What Are Fillers in Watercolor Paint?

I talk about fillers quite a lot, mostly because I don’t use them, and every now and then I realise that this probably makes perfect sense to me because I spend an unreasonable amount of my life making paint, while everyone else may quite reasonably be wondering what on earth I am talking about.

So. Fillers.

At its simplest, watercolor paint is pigment held together with a water-soluble binder, traditionally gum arabic. The pigment gives you the colour. The binder makes it possible to turn that pigment into paint, put it into a pan or tube and reactivate it again later with water. Depending on the maker, there may also be things like honey, glycerin or preservatives in the recipe to change how the paint pours, dries, stores and reactivates.

And then there can be fillers.

Fillers are additional materials used in paint that are not the colour pigment itself. They can be used for several reasons: to change opacity or texture, to alter handling, to make a particular formulation work and, yes, sometimes simply to increase the volume of paint without increasing the amount of expensive pigment by the same amount.

That last bit is the reason I became interested in them in the first place.

Pigments can be expensive. Some are very expensive. And if you are making thousands or millions of pans of watercolor, there is obviously an enormous financial difference between a paint containing a very high proportion of pigment and one where some of that volume comes from something cheaper.

That doesn’t automatically make every filler evil. Paint formulation is chemistry, and manufacturers make choices for all sorts of reasons. But it does change what is actually in the little pan you are buying, and I think that is worth knowing.

When I started making my own watercolor, I wanted to work as directly with the pigments as I could. I buy dry pigments and make my binder from gum arabic with honey, glycerin, guar and preservative. The paints are poured into the pans in several layers and then left to cure for weeks. I don’t add fillers simply to bulk them out.

Partly because I don’t see the point.

If I have bought a beautiful pigment because I want to make paint from that pigment, I want the finished paint to behave like it. I want to see what it does in water, how it settles, whether it granulates, how transparent or opaque it naturally is and how it behaves on different papers.

Pigments already have personalities of their own. Some are wonderfully easy. Some are stubborn. Some make perfectly smooth washes and some wander around the paper doing whatever they please. Some granulate enormously. Some stain everything they touch. Some take more work to turn into a good pan.

I rather like all of that.

It is tempting to think that more pigment must always mean better paint, but watercolor isn’t quite that simple either. You cannot just keep adding pigment indefinitely and expect to create increasingly magnificent watercolor. Pigment and binder have to work together. Too much or too little of either changes the paint. A good formulation is still a balance.

And different pigments require different things.

That is also why handmade watercolor is not simply dry pigment with a splash of gum arabic stirred into it. If only. Each pigment absorbs binder differently, wets differently and behaves differently while the paint is being made. There is a lot of adjusting, testing, swatching and occasionally staring suspiciously at a bowl of paint wondering why it has decided to behave differently today.

But that is exactly the part I am interested in.

I am not trying to make every pigment behave identically.

I want to make it into usable watercolor while keeping as much of its own character as possible.

You may sometimes see fillers discussed alongside extenders, additives and opacifiers, and those words are not always interchangeable. There are legitimate formulation reasons for adding materials other than pigment and gum arabic, and an ingredient can have a functional purpose rather than simply being there to make a paint cheaper. So I would be wary of any very simple rule saying that a watercolor containing an additional ingredient is automatically bad.

What matters to me is knowing why something is there.

If an ingredient improves the binder, preservation, rewetting or stability of my paint, fine. I use ingredients for those reasons too.

If its main purpose is to replace pigment with inexpensive bulk, I would rather leave it out.

There is another reason for that, especially with granulating pigments. The physical character of the pigment is part of the painting experience. Those tiny particles moving through water and settling into the paper are what create the textures I love. I don’t particularly want to tame all of that until every colour behaves like the one next to it.

A watercolor pan is tiny. That is part of what I find slightly wonderful about it. You can have minerals, earth pigments, modern synthetic pigments and colours with completely different histories and properties sitting next to each other in a box smaller than your hand.

I want the interesting bit inside that tiny pan to be the pigment.

Which is why, when I say that Art to Basic watercolors are made without fillers, I am not trying to turn it into a complicated purity contest.

It is simply how I want to make paint.

Pigment is the expensive bit.

Pigment is the unpredictable bit.

Pigment is also the reason I am making watercolor in the first place.

So I would rather put that in the pan.