Oiling out is a process which remedies a painting that has become dull; Artists’ Retouching Varnish also has a similar effect and we will look at both techniques here. First, oiling out is done with a recipe of 1-part Stand Oil to 4-parts Sansodor. Stand Oil is perfect for this because the heating process that it goes through results in a rich, non-yellowing, oil. You can make the recipe weaker or richer depending on the amount of Sansodor you use. If you have added oil to your paint already as you worked, you should use a richer mixture to observe the fat over lean rule. A painting becomes dull because either earlier layers have drawn the binder away from recent layers, or because the fat over lean rule was not observed. Using a soft brush to paint this mixture evenly across the surface will immediately improve the saturation and revive the painting. Remove the excess mixture with a lint-free cloth and you can paint again straightaway or wait for it to dry. Going forward though, you must only use the oiling out mixture with your paint and also make the mixture richer in successive layers as you go. Alternatively, Artists’ Retouching Varnish can be used as well but is best saved for a localized dull area. Whilst both techniques will bring a dull painting back to life, it is better to avoid the problem by observing the fat over lean rule at the start for a bright and even surface in your work.