Ox gall

Electric Cat Dude

Needle-chuck Ninja
I’ve been on a quest over the last few months to find a solution to spraying very fine lines with an airbrush repeatably and reliably.

Call me crazy but when I own a high end airbrush like an Iwata Custom Micron or similar, I expect them to behave like a professional instrument that works on demand when properly maintained. What I was getting was a tool that would not live up to the fine line test samples included in the box by Iwata. I’ve done several things to improve the situation. First I’ve switched over my paints from Iwata’s ComArt paint to Holbein’s Acryla Gouache in 20mL tubes. This didn’t solve the tip buildup problem, but a resulted in a much smoother and finer pigment with better coverage and opacity. My next step was the follow Kim McCann’s advice and polish the taper of my needles to a mirror finish using a jeweler’s rouge. This again improved the tip buildup problem and consistency doing fine lines - but only to a point. My next step was experimenting with certain dilutions of water with Winsor & Newton’s Acrylic Flow Improver. I found that I could achieve very fine and consistent lines using a 100% mixture of the flow improver, but it is severe price. The high concentration mixture of flow improver will inhibit the ability of the gouache to adhere and cure to the subtrate. This makes it susceptible to flaking and lifting when Frisket masks are used.

Beginning to run out of options, I returned to a book in my library, The Illustrator’s Bible by Rob Howard and read the chapter on gouache again. Ox Gall has been used by watercolor artists for many years to improve flow and blending of paint and to improve drying. Howard’s book recommended the use of Ox Gall to improve the flow of gouache paint, and stated this was popular with airbrush illustrators for limiting clogging problems.

Out of desperation, and a little skeptical that it would work, I ordered a 40 mL bottle of Holbein Ox Gall. When it arrived, I made a mix in a 1 ounce dropper bottle of 1 ounce of water to 15 to 20 drops of ox gall and used that for mixing with the tube gouache. I was pleasantly shocked by the results. Not only did it eliminate the inconsistency and limitations on doing fine lines, but it solved the coverage problem and fragility when placing adhesive Friskets on top of it.

To test this, I used an Iwata Custom Micron CM-B with a polished needle taper. Paints are Holbein Acryla gouache on a medium press sketchbook paper. I sprayed both fine lines and a heavy area coverage. Below is a test of the gouache reduced with the water and ox gall mixture.


The heavy area coverage was than covered with a piece of frisket film overnight, then the frisket was peeled off and the piece was examined. The ox gall mixture seems to have not only sprayed fine lines very well and repeatably, but gave excellent coverage in a heavy application which was resistant to adhesive backed masking film. NOTE: small white patch in lower left hand corner was a negative workability test using an electric eraser, which it passed.

Next I attempted a similar test using the 100% Windsor and Newton Acrylic Flow Improver to reduce the Gouache.


This flow improver mixture passed the fine line test, though not as well as the ox gall mixture did. But it then failed miserably when the frisket was applied over it and left to sit for six hours. You can see how much paint was lifted off by the adhesive on the frisket.

My conclusions are that the ox gall, when mixed with water in trace amounts solved the fine line problems without affecting the ability of the paint to cure. This stuff really does work!

I’ll continue to conduct tests on this. Specifically I’m curious to see how ox gall would work with Createx or ComArt paints, or used in airbrushes which do not have hand polished needles.
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Very interesting read. The performance of waterbased acrylic is something that frustrates me too. It’s improved from my own experiments with pressure and reduction, but some extra help would be great.

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Additional tests using the same airbrush and subtrate. Red paint was Iwata ComArt airbrush paint with a 20:1 ox gall dilution (one drop ox gall to 20 drops of paint). Blue paint was Createx Illustration thinned using a 20:1 water/ox gall reducer.



Iwata ComArt: Fine line capability was significantly increased, though skipping was present as was frequent tip buildup. Heavily applied paint field was resistant to lifting from Frisket film.

Createx Illustration: Results similar though inferior to the ComArt. Fine line capability is increased but does not exclude skipping. Some lifting was noted from Frisket film, but more tests are needed here to draw a definite conclusion for Createx.

Additional concerns of mine or this may be an unfair comparison between the ComArt and Createx paints, as Cretex does not come out of the bottle properly thinned for use through a fine art airbrush. I would have to find a way to uniformly formulate the reducer for each.
Nice work. I'm also doing some experiments to see what I can use with more maintream inks we have over here. With E'tac it was not necessary. Some Condition-Air in the water and it was perfect. Perfect lines every time. I'm also playing with some gouache now but in a bottle, not tube, so it is a bit thinner already. So far just some retarder in water has yielded some good results.
I found this thread really interesting and sent me half way down a rabbit hole and was surprised that someone way back when actually thought, if I put gall bladder juice in paint it will flow better.
Talk about random.
Ox gall is use to make Bile soap. When mixed with alcohol it was use for marbling paper and to aid in paint reduction . But most feel it is the alcohol that actually aided in the reduction of the paint and not the gall itself.
I work with a ink and paper conservator at my day job and he gave us a few classes on things like Ox gall and Iron gall ink.