Pettit 120 Brushing Thinner Pettit 120 Brushing Thinner is a general purpose thinner for thinning brushing enamels for easier application. Many paints when stored for some time before use will increase in viscosity and should be thinned with a good thinner for normal brush application. 120 Brushing Thinner evaporates at a moderate rate and is completely out of the paint film in several hours. Surfaces can also be washed with this thinner prior to preparation or painting to remove any contaminati