It's also important to know about pigments so that the art is visually effective. In my recent paintings, I've limited myself to a palette of earth colors that works for me and I'm constantly learning about these pigments. There are a lot of things to consider, so it makes sense to limit your palette so you can get a handle on all the characteristics of your paints. I'm a rule breaker, so I need to know how far I can push things. In this post, I'll define the qualities of oil colors that affect the way paintings are made and how they look.
Color
The kind of pigment you are using affects many characteristics in your paint. The most obvious is the look of the color itself. Chemists have developed ways of categorizing both visual color and pigment chemistry, but the best way to determine the paint color is to get used to the paints that are for sale and look at your paintings under various lights. I make charts and color wheels. After you buy and use enough paints, you will have your favorites and you'll hope that they never go off the market.Color Names
You can't tell what you are using simply by reading the name a paint company gives a tube of paint. Two tubes with the same name might be made from different pigments. Or similar pigments can have two different names. Some paint colors are called hues, which means that they look something like the real thing but are cheaper. A Cobalt Blue Hue looks like a Cobalt Blue but doesn't contain cobalt.A lot of paints are no longer made the same way as the originals. So an Ultramarine Blue today might not be the same kind of Ultramarine people used a long time ago.
Color Sources
Paint pigments, today, come from two sources. There are natural pigments that are collected from nature and there are synthetic pigments that people make in a workshop or laboratory. Even the ancient Egyptians made synthetic pigments, so there's nothing wrong with them. Sometimes they are much better than natural alternatives.Pigment Types
There are also two basic types of pigment compounds. The first type is the organic pigment. These are carbon-based, meaning they are usually derived from plant or animal sources in nature or they are chemical dyes when synthesized by people. It's easy to confuse organic with natural. But, as in "organic chemistry," organic pigments are those that contain carbon. They can be natural or synthetic.The second type of pigment is an inorganic pigment. These are the earth or mineral pigments. Inorganic pigments can also be either natural or synthetic. They essentially contain metals such as cadmium, cobalt, manganese, aluminum, and iron.
Occasionally, the distinction between organic and inorganic might be unclear. For example, Sienna contains iron and also, as a clay earth pigment, contains decomposed plant matter. Another example is Graphite, which contains carbon but is considered a mineral. Maybe that explains why a graphite pencil falls between charcoal and silverpoint in character.
Particle Sizes
I prefer the way inorganic paints look. They have much larger particle sizes, usually, than organic paints and I think that makes a difference. Some of the synthetic organic pigments are so pure they look unnatural and garish. They seem to have a "chemical" look. If you glaze with an inorganic pigment that is roughly ground, you can even get a nice grainy look to the paint. I suspect that earth pigments are rougher on my brushes, though.Shade
One of the main characteristics of color is shade. Unless it is really neutral to your eye, each color has a bias toward one of its two surrounding hues on the color wheel. This undertone color is the reason you can buy, for example, an Ultramarine Blue (Red Shade) or an Ultramarine Blue (Green Shade).Temperature
Directly related to shade is temperature. It's a good idea to have a relatively warm and cool pigment choice for every hue. For example, you might have a red that is more magenta and a red that is more orange-red. If you have a cooler and warmer choice for each hue, then your mixing possibilities are better. Temperature is also very important for constructing lights and shadows.Value
Nothing is more important for rendering form than value. You have to step back from your canvas to note the relative lightness and darkness, or luminosity, of your paint colors. This is because your pupils will open up when you look at a violet and get smaller when you look at a yellow. So, to your eyes, everything becomes a middle value. In reality, however, when you step back, you will see that the violet is very dark and the yellow is very light. It is important to mix your colors on a grey palette instead of a bright white one, or you will have trouble seeing your values.Saturation
Saturation is the intensity or chroma of a color. Essentially, this means how vivid and bright it is. Some colors are intense. Some colors are dull, muted, and greyed. Some fall in between.Tinting Strength
When you are mixing your colors, you will find that each has a relatively stronger or weaker tinting strength. I have some reds that require only the tiniest dab of paint to significantly change another color I add it to. Tinting strength depends not only on the kind of pigment, but also on pigment load, which differs by brand; some brands mix a lot of oil with less pigment and charge less.Density
Density is the mass of the pigment. If you buy a tube of paint, it is measured in volume, but if you buy just the pigment with no binder, it may be measured in weight, instead. A denser pigment weighs more than a pigment with less mass in the same size tube. Pick up a lead white at the store and you will feel the difference (then put it back on the shelf and buy a nontoxic white). A tube of inorganic pigment will usually weigh more and may also be more opaque.Opacity
Opacity, or translucency, is the covering power of a paint when placed over another color. A paint may be very opaque, semi-opaque, semi-transparent, or transparent. Opacity and other characteristics can be affected by the pigment's density and particle size.Oil Content
In the process of creating a usable paint, some pigments require more oil than others. People sometimes use a measure of oil absorption to describe the amount of oil added to a pigment. Of all the characteristics, oil absorption seems to be the most vague in documentation online, even though oil is the essential property of oil paint. It might be easier to think of fat or lean paints in terms of oil content. This simply refers to how much vehicle is likely to be in the paint—the oil to pigment ratio out of the tube. Oil content doesn't necessarily relate to the thickness of the paint.Some oil paint has more oil in it and some has less. Though some manufacturers add more oil so they can save money, the amount of oil in the tube depends somewhat on the qualities of the pigment. Some pigment particles mix or suspend well in oil and others are difficult to combine with oil. I've found that some pigment and oil mixtures will change in viscosity when left to sit or when stirred. Also, some oil colors seem leggier than others: you can get long strokes, almost like lines of ink, with some pigments, while others prefer to work with shorter strokes.
Some paints require only a small amount of pigment to color the paint, and so require a higher ratio of oil. Some pigments are dense and soak up a lot of oil. Other pigments don't need as much oil to make a paint. Some pigments help the oil oxidize and dry, while others do not. Furthermore, oil itself can be fatter or leaner depending on the kind of oil. Manufacturers may also add inert ingredients like calcium carbonate as a thickener and binder, and this will affect the oil content in the tube.
As you paint, you will want to thin your paints with more solvent and less oil at first and then gradually increase the oil you add and decrease the solvent. How much of each you use depends upon the paint you are using. You can determine the oil content by working the paint with a palette knife or brush and getting a feel for fatter and leaner paint.
Utrecht makes a white that reminds me of printing ink. It's great for adding highlights in the last stages of a painting. This white contains titanium and zinc like other whites, but in using it, I found it to be way fatter than any of the other whites. So the fat and lean qualities of individual paints vary quite a bit by manufacturer. Oil content, along with characteristics of a pigment, affects workability, drying time, sheen, and the likelihood of the paint chipping and cracking.
Film
Without experimenting and doing more research, it's hard for me to say how the paint film is going to turn out in the long term. As a grad students, my cohorts and I have spent most of our time starting paintings. When we finish one, we usually turn it in still sticky. Even though I've done hundreds of oil paintings, I've yet to varnish any of them. As a result, we spend very little time studying the surfaces of finished work. In general, however, the dried paint can be hard or soft. It can be hard and then crack, or it can be soft and then crack depending on how flexible or brittle the paint is and what is under the paint. Or it can turn out just right.On a side-note, if you have to roll a painting, roll it with the paint side out. It's counter-intuitive, but the reason is that the paint stretches or contracts over time depending on how the painting is rolled, and you want to roll it so it heals back to normal when unrolled. If you roll the paint side in, then you will crack the paint when you unroll it to a larger surface area. The same concept goes for leaning a painting on board against a wall.
Aside from cracking, crazing, and chipping off, the paint film can yellow due to the content of linseed oil, and it can be spongy if you use a cheap oil that doesn't oxidize right. If you are desperate to get the paint to dry and it won't, even in the sun, you can resort to spraying it with Bullseye shellac every day for a week and the solvent may sink in and oxidize the paint all the way through. It's better to avoid this, however, since the paint may crack. With the right paints, your painting can be dry in several days.
Gloss
You may want to use some kind of varnish on your painting. Wait a number of months after the painting has dried. One reason for varnish is to protect the painting. Another is the fact that different paints dry to a different degree of gloss. Some paints dry shiny and glossy while others dry flat or matte. Gloss is also affected by the surface you paint on. I did a number of portraits directly on hardboard without any primer or gesso. My teachers would have been very annoyed if they knew, but I loved the way the oil soaked into the board. It gave me a drier, oil-pastel or egg-tempera look. And I loved the faster drying time and the fact that I could build up gloss as the paint got thicker.Drying Time
Some paints dry faster than others. Some of the organic reds take forever. I once threw away a study that still had reds that were as wet as the day I painted them a year-and-a-half earlier. I wasn't sure which brand of red I had used, but I had my suspicions and haven't used it since. Some pigments seem to stay wet a long time. On the other hand, some of my handmade earth paints are so dry, they are almost like pastels. You can dry your paints faster by putting the painting in the sunlight.Permanence
Once a painting is dry, most conservators and artists recommend getting it away from sunlight as it can fade the colors. Some pigments are lightfast but others are fugitive when exposed to light. Conservators can remove frames from old paintings and see how much the paintings have faded by comparing the paint hidden under the rabbet. But you can find ways to avoid this problem by using quality paints with excellent permanence ratings. Some organic pigments, particularly those that are plant-based, are very fugitive. On the other hand, my local museum has very, very old pieces painted with what looks like indigo but they don't look faded at all.Toxicity
As much as we take care of our paintings, we also have to take care of our health. No oils are nontoxic so artists need to always consider safety when working with painting materials such as solvents, mediums, and pigments. Use extra care with those labeled toxic, and avoid toxic chemicals altogether if you can. In the next post, I'll show how you can get a very large palette just out of earth pigments and iron oxides, which are all nontoxic.Aside from choosing safer solvents and paints, another good practice is to keep the turpentine covered and clean your brushes only when you are finished with a painting session, instead of cleaning every time you want a new color on the brush. With oils, you can wipe the excess paint off and go straight for another color without cleaning. The little bit of muddying that happens won't be really visible, but it will actually strengthen the painting by mixing the colors every so slightly. And you can start your cleaning with an oil or lactate instead of turpentine and finish your cleaning with a brush soap instead of going crazy with the turp.
Conclusion
As a graduate student in a very challenging painting program, I've found myself constantly studying the chemistry of paints and pigments to get a better handle on my tools. Some people say that inorganic pigments behave one way and organic pigments behave another way. In the end, it's more important to know what characteristics to look for in the paints on your own preferred palette. While settling on my favorite brands and colors, I've explored the eighteen qualities that I defined above, and I think that should give us a pretty good picture no matter what pigments we use.
