What Kind Of Support Is Needed For Painting In Oil?

This does not refer to a kind of help line or financial support! A support is what a painter puts paint on to. There are several alternatives available (excluding painting on walls and ceilings, which we shall not go into here), some of which are traditional, some developed much more recently.
Wood panels have been a common type of support for hundreds of years. Today, however, there are better alternatives available and types that are easier to use. The problems with wood are that the timber needs to be at least one inch thick, and even then, unless it is of very good quality (such as mahogany) and is well and properly dried and seasoned, it may warp or crack. Hence it generally needs to be cradled. Altogether, it is an expensive alternative.
Plywood is a very good support, providing it is not less than five ply (i.e. look at the edge and count the number of layers). The more plies the better. Mahogany faced plywood is good but expensive. Exterior grade plywood (usually available from DIY retailers) has its layers much more securely bonded together (marine ply even more so) and is thus less susceptible to warping or its layers coming unglued. Both sides will need to be sized twice.
Manufactured boards used as supports are commonly hardboard (although rather thin), chipboard (but A�” is better than thinner sheets, yet still has a tendency to crumble at the edges) and MDF. The latter has increased in popularity in recent years, has a good smooth surface and is quite rigid. MDF is especially good for larger paintings because of its rigidity.
Canvass has been used for centuries and is made from either linen or cotton. The former makes a finer support, is generally preferable, and stretches and paints better; but it is more expensive than cotton. Many newcomers to oil painting use cotton because of the price differential and because it is generally more easily available from retail stores selling artists materials. Canvass needs to be primed (see below) and framed but most art material shops carry canvass ready framed and primed. On the other hand, some artists prefer to buy their canvass by the roll and prime, stretch and frame it themselves.
Also available from many artists stores are canvass coverings glued onto thin boards and then primed. These are relatively low priced and very useful for a beginner to start out on.
Supports generally need to be primed and those bought from retailers will already have been primed by having been coated with paint known as a ground, which acts as a sealant. If a support is not primed, the oil in the paint will be absorbed by the support and leave the paint rather powdery. In addition, priming also provides a better surface for painting on. Some primers are oil based and in this case the support first needs at least two coats of size. Rabbitskin size should be used.
However, if you are priming your own support (as, for example, when using MDF) it is simpler to use an acrylic primer. Two or three coats are usually needed, but acrylic dries very quickly and it is made to adhere to untreated surfaces. This provides a good foundation for painting on and it leaves a “tooth”, which some artists like. But if you want a really smooth surface, it can be sanded down. The acrylic can be applied using brush, roller or sponge. The latter two may be more preferable in order to avoid lines in the ground.
It should be noted in passing that you should not apply acrylic over oil paint, but it is quite safe to apply oil paint over either an acrylic primer or even a coat of acrylic paint. In the latter respect, while many artists like to use a white background, one might sometimes find it advantageous to have a colour, either using one straight from the tube or mixing two (or even three) acrylic colours together. Such a surface will usually be dry in about an hour, so there is little time lost.
A beginner in oil painting clearly needs to be aware of the various kind of supports available and their relative benefits and drawbacks. However, the easiest way to get started is to buy a canvass support already stretched, attached to a timber frame and primed. This is the kind of support most frequently stocked by shops selling artists materials. Once some experience has been gained, it is always possible to investigate the possibility of doing some or all the preparatory work ones self.