Grinding pigments and oil separation
 

Hi,

I recently dispersed (didn't really grind as it seemed to be fine powder already) some Red Oxide earth pigment in linseed oil, actually three different kinds of red oxides (from almost yellow ochre in color to indian red in color).

They seemed to require different amounts of oil to grind, which is probably normal as PR101 seems like the more varied of all pigments out there. Anyway, the one that required most oil to grind seems to show oil separation -- each day I find a big blob of oil when I open the tube (it is a mid-sized tube). I used absolutely nothing more than oil & pigment, just to keep it simple.

Anyone with more experience can give me some hints on how to avoid this? I tubed them right after grinding them, maybe I should have waited for a day or two for the paint to setup? Or is this an indication that the paint is not dispersed enough (it seemed alright with a drawdown) or that I am using too much oil (the other pigments used less oil but were of the same consistency when tubed)? Right now, I am just blotting the oil out before using the paint, maybe this separation is harmless..

Thanks in advance.

Check out sinopia.com - they suggest that the paint sit for a while.


This from amien.org's forum:
"If we find oil separating from the colorant in a tube of paint, we return the tube of paint to the seller; it's a sign of a ....paint that has not been allowed to rest in the factory before tubing."

Ramesh, welcome to the world of " Ye Olde Mastres" (pat. pend., all rights reserved). ! :)

Some background is in order. "Grinding" has always been a misnomer, as pigment stuffs have always had to be reduced to fine powder before they can be dispersed into oil by mulling.

In the days before manufactured tube colors, pigment stuffs were not micro-fine powders, as they are today, and the resulting paints were much "looser" than the tubed colors we have become accustomed to using through the last 150 years or so. This was largely due to the fact that vehicles cannot be dispersed as well by hand-mulling as in a 3-roll paint mill. Paints made with coarser pigment stuffs would have been necessarily more "lean", as it takes more oil to work smaller particles into paint - it's a question of the total surface area of the particles.

If you don't already own it, obtain a copy of Ralph Mayer's "Artists Handbook" which includes a table of useful standards for most common pigment stuffs, specifically, the oil absorptive indices of different pigments. Not all pigments absorb or react with vehicles(oil) in the same way, and many require additional amendments (e.g., stearates, waxes, clays, resins, siccatives, treated oils) in order to make useable paints.

The acid number of the linseed oil you are using is also a factor in the quality of paint that results, from its ability to wet and disperse into the pigments, to the nature of the paint films that it produces.

Most beginners mulling paint supply far too much oil, and nowhere near enough muscle. Making paint is hard, miserable work ! (that's why it was the entry level task for child-apprentices in the "good old days") It's also the reason it's nice to have some indication of how much oil any given pigment stuff is likely to absorb in order to be made into good paint.

A good way to proceed is to work as little oil into the pigment as possible, (using the oil absorptive index as a guideline) until you have what resembles clay too dry to "work". When your batch reaches homogeneity at this consistency, lay it by overnight (in a refrigerator is ideal) and mull it again. Ordinarily, you'll find it will reach a good consistency without adding any more oil after a second or third mulling.

The misinformation that tubes of paint that release free oil are "defective" has actually been published in major art magazines . . . by people who certainly should know better. Release of free oil is NOT a defect in paint, the fact is, a lot of "name brand" factory made paints are actually under-bound (i.e., not enough oil to form an adequately strong paint film). The remedy for "free oil" is to store the tubes up-ended, and of course, one may simply blot away excess oil by squeezing the paint onto paper towelling.

At the end of the day, you will learn much by making your own paint, but frankly, there is no particular advantage. In order to make paint not nearly as good as you can buy, you will certainly spend far more for materials and certainly a LOT more in time that's better spent perfecting your painting abilities.

Not even the old masters made their own paints once they rose above being apprentices! It's far better simply to procure the very best quality paints you can buy from reliable sources once you have learned the earmarks of excellent quality , as well as sub-standard paint.

The highest pigment loads, least percentage of fillers and amendments with the highest quality vehicles are not found in mid-tier, much less student grade paints (which are execrable!) and oftimes NOT by big "name brand" color-makers, but by the smaller, boutique colormen whose products are generally not found at massive discount in outfits like "Cheap Joe's" or "Jerry's Artarama" . . . conversely, the best economy is to buy the finest quality.

Without endorsing any specific maker, the following are examples of colormen whose knowledgeability and dedication to their craft (and to their customers) is noteworthy:
Robert Doak & Assocs., Williamsburg, Old Holland, Cennini, Michael Harding, Vasari, M.Graham . . .
to name but a few who come readily to mind. Doubtless there are a number of others, as well, if you search them out. Incidentally, most of these are sources who are willing to discuss the wherefore of paint making with you, much unlike the huge "name brands" who dominate the market in crafts-stores.

Thank you Richard and Julie for you responses, I have sufficient information now for the next round of paint-making.

I do realise I am never going to make as good paints as the name brand paint makers do, let alone boutique paint makers. I am mostly driven to learn new things and making paints is one of those.

As I learn to paint in oils, it seems like having a large amount of cheap paint helps me to try to get the right color mixture without worrying about how much paint I am wasting. So, making my own would let me reduce the cost without reducing the quality too much (actually, the paints I made last round already seem to handle nicer than the student-grade paints but this might just be wishful thinking justifying the hours put into each tube) -- plus I currently have more time on my hands than I am used to, so spending an afternoon mulling a couple of tubes of paint doesnt seem so bad.

I am looking forward to improving my painting skills enough to justify investing in professional paints..

Thanks again.

You're on solid ground, Ramesh. Any road, no one ever got rich by saving on paint. Having an abundance of materials at hand so that you can concentrate freely on your painting without scrimping, is definitely the right thing to do.

Hand-mulling paint is not exactly rocket-science. What you have just learned is that "real" paint, (i.e., all pigment, quality vehicle, no inert fillers) bears little resemblance to "student grade" colors, which would drive a master into frustration. Invariably, they entail questionable vehicles (safflower oil) and are largely inert fillers (clay, chalk and stearates) which are much, much cheaper than pigments.

Time is luxury, and using it to learn in depth about your materials will repay you very well in the long run. Good on ya !

I second Richard's words. Avoid low quality materials.