MITRA Forum Question Details

You are doing nothing wrong. Each pigment will create a different “feel” and rheological effect when made into a paste. In fact, some will not really make a paste at all, they will remain fluid until the point where so much pigment has been added that it is unworkable and underbound. I generally appreciate these differences and exploit them to create certain effects. Another neat thing is to use paints containing stabilizers/thickeners to create some effects and paints without these additives to create others. Rembrandt’s paintings would look vastly different if his lead white was not ropey (what you call stringy).

Anyway, that is not the thrust of your question. I have not used Omyalite, but since it appears to be a extremely fine calcium carbonate, it should work. I would caution against adding it in great quantities creating an underbound paint film.

The old DYI way to avoid this is to grind your pigments into linseed oil that has 2% or less of beeswax gently melted into it. This is generally thought to be below the point where the beeswax could contribute solubility to the paint. I have avoided this. A more modern method would be to pre-gel your oil by carefully mulling a small amount of aluminum stearate into your oil before mulling the pigment into the mixture. I have also done this after the fact by mulling the AS in very small amounts into already made, overly runny paints.

Perhaps others have thoughts on this.

​As Brian wrote stringiness is a factor related to the chenical and physical interaction of the pigment and binder. Adding aluminum stearate to the oil prior to grinding the oil with pigment will mitigate this effect to large degree, but then you will have the consequences of this additive in your painting. You may also try using a different extender pigment, instead of fine particle chalk, such as mica, which tends to eliminate stringiness with some pigments.

​The optimal amount has been determined to be 2% by weight (of oil) to improve pigment suspension, stabilize loose oil and avoid perceptible dilution of color.  https://cool.culturalheritage.org/waac/wn/wn23/wn23-3/wn23-304.html