Grinding Colors and Making Oil Paint

[georgeoh]

Ultramarine Blue
Ultramarine blue pigment is one of the more difficult pigments to disperse in oil when trying to obtain a paste or buttery consistency. It gets either stringy, long or fluid in consistency. When adding oil to a small pile of the pigment on a grinding surface, at first it may not wet easily, then suddenly it becomes soft and fluid. I have found that if you have ultramarine color in this state, put it aside for a week in a closed can or wide mouth jar. Then bring it our once again and grind it further, adding a little more pigment to the mixture, if necessary, to develop a thick paste.

Genuine Vermilion and Cinnabar
The problem encountered when dispersing heavy inorganic pigments, such as vermilion, is separation from binder. To prevent this some manufacturers would add beeswax or stearates to the oil.

Cadmium Yellow
The proportions of mixing and grinding medium cadmium yellow in oil should be 74 percent by weight of dry pigment and 26 percent by weight of refined linseed oil. When using raw linseed oil, and under certain conditions, as, for instance, in the case of a very bulky yellow (it appears very fluffy), 30 percent of oil and 70 percent of pigment will produce a paste. Poppy seed or walnut oil may be substituted for linseed oil. In all cases, be sure and grind this mixture well to prevent separation while it is stored in the tube. It would not be too lengthy to grind this mixture continuously for an hour with a muller.

When you to want to make an "extended" cadmium yellow, 40 percent oil should still produce a paste that when thinned will provide good covering power. The extending material for cadmium yellow is principally barytes, although calcium carbonate (whiting or chalk), terra alba or bentonite may be used. A good formula for extending medium cadmium yellow to achieve a lighter tone is 30 percent by weight of medium cadmium yellow, 45 percent of blanc fixe and 25 percent of refined linseed oil.

A Word About Mullers and Grinding
I recommend getting the heaviest muller possible. Keep in mind that while grinding the aim is to achieve shear force, which requires lateral movement rather than downward pressure. The weight of the muller will help you grind without having to bear down on the muller. Use your strength to grind across the grinding surface rather than applying downward force.

Get in the practice of using a hard rubber or plastic spatula to scrape the surface and collect the paint into a pile. The iron in steel spatulas may react with certain pigments, such as sulfide pigments. You can always use a steel spatula for clean up.

Using Additives
generally, there is little need for additives, such as aluminum hydroxide or wax, unless you want to adjust the rheological properties of paint. Let me explain: What you are essentially doing when mixing powdered pigment with binder is punching many tiny holes into the fluid and then displacing some of the fluid with the pigment. A second operation is breaking up agglomerates and aggregates of pigment particles into discrete or basic particles. This requires an amazing amount of shear force to accomplish and this is precisely what the muller does on the grinding slab. It applies shear or tearing force to the pigment particles and vehicle in order to achieve a homogeneous mixture.

There is a third problem when it comes to dispersing pigments: overcoming the surface energy of particles. The greatest contribution to viscosity of any dispersion is due to the particular nature of the pigment. Particle size is also an important contributing factor. The smaller the particle size the more surface area and hence more energy to overcome in order to wet pigment particles. Conversely, the larger the particle size, the lower the surface area and the surface energy, and easier it is to wet. It is also less likely for larger primary particles to form new agglomerates. Consequently, larger particle-sized pigments exhibit lower viscosity and increased flow relative to their small particle-sized counterparts.

[georgeoh]

Grinding Ultramarine Blue
Native ultramarine blue, or lazurite (also known as lapis lazuli), many times lacks the brilliancy of the best artificial grades available today. We have found an exception to this rule in the premium lazurite from Chile offered by Natural Pigments.

In oil, native ultramarine or lazurite is more transparent, while the artificial pigment is more opaque and greater tinting power. The reason for this is that the native pigment typically contains calcite, which is transparent in oil. The native pigment can also be granular in texture and somewhat refractory in grinding. Natural Pigments lazurite from Chile is very pure and has the highest tinting strength of any native lapis lazuli. The average particle size of the native Chilean blue from Natural Pigments is 20 microns. While this is larger than the artificial product, which can be less than 5 microns, any smaller granularity in the native pigment would loose the unique quality of the native pigment, this quality being impurities, such as pyrite, which can glitter like stars in the paint.

To grind native ultramarine in oil it will be found that 60 percent by weight of oil to 40 percent of pigment is a good average to figure on, but as the specific gravity varies considerably these figures cannot to be relied upon as an absolute. For Natural Pigments lazurite from Chile, use 65 percent by weight of pigment to 35 percent of oil as a good starting point.

There is an incredible variety of artificial ultramarine blues on the market today and available in a large number of grades. There are two distinctive processes of preparing this pigment, one being known as sulfate ultramarine, the other as soda ultramarine, the latter having a violet undertone, the former leaning to a greenish tint. In either process, the constituents are nearly similar, comprising kaolin, sodium sulfate, sodium carbonate, sulfur, carbon, quartz and infusorial earth. Not all of these are used in one operation, if, for instance, quartz is used infusorial earth is omitted and vice versa.

Sulfate ultramarine blue may be recognized by its having a slightly greenish-blue undertone when ground in oil, while soda ultramarine blue has a violet-blue character. The better grades of soda ultramarine blue are preferred for tinting whites, because the whites are not so apt to become greenish.

For grinding ultramarine blue in oil, the one that has the strongest tinting power should be selected and the average mixing will require 67 percent by weight of pigment to 33 percent by weight of linseed oil. This ratio of pigment to oil is only a starting point, because each grade of ultramarine blue and the type of oil used will vary the amount of oil absorbed. Refined linseed oil is preferable to raw or boiled oil, as it will give the blue a clearer tone and appearance.

For an exceptional clear appearance and to prevent any greenish cast in the oil color, use refined walnut oil or poppy seed oil. Separation of oil and pigment can be avoided if the blue is ground in a mixture of 75 parts refined walnut oil or poppy seed oil and 25 parts of heat-bodied oil or stand oil, which will aid the drying time of the color; 65 parts by weight of ultramarine blue to 35 parts by weight of the oil mixture will be about the right proportion.

As noted above, ultramarine blue pigment is one of the more difficult pigments to disperse in oil when trying to obtain a paste or buttery consistency. It can become stringy or "long" or very fluid in consistency. When adding oil to a pile of the powder pigment on a grinding surface, at first it may not wet easily, forming a crumbly mass, then suddenly become soft and fluid. We have found that if you have ultramarine color in this state, put it aside for a week in a closed can or wide mouth jar. Then bring it our again and grind it further, adding a little more pigment to the mixture, if needed, to develop a thicker paste.

[georgeoh]

Genuine Vermilion and Cinnabar
For artists' grade color, use the best grade of vermilion known as Chinese, or high quality native cinnabar, both of these pigments are available from Natural Pigments. Vermilion is the name of the artificial pigment, while cinnabar is the designation of the native mineral, both of which are chemically red mercuric sulfide (II).

To grind vermilion or cinnabar, 86 parts by weight of the dry pigment to 14 parts by weight of linseed oil, walnut oil or poppy seed oil is about the right proportion for mixing. Due to the heavy specific gravity, the pigment separates from the oil in tubes and some have resorted to using wax with the oil to keep pigment and oil together in storage, and while this can be employed successfully, you may have trouble with the color on account of the presence of the wax. The drying of oil can be seriously impaired by wax. Stearates are also effective in preventing separation. A better and safer plan is to grind the pigment in part linseed oil, walnut oil or poppy seed oil and part heat-bodied linseed oil, such as is used in making lithographers' ink. The proportion of the two oils varies considerably depending upon the viscosity of the heat-bodied linseed oil. You can later thin this color with gum turpentine for easier brushing without impairing the gloss or life of the color.

[nick-50]

I am starting slowly to make my own paints, my last batch of white has turned out superbly using safflower oil. I take on board what you say as regards the muller, but I use a small muler, which is quite adequate I find.I think it may be worth mentioning that one of the greatest assets to mulling paint, is the surface tension of the muller in the actual pigment. If it is kept perfectly square and flat during the mulling proccess, the force that is acquired by surface tension alone, is enough I think to offset using a small as opposed to a large muller. It does all need practice as I found.
I am awaiting some cold pressed linseed oil,( German, kremer, very pale colour) and will attempt to wash this, to its best state of purity. This I will use certainly for my whites but also my earths and blues etc. I think it is the ultimate for oil paints, though other binders are more than satisfactory. Any comments on this are most welcome

[georgeoh]

...cold pressed linseed oil... I think it is the ultimate for oil paints, though other binders are more than satisfactory.

Why do you think cold-pressed linseed oil is the "ultimate" for oil paints?

[nick-50]

I infer from your question, you have other views to my own (prejudices, misconceptions?) on this. I started using old holland paints, after trying w&n, and did lot of reading especially this website, as to properties of the various brands, but I seem to find as many seem to do, that cold pressed linseed, gave a different handling quality to the paint, . I have mixed some loveley titanium white using safflower oil, so i agree, it is the painting that counts, but maybe there is some element of wanting to get the most out of ones materials. I suppose one may also ask, why do some use different mediums and such , and some very few.

[georgeoh]

I infer from your question, you have other views to my own (prejudices, misconceptions?) on this.

No misconceptions or prejudices about cold-pressed linseed oil. We have gained much experience in making paint using a wide range of pigments and variety of oils. We have noticed that there is a pervasive concept that cold-pressed linseed oil is the best to use for making one's own paint. Some cite different reasons with offering much rationalization. Others cite that it has greater pigment wettability than other oils due to the high acid content. The interesting thing is that almost none of the paint manufacturers use cold-pressed linseed oil to make paint. One would wonder if all the paint manufacturers are wrong and a small group of artists are correct. So why is this? There are a wide range of industrial linseed oils available to paint manufacturers that offer high acid content, yet have been suitably aged and refined to remove the “foots” or mucilage. There is very little color in these oils and they handle quite well on the brush. Whereas, raw cold-pressed linseed oil has a high acid content, it is very yellow and contains many impurities that must be removed.

[nick-50]

I am trying to get the bethough it needs patience. I would like to get the benfits of using cp linseed for my whites as well as my other pigments. I have heard and my limited exsperience has shown that cold pressed linseed has quite different characteristics from other binders. it has I believe a different more intense light refractivity, than say safflower. Maybe one can be too fussy over this subject when it is the actual painting that matters but i feel that when one is deeply involved with a painting, the paint, the medium, all aspects of it, become one with us, and one can be a bit obsessive about ones materials. Or am i, like the Jesuits of old, trying to count the angels on the head of a pin?

[georgeoh]

I have heard and my limited experience has shown that cold-pressed linseed has quite different characteristics from other binders. It has I believe a different more intense light refractivity, than say safflower.
What other binders have you compared it to? More intense light refractivity? I am not sure how you mean this in this context. If you are referring to the refractive index of cold-pressed linseed oil as compared to that of refined linseed oil or aged linseed oil, then there is almost no difference, none at least this is perceptible by the unaided eye. The difference between it and other drying oils is also small and would only make a difference with pigments that have very low refractive indexes, not most whites like lead white and titanium white.

[nick-50]

Thank you for putting me right on this, George, i must bear this in mind. perhaps i am victim of a fad, I don't know, but one thing, I am learning to think rather than just paint!

[georgeoh]

The point is that while the romantic appeal of refining your own raw, cold-pressed linseed oil and the excitement of seeing mucilage separate from solution may be overwhelmingly popular for some artists who also claim to get back to the roots of art (funny thing is that these same artists only use modern synthetic pigments with this homegrown oil), it is not necessarily achieving a superior paint binder. Refined linseed oil with medium acid content makes a superior paint, because it yellows less, forms tougher paint films and contains sufficient acid to wet even the most finely divided organic pigments.

[nick-50]

I think a good part of all this, is to want to create something for oneself, the satisfaction of the craft aspect of painting. Whilst it is easy to get something from a tube or bottle what greater satisfaction than to make that same thing oneself to high standards, like baking bread maybe. The craft aspect may not appeal to some, but perhaps some of us are chasing something elusive that may reign partly or wholly in the mind, some holy grail or some alchemical recipe that will, add some magic to ones work. I can say this of myself to some degree, if that is a criticism I accept it. I have perhaps said enough of this subject.
May i say your discussion above on grinding colours is most worthy and useful.

[Dharma_bum]

George---What oil do you recommend for a beginer at paint making? Do you find cetrain pigments do better in one oil than another? Do you have a source you particularly like? I didn't see oil available on your site, did I miss it?

Dan

[georgeoh]

I think a good part of all this, is to want to create something for oneself, the satisfaction of the craft aspect of painting.
There is no doubt about the benefit of creating something yourself. In fact, that is what we encourage artists to do, and Natural Pigments provides not only the tools and materials to do so, but also the information. However, there is a lot of misinformation and so we encourage artists to arm themselves with good information that will benefit them. We hear many artists shake the magic rattle of certain mediums and oils—raw, cold-pressed linseed oil, being one of them. We recommend artists to try CP linseed oil, but there is no need particular benefit to using it over refined linseed oil.


What oil do you recommend for a beginner at paint making? Do you find certain pigments do better in one oil than another? Do you have a source you particularly like? I didn't see oil available on your site, did I miss it?
Dan, it is strange to us that most artists' materials manufacturers use terms to describe oil mediums that have not been in use by industry for nearly a century. For example, manufacturers of linseed oil products today do not use terms, such as stand oil. In fact, in a conversation with a research scientist at ADM (one of the world's largest producers of linseed oil products) the other day, he did not know what stand oil was. Only after I described it as highly viscous, heat-bodied oil did he understand what it was. This shows us that artists' materials manufacturers continue to avoid educating artists' on things that they themselves must understand in order to make modern colors.

So, what do we recommend for making oil colors? It depends upon the pigments, but as a starting point, we recommend special aged linseed oil, available from ADM and Cargill. Unfortunately, these companies cannot small quantities of these products to artists. At present, Natural Pigments only sells mediums and oils from other manufacturers, such as Gamblin, who still labels such viscous oil products as stand oil. However, by the end of March we will offer a range of oils, such as special aged oil, heat-bodied oils, and conjunctive oils from these companies under our label, but with complete specifications and guidance to choose what is best for different pigments.

[georgeoh]

How much hand grinding is needed to form satisfactory pigment dispersions in drying oil vehicle? Moreover, how can you tell when sufficient grinding has been done? The answers to these questions are not simple to provide and depend upon the pigment and vehicle selected for hand grinding. However, I can provide some general guidelines that may help artists in this task:

When adding oil to the pile of dry powder pigment on the stone slab or glass plate, do so drop wise (drop-by-drop), mixing the oil with a spatula or palette knife, until all the pigment powder is incorporated and the mixture has a stiff, dough-like consistency. DO NOT ADD MORE OIL TO THE MIXTURE AT THIS POINT. The mixture will appear too stiff for painting, but this is all right, because the stiff mass creates more shear forces as it is kneaded and, as the pigment particles are wetted, it will relax and become more plastic.

Knead this mixture for some time with the spatula or palette knife, carefully observing changes in the consistency of the mass. For most pigments, you should observe a slight yet noticeable change from a stiff consistency to one that is softer and plastic. Continue kneading the mass, as the change in consistency indicates that agglomerates of pigment particles are breaking down into smaller ones and more pigment particle surfaces are being presented for wetting by the vehicle.

If you do not notice any further change in the consistency of the mass, stop kneading it with the spatula or palette knife. Some pigments, such as ultramarine blue or lapis lazuli (natural ultramarine blue), are refractory and difficult to grind to the right consistency. The best approach to grinding such pigments is to knead the mass until no further change is observed in its consistency and then allow the mixture to "sweat." Sweating is a paint maker's term for allowing the pigment-vehicle mixture to stand for a period. Cover the mixture with a plastic film and let it stand overnight. Some pigment agglomerates simply require time to allow the air in their interstices to escape and for the vehicle to wet their surfaces.

If the well-kneaded mass has the consistency of stiff yet plastic paste (somewhere between dough and toothpaste), then you are ready to begin grinding the mixture with a muller. If the mixture is too stiff for grinding with the muller, then add more vehicle drop-by-drop. Knead the mixture between drops of oil to check the consistency of the mass. It typically takes only a few drops to turn a stiff dough-like mass into a runny liquid so caution in adding more vehicle is necessary.

Stiff paste is the best word to describe the consistency of the pigment-vehicle mixture that is best suited for hand grinding with the muller. It should be slight more stiff than you would use for painting. It will become more fluid as you grind, so avoid the temptation to add more vehicle at this point.

Gather the mixture into a pile at the center of the slab or plate and begin grinding with the muller in circular motions. Some may advise that you grind in figure-eight motions or other fancy gyrations. It makes little difference as long as you grind all of the mixture thoroughly.

Periodically, using the spatula or palette knife, gather the mixture back together at the center as you spread it around on the slab or plate when grinding.

As you grind the mixture, you will notice a distinct change in the consistency of the paint:


At first, pigment agglomerates will make small tracks in the mixture as you grind. You will see these begin to disappear entirely or at least become fewer in number. They may never disappear entirely, even if you grind from now until you wear a hole in the plate. Do not worry; you may never completely rid yourself of them and in themselves do not indicate a poor dispersion, because some may be large discrete particles of pigment and do not ruin the paint or decrease its brushability.


Initially, the paint should have a stiff paste-like consistency. As you grind with the muller, the paint will become more plastic and flowing. If it becomes runny and liquid, then you may have added too much oil. No problem, because you can add more pigment to the mixture. The only problem with adding more pigment at this stage is that it will increase the time needed to grind the paint.


The paint will usually have a dull mat surface before you grind. As the grinding proceeds, the surface of the paint will become glossy when you stop grinding and it is allowed to rest. This indicates that pigment particles are being wetted and are "sinking in" to the vehicle.


There will be a distinct change in the sounds emanating from the grinding. It may initially sound like sand grinding on the plate surface and then soften and become more quite. This alone does not indicate that the paint mass has been sufficiently ground and a good dispersion has been achieved. The reason is quite simple; some pigments never cause the sound of sand grinding while others never quite stop making this sound. It all depends on the hardness of the pigment being ground. Some mineral pigments are very hard, such as azurite, malachite and earth pigments containing a small amount of silica (sand). In any case, a distinct change in the sound should be noticed while you are grinding with the muller.


If after grinding for some time the consistency of the paint does not soften to the viscosity that you prefer for painting, then add more vehicle, but do so drop wise and check the consistency after every one or two drops.

After observing the four characteristics noted above while grinding and you do not notice further changes in them, you most likely have achieved the best dispersion possible with hand grinding. You can congratulate yourself for hard work accomplished.

[Marc Kingsland]

One has heard that certain pigments can be over mulled, with a resultant dulling of the colour.
The only way I can see this happening, is that if the pigment particles happened to be ground smaller.
Still what ever the cause, if there is any validity to this claim, which of the pigments should we take care to not injure?



Marc.

[georgeoh]

If a color becomes dull when grinding in a vehicle this may be due to some other cause, which I have not experienced.

There are some pigments that when ground finely lose their color saturation. These typically are vitreous crystalline pigments, such as azurite, malachite and dioptase. Azurite appears dark blue when coarse, but as it is ground more finely it becomes more and more pale. Other pigments change hue, such as cinnabar, which changes from scarlet red to orange red. However, when grinding the pigment in a vehicle with a muller on a stone slab or glass plate, this does not happen.

[Marc Kingsland]

Another reason just occurred to me.
Perhaps this claim is made by those who use metal rollers?

Marc.

[georgeoh]

There are warnings in painter's manuals about using iron spatulas or knives when mixing certain pigments, such as lead-tin yellow, but I have not encountered this problem with cold-steel rollers or even stainless steel spatulas and knives. Steel is the most common roll material on roller mills these days, so the warning would have been pervasive. I find many such warnings no longer applicable, because the materials have greatly changed within the last hundred years.

[kazucks]

I started down the road of making my own oil paint today, somewhat late after nearly 40 years of painting. I ground the Italian dark ochre and Luberon raw umber using refined linseed oil. I filled two large tubes of each and still have quite a bit left in the bag, so to speak.
I tried to use a small quantity of Lapis Lazuli that I inherited 30 microns it says on label, very light blue. I ground it quite a bit in linseed oil but it doesn't seem to want to combine. It is gritty and way too transparent, it doesn't seem like it combined, but I tubed it anyway for now. Is there some dark secret to making this into oil paint. The artist at the seminar at CAA recommended lapis be ground in casein.

[georgeoh]

I tried to use a small quantity of Lapis Lazuli that I inherited 30 microns it says on label, very light blue. I ground it quite a bit in linseed oil but it doesn't seem to want to combine. It is gritty and way too transparent, it doesn't seem like it combined, but I tubed it anyway for now. Is there some dark secret to making this into oil paint?The native mineral lazurite (lapis lazuli is the stone that contains the coloring principle of lazurite) and artificial ultramarine are refractory pigments and hence difficult to grind into paint. Here is what I wrote about it earlier in this thread:


Ultramarine blue pigment is one of the more difficult pigments to disperse in oil when trying to obtain a paste or buttery consistency. It gets either stringy, long or fluid in consistency. When adding oil to a small pile of the pigment on a grinding surface, at first, it may not wet easily, then suddenly it becomes soft and fluid. I have found that if you have ultramarine color in this state, put it aside for a week in a closed can or wide mouth jar. Then bring it our once again and grind it further, adding a little more pigment to the mixture, if necessary, to develop a thick paste.


Do not be surprised about the transparency of lapis lazuli in oil. Calcite is typically combined with lazurite to form the stone lapis lazuli, which when ground appears transparent in oil and hence adds to the normal transparency of the pigment. Artificial ultramarine is not as transparent as lazurite. Poorer grades of lapis lazuli contain larger proportions of calcite and hence will appear more transparent and duller in color.

The grittiness is the refractory nature of the pigment and improves to some degree by "sweating," which is a colorman's term for letting the pigment and oil mixture rest. Let it rest and regrind it.

Lazurite and ultramarine tends to make the paint long and soft, so if you do not like this consistency you can add a small amount of wax to the paint -- the amount of wax added is based on the consistency that you want.

[kazucks]

George,
Ok let me make it clear, I did read your above instructions concerning the procedures for grinding pigments. However, I do have some questions.

1. In grinding earth pigments, is it absolutely necessary to mix the pigments with a pallate knife or blade and let them rest overnight before grinding with muller?
2. When you are in the grinding with muller process, how long does it take for the grind, (quantity equal to one large tube) approximately?
3. What is the relative number of inches that you want to leave a large tube unfilled for crimping without the paint squirting out the top of the tube?
4. When grinding with muller, you are not really reducing pigment size or grittiness, you are just trying to fully integrate the oil into the pigment. Right?
5. Does the shelf life of the tubes that I am filling become less than commercially produced pigments or about equal?

[georgeoh]

1. In grinding earth pigments, is it absolutely necessary to mix the pigments with a pallate knife or blade and let them rest overnight before grinding with muller?No, it is isn't necessary for all natural mineral and historical pigments. Most earth pigments, for example ochre, siena and umber, are easy to grind and make a smooth paste without "sweating."



2. When you are in the grinding with muller process, how long does it take for the grind, (quantity equal to one large tube) approximately?That depends on the pigment and the type of oil you are using. I grind until I see a smooth paste, but some pigments will not create an absolutely smooth paste, so I grind until I see little change or improvement in the consistency of the paste. This may require only 20 minutes, perhaps an hour or more.



3. What is the relative number of inches that you want to leave a large tube unfilled for crimping without the paint squirting out the top of the tube?That depends upon how many crimps you give the tube and the size of the tube. I generally give a collapsible metal tube three crimps, which means you need to allow at least an inch to an inch and a half of space at the end for a tube with a 40-50 ml capacity. BTW, I am completing a concise manual on making oil paint, which I will send to you next week.



4. When grinding with muller, you are not really reducing pigment size or grittiness, you are just trying to fully integrate the oil into the pigment. Right?That is correct. You are dispersing the pigment particles in oil by breaking up the agglomerates of particles, presenting more pigment surface area to the vehicle and wetting that area with the vehicle.



5. Does the shelf life of the tubes that I am filling become less than commercially produced pigments or about equal?In theory, the shelf life will generally be less because the degree of dispersion is less than mechanically ground paints and especially paint that incorporates dispersing agents and stabilizers.

[kazucks]

George,
I have made 4 tubes of your Italian Dark Ochre, 2 tubes yellow ochre deep, 3 tubes of Luberon Burnt Sienna and 2 tubes of Luberon Raw Umber and have begun to use them already. They are really, really fun to use. I made them to the relative stiffness that I want and the handling properties are great. The paint is very dense and pigmented, the colors are just exquisite.
This formulating paint business is great, I am using them on a portrait now and they really handle much better than some of the brands that I have been using. This activity is not only fun but very rewarding.

[georgeoh]

I made them to the relative stiffness that I want and the handling properties are great. The paint is very dense and pigmented, the colors are just exquisite.I am glad you are finding the joys of paint making. I suspect you will discover, if you have not already, that being able to control the consistency of paint without the addition of mediums is part of the so-called secret of the Old Masters. Although higher dispersions is great for long term paint storage, lower dispersion rates do not adversely affect the paint film.

[Einion]

Other pigments change hue, such as cinnabar, which changes from scarlet red to orange red.
Just a quick check on this part, I've seen cinnabar being extracted by Kremer on a documentary and the hue moved towards crimson as the grind got finer, not the other way around. Different versions of the pigment maybe?

Einion

[georgeoh]

...I've seen cinnabar being extracted by Kremer on a documentary and the hue moved towards crimson as the grind got finer, not the other way around. Different versions of the pigment maybe?I guess its possible although I've never seen cinnabar become more crimson with finer grinding. It is perhaps that your pigment contained more impurities to begin with, which I have noticed in a sample of cinnabarI obtained from Kremer Pigments, and the saturation improved with finer grinding.

[kazucks]

George,
I put in an order for more empty tubes. I am having a field day making and tubing paint. The 10 or so earth pigments that I ordered from you are really great. The handling properties of the hand ground paint is really exquisite. I am making it very pigmented with alot of body and it is a real joy to use. I am getting some wonderful effects using it that are sort of new to me. The viscosity of the paint is very enabling.
I know I am probably not encapsulating the pigment as well as retail paint makers are doing but you indicated that from a construction standpoint that it shouldn't be too much of a problem.
Prior to this, I had never made any paint. Are these joys criminal? Will the paint suddenly drop off the canvas from pure joy?
I don't know whether I would dare try anything other than earth pigments, it seems that additional additives might be a bit complex for a beginning paint maker.

[georgeoh]

I know I am probably not encapsulating the pigment as well as retail paint makers are doing but you indicated that from a construction standpoint that it shouldn't be too much of a problem.The dispersion rate should not pose a problem for artist painting, but will only result in some separation for paint stored for a period.

Prior to this, I had never made any paint. Are these joys criminal? Will the paint suddenly drop off the canvas from pure joy?Should not pose any problems.

I don't know whether I would dare try anything other than earth pigments, it seems that additional additives might be a bit complex for a beginning paint maker.I am not sure what additives you mean, but you will want to begin experimenting with inert fillers, such as chalk, glass, etc., which is something the Old Masters did.

[grannyb]

Hi George,Thank you for sharing all this wonderful info on making oil paints.I have made my own for several years now and have graduated to trying encaustics.I am finding it hard to integrate the
pigments with the damar and beeswax.They tend to separate on heating which the recipe I have requires.Do you have any 'secrets' to impart?

[georgeoh]

Hi George,Thank you for sharing all this wonderful info on making oil paints.I have made my own for several years now and have graduated to trying encaustics.I am finding it hard to integrate the
pigments with the damar and beeswax.They tend to separate on heating which the recipe I have requires.Do you have any 'secrets' to impart?You must grind the pigment in the molten damar-wax mixture. I recoomend purchasing an inexpensive electric flat iron griddle, heat up your damar-wax mixture in the griddle and then add the pigment to the mixture. Once it is completely incorporated, take a glass muller and grind the hot mixture. Grind until the mixture is smooth and free of lumps. Wear gloves to protect your hands from the heat.

[Smokin]

Ive been trying to find out more about including barytes, chalk, or aluminum hydroxide into some recipes with lil luck. Im hoping you can shed a lil light on these addative or maybe point me in the right direction to obtaining this info. I realize that trial and error and experimentation is part of making paints, but Im hoping that maybe a few "rules of thumb" will prevent me from making too much endisirable paints.

A few thoughts and questions are:
_What does chalk actually do, does it make transparent pigments opaque?
_Aluminum Hydroxide, I assume it thickens the paint and prevents oil seperation, but does it have a transparent quality to it making opaque pigments somewhat less opaque? Is this an ideal addative for transparent paints where one wants to modify the feel or flow to?
_I know its undesirable to add too much suport,filler, or whatever, but what exactly is too much. I know Im asking a relative question here, but I know 95% chalk is too much and would make crappy dull paint, but whats considered negligible amount and when does it start to get excessive?
_Wax? prevents oil seperation? makes thinks matt? and whats else?

[georgeoh]

What does chalk actually do, does it make transparent pigments opaque?In addition to increasing the opacity in some situations (see below), calcium carbonate can increase light scattering, thereby decreasing the color saturation of some pigments, increasing the transparency of others, improving the paint body, making a harder paint film, improving the resistance of paint film to hydrolysis and neutralizing free fatty acids in the paint or formed as the paint oxidizes. It is probably the best overall additive to paint and routinely adding a small amount can be beneficial to any color.



Aluminum Hydroxide, I assume it thickens the paint and prevents oil separation, but does it have a transparent quality to it making opaque pigments somewhat less opaque? Is this an ideal additive for transparent paints where one wants to modify the feel or flow to?It reduces the amount of pigment needed by thickening paint, can increase the transparency of some paint, remains inert (does not react with most other pigments), and can help to prevent oil-pigment separation.



I know it is undesirable to add too much support, filler or whatever, but what exactly is too much. I know I'm asking a relative question here, but I know 95% chalk is too much and would make crappy dull paint, but what is considered negligible amount and when does it start to get excessive?It depends on the desired results, the pigment and the filler. For example, it is common for paint manufacturers to add as much as twice the amount of filler to pigment (2:1) in white colors. This can actually improve the opacity of white paint (see below). There are no rules of thumb for all pigments, binders and fillers. There are some guides for specific situations, but you will have to ask those individually.



Wax? Prevents oil separation? Makes thinks [sic] matt? And what else?Wax helps to prevent oil separation during storage, adds shortness to paint body and slows drying.

Extenders or fillers, such as calcium carbonate and silica, are used two ways in white paint to improve opacity. The first is essentially to prevent overcrowding of the white pigment particles (such as titanium dioxide) by providing "spacers" between the pigment particles. For highly loaded pigment paint, this improves light scattering by allowing each white pigment particle to affect the light independently. This benefit is typically seen only when the PVC (Pigment Volume Concentration) is above 30%, which is the case in most artists' paint.

The second value of fillers in paint is dry flat hiding. This requires that the paint layer have pigment and extender loadings above the critical PVC. In this situation, the surface pigment and extender (such as calcium carbonate) are exposed to air due to insufficient binder to cover the entire surface. The pigment and filler have a much wider difference in refractive indices compared to air than the drying oil, improving opacity. In the case of calcium carbonate in oil paint, dry flat hiding increases the opacity effect by a factor of 7.

[Smokin]

Wow thank you so much, this helps so much!

My goals for making paints are many, but ultimatly its the ability to be able control the paints characteristics Im after while, maintaining a paint that would be considered high quiality (high pigment ratio/high tinting strenth/good intesity). My fear is Ill add too much chalk or aluminum hydroxide significantly reducing the paint's quality, especially since I have no idea what a good starting point is for any given pigment.

Maybe itll help if I talk about 2 specific pigments, Titanium white and raw umber. I mixed these with just llinseed oil and pigment (by volume not by wieght and just by guessing till the consistancy felt ok without things getting runny) The titanium white easily mixes into a wonderflu light fluffy constistancy, but once tubed seperation happens and after a while, its almost as if this paint melts or its consistancy cant be maintained. On the flip side the raw umber mixed into a more viscous consistancy, in a pile its wonderful, no real seperation, but its very gritty, not a bad thing, but when I go to brush it, its almost like im sweeping sand at times. Maybe I just didnt add enough oil, but the consistancy of the paint out of the tube seemed nice to me.

Anyway, I made a greyscale set combining the white and raw umber, as more umber was added to the white, the more stable and viscous it bacame, and vice versa with the umber. Value 5 (50% white + 50% Raw umber) is a paint with my favorite consistancy, not quite like white and not quite like he raw umber, just a happy middle. My question is whats the best way to get the white and umber more like that grey 5 I made off the bat? Any suggestions or tips?

[georgeoh]

The separation of the titanium white is due to pigment flocculation and the discrete particles re-agglomerating into larger aggregates. It must be ground very well and perhaps you can add a filler, like calcium carbonate to help prevent it from separating. You can add calcium carbonate in a ratio from 1:2 to 2:1 calcium carbonate to titanium white.

Most umbers will combine with oil well and remain in suspension. The grittiness can either be indicative of not enough grinding or else a coarse particle size. This is usually not a problem, since umber is often mixed with white and the grittiness is reduced or eliminated.

The best way for artists to achieve consistent mixtures of colors is to grind each color separately in oil then mix the pastes in measured amounts.