Ok, now this is just for the beauty of the raw pigments that I love so much…
Here is what you need: a muller, a glass or marble plate, pigments and linseed oil. (There are other oils like walnut oil or poppy seed oil, which is sometimes recommended for white or blue, since it is a bit less yellowing. However, it is very fat and takes ages to dry – if ever – on canvas…).
Put some pigment on the plate, push a little dell into it and pour some linseed oil on top. Then, depending on the quantity, either start premixing it a bit with a palette knife or directly start mulling it with firm pressure and circular motions – think of it as drawing an 8. Continue until the paint has an even texture – that’s it!
This sounds easy, doesn’t it? Well it is – to a certain extent. First of all, please be aware that some pigments are more or less toxic and put your safety first. If you do not want to stay clear completely from some of the gorgeous cadmiums for instance, then please wear gloves, eventually even a mask and do not eat, drink or smoke while making your paint.
Some other pigments are very volatile and hard to get “wet”, so you might be obliged to add a wetting agent and/or a lot of oil, making the consistency of your paint more troublesome.
Regarding conservation: you can keep your paint for a while either in empty tubes you fill yourself or in lidded jars. However, home-made paint does not last as long as industrial paint tubes in general, so it is better to use it quickly.
There are many brands of wonderful pigments (like Schmincke or Sennelier, just to name a few), but to me, the “pope of pigments” is Kremer Pigmente. These people know everything about historic pigments, binders, restoration techniques and so on…