Use enough water to let the pigment move.

Make a larger wash.

Try not to fiddle with it while it dries.

And experiment with mixing granulating pigments with smoother ones.

You can get some extraordinary textures from very simple combinations.

There is also no single correct amount of granulation.

Sometimes I want a huge geological explosion across the paper.

Sometimes I just want the slightest broken texture in a shadow.

That is the lovely thing about it.

You put down the paint.

You give it water and paper.

And then, for a little while, the pigment gets a vote too.