How to choose between oils, acrylics, watercolours and pastels
One of the very first decisions you must make when you start painting is what sort of paint (also called medium) to use. The following information is intended to be informative and help you decide between the most commonly used paints.
What is paint and what is the difference between each type of paint?
The brief technical bit!
Paint is a dispersion of pigments, resins and fillers in a liquid carrier. By varying the basic ingredients the different types of paint can be created.
Oil paints as the name suggests contain oil. This is usually a natural vegetable oil such as linseed or a synthetic hydrocarbon made from oil.
The oil is the carrier used for the pigment and resins (alkyd). The pigments provide the colour which can be in the form of a soluble dye or an insoluble powder finely dispersed in the liquid. The various colours are produced from one or several pigments mixed together. By varying the different amounts, not only the different colours, but different shades and hues can be produced.
The resin is dissolved in the oil and acts as a binder for the different ingredients and to, and also binds the paint to the surface that it is applied to.
When the liquid evaporates after application, the resin and the pigments remain and form a skin which sticks to the painting surface.
Acrylic paints are similar in make-up to oil paints, i.e. they are similar in appearance and contain a liquid carrier, pigments and resin. However, the liquid used is water.
The resin is not the same type as in oil paints, because it has to combine with water. The acrylic resin does not dissolve in the water but forms an emulsion (forms globules). When the water evaporates the globules of resin stick together to form a skin. The pigments used must also combine with water and so are chemically different than oil pigments.
Watercolours consist of pigments, filler and water if they are in liquid form, or just pigment and filler in they are solid. As they have no resin component to bind the pigments and form a skin, they rely on the surface they are applied to, to be absorbent. A filler is a fine powder which can be used as a carrier for the pigment and provides texture/body.
Pastels are a solid paste form of water-colour. Far less water is used in their manufacture (when compared with liquid paints), and water soluble binders are used to maintain their solid paste form. Oil based pastels are similar with far less oil used than used in making oil paints.
What are the practical differences between the different types of paints?
dry slowly allowing time to work and to blend colours. The temperature of the air you are working in, and the proportion of thinner used dictates the drying time
can be used to produce texture by building layers
once dried sufficiently, can be over-painted without disturbing underlying layers
rich, deep colours which maintain their intensity when dry, so can be left unfinished and returned to later without a change of colour
can be used thickly or in thin, smooth washes increasing the scope for different painting techniques
colours are resistant to bleaching by sunlight and surfaces can be cleaned of dirt with methylated spirits
completely water proof and resistant to the elements
require brush cleaner/white spirits to clean brushes
usually applied to non absorbent surfaces including board, wood, coated paper and canvas
dry fast but still allows time to work and to blend colours. Can be a disadvantage when working with thick applications in hot environment
less viscous than oils so easier to mix but tend to produce less texture and brush strokes
can be mixed with water or other mediums/gels which are compatible with water
can be used thickly (impasto) like oils, or in thin washes, like waterclours, so can be used on both absorbent and non absorbent surfaces
once dried can be over-painted without disturbing underlying layers
water resistant when dry
colours dry darker than when applied so can give problems with colour matching if left
less resistant to sunlight that oils, surfaces can be cleaned of dirt with methylated spirits
requires water to clean brushes, but can give difficulty if brushes dry prior to washing
mixed with water giving transparent colour
dries fast and requires pre-wetting of the surface in hot environment
strong tendency to bleed so good for general wash techniques but can be difficult for fine definition
transparency makes it hard to rectify or hide mistakes
colours dry lighter than when applied so can give problems with colour matching if left
no white in watercolour painting, the white comes from the paper you are working on. So can be difficult to produce prominent white high-lights without preplanning or masking
paint can be lifted off by rewetting so can be useful in some techniques, but can be difficult to use in wet conditions or in hot/dry conditions where rewetting is necessary
brushes are cleaned easily with water and paint is reusable when dry by adding water
colour intensity is less when compared with other media and tends to bleach in direct sunlight. Problems with dis-colouration to the support and the media can occur in damp conditions
very difficult to clean the surface without damage so has to be protected from the elements under glass or other suitable material
colours are mixed on the paper/support by over-laying or blending so no drying time
easily used and require no brushes
oil based pastels can be thinned and blended with turpentine, or scrapped off to reveal colours underneath, known as sgraffito
a wide range of colour are available, however, usually a greater range of colours are required to create a picture when compared with other media
different brands and pigments tend to vary in softness so difficulties can arise when obtaining supplies from varying suppliers
soft pastel works tend to be liable to smudging and the colour coming off the support unless precautions such as fixatives or mounts are used to keep the surface away from frame glass
Watercolours are the cheapest to set yourself up with and most budding artists start this way. However, watercolour requires different techniques to other media and can restrict development
acrylics are not as expensive to buy as oils and can bridge the gap between oil and watercolour
oils are more expensive to buy initially; however a little goes a long way when painting thinly. Several paintings can be produced from a single tube of each of the base colours
Some people are put off by oil paints because of the solvents involved; they may be allergic to the solvents or may not want solvents lying around when young children are about. However, oil paints themselves usually contain linseed oil as the carrier which has low odour and is essentially non toxic. The pigments themselves are bound by the oil and are not available to cause hazards. White spirits and turpentine used as thinners or brush cleaners are flammable and should be used sparingly. However the volume used is very small and the hazards are many times less when compared with the use of domestic household paints. Saying this, low odour versions of paints are available.
Acrylics are the least hazardous as there are no solvents used and the pigments remain bound in the paint.
Can be hazardous if traditional pigments are used because they are not bound by resin and dry to a fine powder. However the quantities used are so small that hazards are very minimal.
Similar to watercolours, however soft pastels can produce a lot of dust so care should be take to minimise the amount you inhale. For example, do not blow on your work to remove loose pastel.
Your choice of paint
Choose whatever paint suits you. Try them out and you will soon discover whether you enjoy working with it and the results you get or not. If you like certain properties of different paints, you can try working with a mixture of paints (known as mixed media) in one painting. The variation is both challenging and rewarding.
The advice and information above is meant as guidance to the properties of the different paints. The only way you will know if you like a particular paint is to try it.