Three ways to use oil painting mediums

It is cer­tainly pos­si­ble to work with noth­ing but plain, unadul­ter­ated oil paint, but cer­tain effects are eas­ier to achieve with judi­cious appli­ca­tion of other mate­ri­als. These can include var­i­ous mix­tures of var­nishes, bal­sams, sol­vents, and thick­ened oils; such mix­tures are called medi­ums. Because all medi­ums weaken the final paint film some­what, they should be used in very small amounts.

Here are three ways to use mediums:

1. An oily or resinous medium can be mixed directly with paint. If so, it is best to use the small­est amount that will achieve the effect you are look­ing for—generally no more than 20% of total paint vol­ume, and pre­ferrably much less. Use a knife to mix a bit of medium thor­oughly into each blob of paint on your palette, or into what­ever mix­ture you want to have the prop­er­ties the medium imparts. Then paint nor­mally. A good medium will make the paint han­dle more smoothly. Artists have var­i­ous opin­ions about which medi­ums are best.

2. An oily or resinous medium can also be spread thinly onto the sur­face of the paint­ing before apply­ing paint (this is referred to as paint­ing into a “couch” of medium). Wipe with a cloth or rub it in with the palm of your hand to get it as thin as you can. Don’t apply medium to areas where you will not be paint­ing this ses­sion, since oil on the sur­face can even­tu­ally result in exces­sive yel­low­ing. The couch method has the effect of lubri­cat­ing the sur­face (which can make pre­cise detail work eas­ier) and reduc­ing “chat­ter” (i.e., drag­ging and streak­ing of paint strokes). It also improves adhe­sion between lay­ers, espe­cially if the medium con­tains a balsam.

3. If you use a thin medium con­tain­ing a high pro­por­tion of sol­vent, keep it in a small cov­ered con­tainer next to you as you paint. Dip your brush in medium and mix it into the paint on your palette just before you apply it. Don’t make the paint watery; use just enough medium to make the paint more work­able. Sol­vents can dis­solve a lower layer of paint if you haven’t given it time to dry com­pletely. Use sol­vents only if you have good ven­ti­la­tion and keep the medium con­tainer cov­ered when you are not using it in order to limit evaporation.

Now go forth and smear col­ored goo on flat surfaces!