MITRA Forum Question Details

Ha, you would need more patient with this pigment. it is known of hard to make, that each manufacture use different addictive to make the paint. so it is hard to know nor they will tell you how to make it. but just add surfactant or beeswax and slower grinding will help.

BTW, if you make this color, why donot you make from the real stone? that is easier to make. Sythetic one is not. 

also, had you tried PV29, which is ultramarin violet, does that behave same like sythetic PB29 or easy to form paint without addctives? 

Hello there,

I know it's trendy to make our own colours/cosmetics at home but this is an illustration of why industries have taken that job against homecooking. 

This pigment is difficult and there are too many parametres to control, 90% of which you forgot to mention here. Making it impossible to give you a correct answer out of the blue (sorry for the pun).

What's the quality of your pigment? Synthetic or natural? Grind? Surface treatment? How much do you grind it and by which process? Time for mixing and strength of grinding? Time of wetting and time of grinding? Wetting agent kind? Oil kind(s) and quality? What PVC are you aiming for? Why Al stearate and not coconut oil? (it's a joke). Why beeswax ? (not a joke).

This pigment is notoriously difficult, because it's not as inert as most mineral pigments which are less reactive oxides. As good looking as it is.

Depending on the billion parametres above and forgotten, from the physical properties and chemistry of all your materials and the mechanical processes used to manufacture your colour, it will turn softer or harder over time.

Best way to go is to keep it as simple as possible:

Thickened linseed oil, pigment, grind.

Just from the ratio of the only two raw materials and all the differences in time and strength or method of grind, you can still make it go stringy or stiffer depending on what you do. So best to keep it simple as that on paper, and fine tune your % and your process. 

As much as raw materials are the visible part of the colour, the process of manufacture is the hidden part of the iceberg that will make all the repeatability and reliability (and quality) of your colour.

It's like cooking in that on the absurd end: if one just throws all the ingredients into a bowl and throws it in the oven, the cake won't be good. So for the normal perspective, your process of manufacture is at least as important as the materials and ratios you use.

Keep it simplest, steady your process, and good luck.

Cheers,

Lussh

Thx for your time. It seems I have to elaborate some.

​I am doing this with some students at an art academy. I am using synthetic mid-quality ultramarine (I think it's from Kremer) and Lukas pure bleached linseed oil. We do this on glass plates with a 150 grain and have glass​​ mullers.

I have done this multiple times, but each time this colour goes bad.

Time of gringing doesn't seem to be of importance. It happens as soon as student work with it, but one student has been grinding away for 3 days, and still it would be runny or too stiff. And like I said: when adding pigment, it turned even more runny an stringy.​

I use Al stearate because this is used in the pauntmaking industry to make paint shorter. Linseed with bees wax, the same: it is known to make paint shorter.

Other colours student make are doing fine. I use a professional grindometer to check, and of course the consitency should be good.

Could it be that perhaps this batch of ultramarine is particuraly difficult to make? Perhaps I should buy another batch.... 

Last resort may be my small three roll mill, that might do the trick, but it isn't as fun for the students, and cleaning is a bitch.

An oil paint company that sells its product as artist-grade possibly inadvertently had ​one of its recipes published. It was for an inorganic pigment that is not known to be difficult to prepare.

The recipe had the pigment and the stearate filler at a 50-50 ratio (1 part pigment to 1 part stearate, by weight).

In addition to the huge amount of stearate, it used a small amount of Ultrasil, a silica additive for rheology/stabilization.

Considering how much stabilizer was used for that recipe, a notoriously problematic pigment like ultramarine might need more!

— SRS