Medium is the substance the pigment is mixed with to make he paint. This is what makes different types of painting and drawing materials different. It's also one reason the different painting and drawing materials are called ';media';. (Oil, acrylic, watercolour, guache, tempera, pastel, etc.)
Pigment is the material which gives the paint the colour. It is added to the paint medium as powder. In the case of oil paints, the medium is linseed oil. The medium binds the particles of pigment so they can be applied to the ';ground'; (painting surface) and adhere to it. (The meduium is often also called the ';binder';.) The linseed oil makes the particles of pigment appeart more luminous because it is more reflective, like glass, and alters the surface quality of each particle.
Turpentine is a thinner which dissolves linseed oil. It is used to clean paint off of brushes and other painting equipment, as well as the canvass when you wish to remove paint from it so you can repaint. Turpentine can also therefore be used (mised with ';painting medium'; - see below) to apply transparent ';washes'; to the canvas, as in watercolour or acrylic painting using water. Turps dres (evapourates) very quickly, so such washes will dry quickly also.
There are two kinds of turpentine you can use: ';mineral'; turpentine (the ordinary household kind) and ';pure'; or ';gum'; turps, which has a less offensive smell than ordinary turps (for most people).
Painting ';medium'; is a mixture of varnish, linseed oil and turpentine which is mixed with the paint before putting it on the canvas, It changes the consistency of the paint to make it spread more easily and further (paint is quite thick straight from the tube) and shortens the drying time. Varnish dries quicker than linseed oil, which takes months to dry. You add the amount which gives the consistency you require for a particular purpose. It dilutes the paint, so you can add enough to make anything between an opaque layer to a translucent glaze of colour (particularly the final glaze over the painting). You also vary the amount of medium to vary the drying time according to how long you wish to re-work areas on the painting (dry slower) or paint over previous layers (dry quicker). You can add more turps to the ';medium'; to do ';washes';.
There are different types of ';medium'; made of different ingredients (e.g. types of varnish). You can make your own ';medium'; by mixing damar varnish (available from hardware store), linseed oil and turps.
You can buy ';non-toxic'; mediums and thinners which work as well as the ordinary types, but are more expensive..
You also have to ';prime'; the bare canvas by painting over it with something. Commonly it is done with white acrylic house paint or ';gesso';. Gesso has to be sanded back and repainted in layers. It is prone to cracking, so is not ideal for use on canvas.
To ';tone'; the canvas, you can mix the acrylic with paint colour, so that the surface you begin with is not pure white. When you apply the primer, the canvas tightens on it's frame, because it is wet, and stays tight when dry. So if you are stretching your own canvas, don't stretch it too tightly, or it may tear when you ';prime'; it.
Pre-made canvases are usually already ';primed';, as is ';canvas paper'; (canvas glued to thick backing paper).What are Oil painting mediums?
well, thinners thin out oil paint, turp cleans and dilutes brushes, varnishes you put on the finished painting to give it sheen, luster, or shine. Sometimes you gesso a canvas before you start painting. There are all types of finishes for oil paintings, matte, high gloss, no gloss, protectants..ect.
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