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What are other kinds of paint made of?
I. Oil paint and Linseed oil. The binder of this technique is linseed oil. Now, what is the main characteristic of linseed oil by which we can understand it's "logic"? Unlike other vegetable oils such as canola or olive oil, linseed oil reacts with oxygen (a process called oxidation), to slowly go from liquid to gel to a tough solid form, therefore we refer to it as siccative oil because it solidifies through oxidation. Linseed oil is not the only siccative oil and therefore is not the only oil we could use, poppy seed, safflower or nut oil are semi-siccative oils, but, generally, we avoid using them as our "main" grinding oil because they will to dry slower and form less flexible paint film than linseed. Another important aspect besides the fact that linseed oil oxidizes rather than dries is that this oxidation doesn't stop when the paint is dry, but continues on for years after the painting has been painted, varnished and sold. So, the second important aspect of oil paint is that it is a dynamic technique in this respect that it still continues to transform (i.e. react, oxidize) when the painting has long been finished. Making oil paint The previous descriptions were Renaissance methods. An artist today might make their own oil paint with the following 21st century description:
The use of extenders in oil paints. Extenders or fillers have long been used in the making of oil paints. Though we might think of it as a negative thing, as adulteration, extenders do have a lot of virtues, and, if used in reasonable proportions they will allow economy and control over the painter's materials. Barium sulfate and alumina hydrate are the most common of "extenders" and are considered as white pigments: Pw21, Pw24. When adding any of those two pigments into your paint, you will obtain more quantity of paint, without affecting the color because they virtually have no tinting power. Here is a concrete example. We want to make cobalt blue oil paint and we decide to replace 1/4 of the amount of pigment with barium sulfate. What will happen is that without any significant color change, and still arriving with the same amount of paint in the end we will have saved close to 1/4 of whatever this paint would have cost to do without extenders because the price of barium sulfate in comparison with the price of cobalt blue is almost neglectible. So if you got a pound of any expensive pigment and systematically mixed it with extender in a 1:3 ratio, it is as if you had bought 1 pound and a quarter of that pigment, but that extra quarter only cost you neglectible amount of money. Of course economy isn't everything, we feel that the use of extender free oil paint, who's price of making it yourself is so low in comparison of the processed material, is well worth trying. Consistency of oil paint. When grinding dry pigments, you may realize that some colors will loose their consistency after a while. It is a normal phenomenon and in no way should a pigment be considered of low quality because of that. Ultramarine blue is the most stunning case of unstable consistency, when ground by itself and left to stand on the palette it will change from stiff oil paint paste to become liquidy and stringy. The solution to this problem is to add a stabilizer to the paint. Wax, and especially beeswax have long been used in the industry for this purpose, so we recommend that you do the same. Our experience is that a cold wax medium works very well for this purpose and is easier to incorporate in paint then raw wax. II. Acrylic paint The binder of acrylic paints is acrylic polymer emulsion. Unlike siccative oil that oxidize, this emulsion of plastic resins dries by evaporation of the water and solvents it contains to form a tough & flexible film. It can be purchased as gel or gloss medium, modeling paste and so on, each is acrylic polymer emulsion, but they have been added something else to make it mat or glossy, thick or liquid. One thing you have to pay attention is whether these mediums are designed to be opaque or transparent. Some acrylic mediums have been added either fillers or white pigments which makes them opaque, they can be used when an opaque paint is desired but attempting to glaze with such mediums would certainly be frustrating, if not impossible. Making acrylic paint Certainly, the easiest way to make good acrylics paints is by using dispersion of pigments. When making oil paint we have all the time needed to disperse the dry pigments plus the linseed vehicle, because of it's chemical nature, contributes to the dispersion of pigments. But with acrylic polymer emulsion, the available mixing time is very short and even when pre-mixing dry pigments in water and adding it to the acrylic, it is very difficult to obtain a paint that will be well dispersed and totally free of lumps. Dispersions, on the other hand, are pigments already dispersed to their fullest degree in water, therefore it mixes with acrylics in moments, eliminating the long and often unsatisfactory pre-mixing of pigments. III. Gouache and watercolor The binder for gouache and watercolor is gum arabic. which naturally comes from acacia trees. To make your watercolor we again recommend you to use the dispersions of pigments and it is most important in that technique. By adding drops of dispersions in the solution, you will instantly obtain transparent watercolor. To get an opaque gouache, simply mix either talc, zinc white or china clay into a paste using the same solution and add your dispersions or pigments. |
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