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 Glossary of Oil Painting Mediums Terms Adhesion is the force between unlike molecules, such as those of a wet paint film added over a drier layer or between the ground and an under painting. The under layer is partially dry ("closed") so the adhesive quality of the medium/paint mixture adheres wet layers one onto another to create a painting. Cohesion is the force between molecules of an oil painting medium/oil paint mixture that acts to unite them into a paint film. Dry time: time required for a layer of oil paints to dry sufficiently so another layer can be added. Evaporation rate (solvent): the rate at which the solvent in a paint and medium mixture evaporates into the air. Solvents like turpentine evaporate fast, solvents like Gamsol are much slower which greatly decreases your exposure to solvent vapors. Oil colors and the binder in the mediums do not start to dry until all the solvent has evaporated. Gloss level: the amount of light refractive from the surface. Wet oil paints have the same refractive index as dammar varnish. High gloss level makes colors look super saturated with great depth. Low gloss level makes a matte surface. Adding Cold Wax Medium mattes oil paints and mediums. Viscosity is the relative resistance of a fluid to stirring or movement. Oil colors from the tube are "viscous." Painting mediums can decrease or increase the viscosity of oil paints. Oil paint/oil painting mixtures have specific working properties that can be simplified by defining how mediums feel, most of which are either sticky or slippery. To make a medium that feels slippery, use an oil rich painting medium. Add solvent to reduce the "slippery" quality of linseed oil and increases its "adhesion." Using too much oil in painting mediums may cause paint films to wrinkle. Using too much solvent will inhibit the cohesive and adhesive properties. Mediums made with a high solvent content do not flow off the brush. To make a medium that feels sticky, use Galkyds or natural resin varnishes in the painting medium so that the first paint to touch the surface pulls the rest of the paint off the brush and increases its flow. |
