All paints are made with two basic components; a binder and a pigment.
A binder is an adhesive liquid that distinguishes one type of paint from another. A binder can be spread by brushing, spraying, knifing or any other means. When left, it will dry to a more or less continuous layer.
Pigments are coloured powders mixed into the binder to give it a specific colour.
A paint is made by mixing a quantity of pigment into a binder. When the paint is applied to a surface and left to dry, the pigment is locked into the binder, leaving a coloured mark. This is the most basic definition of how paint and painting works. There are infinite variations of paint application, layering, production etc. to be discovered from this simple starting point.
In addition to simply adhering the pigment to the surface of a painting, it is also possible for binders to perform other functions:
- If a binder is strong enough, it is possible to work it up to fairly substantial thickness. This is evident in oil and acrylic paint compared with watercolours or tempera. However, most binders perform better when applied in relatively thin films.
- Binders also have a visual effect on the pigment suspended within them. If you look at dry pigment compared to pigment in a binder you will notice that there is an intensification in the colour when the pigment made into a paint.
- The amount the colour intensifies depends on what binder it is suspended within. So Ultramarine oil paint looks more intense than Ultramarine watercolour paint. This is due to the relative transparency the binder. The more light that travels through the paint and reflects back, the less intense it will be. Oil is much less transparent than watercolour so it is a lot more intense.
Take a look at the image below to see the difference in colour intensity between dry Ultramarine pigment and Ultramarine oil paint.
These are the ideal requirements for any binder:
- Binders should not change colour as they age, as this will affect the colour of the pigments in them. Unfortunately, oil paints yellow and darken over age – if you take a look at the older paintings in a gallery, they are always noticeably darker than newer ones.
- Binders should not affect the colour of the pigment directly. This doesn’t happen often, but some acrylic binders will cause certain pigments to bleach (become lighter).
- Binders should stay structurally sound as they age, and resist cracking, peeling and flaking. The way that paint is applied combined with the conditions the painting is kept will also have a great impact on cracking and peeling over time.
- Once a binder is dried, it shouldn’t be easily dissolved by solvents. Watercolours and are particularly susceptible to damage if water is spilt or poured on them.
Types of Binders
- Cold-Pressed Linseed Oil
- Steam-Pressed Linseed Oil
- Safflower Oil
- Walnut Oil
Gum Arabic (Watercolour)
Emulsion (Egg Tempera)
Pigments are small particles of coloured material. The earliest types of pigments used in prehistoric times were found in the earth – minerals that had specific colours. Early artists also used charred wood and bones to make blacks.
From that point onwards, more complex pigments were produced from metal ores and chalk. The next development was to introduce vegetable and animal materials to expand the range of potential colours further.
In 1704 the first man made pigment, Prussian Blue, was produced, followed by numerous other man made colours. These became indispensable to modern and contemporary artists. Making much brighter colours affordable for use in artworks.
We usually group pigments into two categories; organic and inorganic:
- Earth colours, or natural mineral colours
- Processed natural mineral colours
- Synthetic mineral colours
- Animal-derived organics
- Vegetable-derived organics
- Synthetic organics
When using any pigment, it is important to be aware of its properties. Most binders are fairly consistent in texture regardless of pigment (such as acrylic and watercolour) but oil interacts with each pigment in a specific way
As a result, all genuine artist quality oil paints have unique qualities.
That is why It is important to avoid cheaper artist paints (particularly oils) as they are full of additives that make the paints more consistent with one another. This sounds good but in fact the addition of extra chemical often leads to incorrect mixing and problems with ageing. I would always recommend that you buy the highest quality oil paints you can afford straight away. It is better to limit the range of colours you use rather than buy lots of cheap alternative colours.
Pigment Properties That Apply to Oil
The following properties apply more to oil paints than other binders.
Different pigments require a different ratio of oil to powder to form a consistent paint. You will notice that some colours, such as Alizarin Crimson come out a tube in a very oily consistency whereas something like Viridian Green tends to be very dry. Cheaper manufacturers also tend to add an excessive amount of oil to their paints to cut down costs (as making a paint with a higher quantity of pigment is more expensive).
Certain pigments have a chemical effect on oil, causing it to dry much faster. Anything with Cobalt for instance, speeds up the drying time of the paint film. Whereas Titanium slows down drying time (so Titanium White dries very slowly).
Pigment Properties that Apply to all Binders
You will notice when painting in any medium, that certain colours are much more intense (saturated) than others. For instance, if you mix Cadmium Red with Yellow Ochre, are large amount of yellow will be transformed by a tiny amount of red. Whereas a tiny amount of yellow mixed into red will have barely any effect at all.
This is called tinting strength, and it’s very important that you are aware of the tinting strength of all the colours you use, either by experimenting with them or researching them online (or in a book). Otherwise there is a risk that you will ruin a large amount of paint by mixing it incorrectly, which will make your painting harder to complete and leave a big hole in your wallet.
Another property of all paints is lightfastness, which is the measure of how much a pigment will fade over time when exposed to light. For the sake of future generations admiring your work, it is important to be aware of how ‘permanent’ a colour is. Otherwise it will disappear from your lovely picture after a few hundred years (a lot shorter for watercolours).
The final property we will cover is the most important of all – toxicity. Many pigments used in painting are derived from heavy metals and as such are highly toxic. It is important to avoid handling paints with bare skin, inhaling pigment dust or ingesting paint. All of these acts will introduce hazardous elements into you body. Don’t worry too much though, it’s just a case of being careful when you paint and taking precautions.
Future lessons will cover how painting processes affect the ageing and appearance of a painting.