Gouache, water, and the ratio that finally flowed

2026-01-25 · 3 min read

I wanted to letter a set of place cards in white on dark gray card for a dinner in February, and white ink from a bottle was giving me either a watery gray or a clog in the nib. Gouache is the usual answer, and I had read that you mix it “to the consistency of single cream,” which is one of those phrases that means nothing until you have gotten it wrong several times. I kept a record this time so I would stop guessing.

The setup: a small palette well, a tube of white gouache, distilled water in a dropper bottle, and a pointed nib on a straight holder. A pea-sized blob of gouache from the tube is about 0.5 ml. My first mix was that blob with 10 drops of water, stirred with the back of a brush. Too thick: the nib held it but it would not release onto the paper, and the strokes started and stopped. Second mix, 20 drops: it flowed but went translucent, and the gray card showed through the hairlines. Third mix, 15 drops: close, but it still skipped on the upstroke.

What actually fixed it was not the water ratio but a drop of gum arabic solution, which the books mention as an afterthought. One drop into the 15-drop mix and the behavior changed completely. The gouache stayed on the nib, released cleanly, and dried to an opaque matte white with sharp edges. I think the gum gives it a surface tension that plain water does not. The final working recipe, written on a card taped to the desk, is one pea of gouache, 14 to 16 drops of water, one drop of gum arabic, stirred for a full minute and left to sit for two before loading.

The other lesson was about loading. A pointed nib wants to be dipped so the ink covers the vent hole, then touched to the rim of the well to drop the excess, then a single test stroke on scrap before the real card. Skipping that test stroke cost me three cards out of the first ten, each with a blob where the first downstroke landed. The mix also thickens as it sits; I added a drop of water every 15 minutes and that kept it steady over an hour and a half. Thirty cards finished, two spares, and the gray card took the gouache without any feathering at all, which the bottled white ink never managed.