Read the whole information on this page for a thorough view on Impasto!!!
Before considering Impasto recipes, let us look at some pros and cons:
1 - IMPASTO EATS PAINT
Impastos may use a lot of expensive paint which increases the cost of producing an impasto work massively.
2 - IMPASTO WRINKLES OR CRACKS
Impastos tend to wrinkle or crack for reasons already explained in previously.
3 - WAX AND WAX + OIL MEDIUMS?
Impastos can be made by mixing your paint with bees wax mediums, but this will impart a very matt finish to the work which may not be desirable. Wax alone makes the picture matt and not only that, it can make it look quite dull too. This could be partially avoided by adding stand oil to the wax medium, bringing more elasticity to the paint film, but there is a serious downfall in this solution: In time, the paint film will yellow and also if mixed with highly fat oils such as Viridian or Alizarin Crimson and other Madder lakes, the paint film may be rendered unstable due to an uneven distribution of fat according to the fat-over-lean rule. Another problem with wax mediums is that wax picks dirt and dust which cling on to the paint film. Varnishing wax is not recommended either, for obvious reasons. If necessary to remove the varnish, the solvent will act on the wax making it go slightly softer and the paint film could be ruined.
4 - DESIRABLE PROPERTIES OF "SOUND" IMPASTO
Impasto should retain easily knife marks and be "energetic" in that sense, by adding a 3D element to a typical 2D work surface. It also should retain luminance and natural beauty of oil paint without excess gloss, but be able to reflect light effectively thus rendering the picture more luminous and bright. It should remain very hard but flexible to avoid cracking, it should "capture" light and return it to the viewer in order to show all the beauty of oil colours and the natural luminance of the picture.
5 - IDEAL IMPASTO MEDIUM
It should provide all the above in point 4 plus: Enable an easy transition from knife work to expressive brushwork without the need for a change of medium, but without clogging brush bristles, it should not yellow at all, even with light colours and whites.
Although wax pastes work well for impastos, the matt finish may not be the desired result, but it is true that bees wax imparts a very luminous effect and brilliance to oil paints, so its presence is somewhat desirable. The impasto should be flexible but dry rock hard while maintaining its flexibility.