[Marvin Mattelson]

The subject of mediums is very tricky as alluded to by Steven. Mediums cannot draw, paint or compose. The hand of the artist controlling the brush determines the outcome of the picture.

It's been recently confirmed through rigorous scientific testing that painters before the 18th century used nothing but linseed and walnut oils. No secret mediums were employed. As a result their paintings have fared far better against the ravages of time than did much of the works that followed.

There is a lot of controversy concerning Studio Products and the claims they make. Both pro and con. I would caution against blindly following what manufacturers claim to be THE answer since their prime motivation remains fiscal health.

The other thing I caution against is following rules that contain admonitions such as always and must . There is no right way to apply paint. Any artist that thinks their way of paint application is the only correct way, is mistaken. This is the one area where the individuality of the artist can manifest and helps distinguish inherent uniqueness.

Mediums serve many functions. They alter the drying time of paints (slower and faster). They also can change the consistency of the paint by making it more transparent, translucent, stickier and/or smoother flowing.

Some of what we call mediums are simply just oils added to the paint. Some are combinations of various additions to the oil such as varnishes, synthetic resins, solvents and just about anything else imaginable.

The choices of appropriate pigments can somewhat mitigate their need. For example flake white dries quickly and may not be the best choice to keep a painting open longer. (titanium dries far more slowly).

The idea of painting over a medium can be tricky resulting in a fatter layer. However judiciously rubbing a little oil into dry paint film will decrease the sinking in of darks and allow the paint a little more flow with less drag.

Certain applications such as glazing and scumbling require more medium since the paint needs to be veil-like for these to succeed. Anyone who says that it is wrong to have oil mixed in with the paint has never had the opportunity to create paintings like Bouguereau, who used scumbling to create his luminous flesh.

Keep in mind that too much medium in all of your layers will lead to a much weaker paint film.

The bottom line is figure out what you want to achieve, pick appropriate whites for your technique and keep the KISS philosophy in your mind at all times.

Good luck!