You may have seen ox gall (or oxgall) listed as an ingredient in watercolor paints. Many well-known brands use it in at least some of their colors, including Winsor & Newton, Da Vinci, and Schmincke Horadam. Other brands, such as Daniel Smith and QOR, use a synthetic substitute. So what is it, and what’s it doing in your paint? And, is there ever any reason to add more of it?
What is ox gall?
Basically, it’s all in the name. It’s the gall, or bile, of oxen – or really any sort of bovine. Cows, like us, make gall to aid digestion, especially of fats. Gall is stored in the gallbladder, which is connected to the liver. The active ingredient as far as paints are concerned are various salts which are natural surfactants (chemical compounds that lower the surface tension between two liquids or a liquid and a solid). Envision a laundry detergent commercial where the grime is lifted off of the surface of the fabric and washed away – those are synthetic surfactants at work. They allow the water to penetrate the fabric and the stain. In fact, in the days before Tide, housewives made their own stain remover from ox gall.
The stuff in your paint is pretty much just straight up gallbladder juice, which is collected from bovine gallbladders – a byproduct when beef are slaughtered. The gall is then purified and dehydrated using a chemical process, and may later be reconstituted with alcohol. A vanishingly small quantity is in your paint – one drop from an eye dropper would be enough for many pans.
Ox gall seems like such an esoteric product. Who makes this stuff, and why?
I would love to talk to someone involved in commercial gall processing! Despite a great deal of online searching and a chat with someone who used to work in a large slaughter house, I was unable to find out anything about where modern ox gall is coming from. There is some information from patent records about various chemical processing methods, and you can also buy the dehydrated gall in bulk from laboratory supply houses.
Although modern surfactants are easily available, ox gall seems to still have many uses in this day and age. It’s used for paper marbling as well as watercolor paints; is a flavor-booster in packaged meat products, such as gravy; is used in scientific experiments to replicate human gall; and perhaps most intriguingly, is a key component for making TB vaccinations, which also show promise in warding off Alzheimer’s. (If you’re up for a tangent, check out this article from The Guardian).
What’s it doing in my paint?
Surfactants are helpful in the paint manufacturing process, as they help the water/gum arabic solution mix evenly into powdered pigment so that it surrounds each particle. This is especially true for many of the modern synthetic organic pigments, which tend to repel liquid. Some manufacturers add ox gall only to some colors, probably because it’s more necessary for grinding some pigments. Manufacturers may also add oxgall as a dispersant to help standardize the way paints made from different pigments flow on the paper, so they are predictable across the brand. This may or may not be desirable for you. Personally, I like working with the idiocentricities of different pigments.
My guess (based on using paints with synthetic and real oxgall) is that using real oxgall is mainly a matter of tradition, rather than imparting working properties that are distinct from the synthetic stuff.
Should I add more ox gall to my paint?
Ox gall does two things, which you may or may not want to happen:
- Helps the water/paint mixture penetrate the paper surface, making it sink more deeply into the paper and “stick” to hard-sized paper. This makes the paint more difficult to lift – useful for glazing.
- Makes the pigment disperse through the water in a very wet wash, resulting in more even washes, and diminishing or changing the effect of granulating pigments.
Some folks may want to have maximum control over these characteristics, in which case you could seek out paint brands, such as Rublev Colors, Sennelier, or M. Graham, which don’t use any surfactants/dispersants. Even if your paint has oxgall to start with though, it’s a very small amount, and you can change its characteristics by adding more.
Ox gall and synthetic substitutes are available from many watercolor brands. It’s powerful stuff, so one little bottle will likely last you for years. You’ll want to dilute it with water. Some common ways to use it are to mix a few drops into your wash water or to eye-dropper diluted Oxgall into a paint mixture on the palette.
Next week, I’ll share all about my DIY work-in-progress – harvesting and purifying my own ox gall! If you haven’t already, subscribe so you’ll stay in the know. In the meantime, I’d love to hear about how others use oxgall in their work. Share in the chat!
