Which medium is primarily used for glazing in paintings?

The medium primarily used for glazing in paintings is oils. Glazing involves applying a transparent layer of paint over a dried layer of paint to achieve depth and luminosity. Oil paints are particularly well-suited for this technique because of their slow drying time, which allows artists to work with multiple layers without the risk of disturbing underlying paint. The translucency of oil paint can create a rich, glowing effect that enhances the overall visual quality of the artwork.

In contrast, while watercolors can be layered to some extent, their transparency does not allow for the same depth of color and richness that oil glazes provide. Gouache, being an opaque medium, is not typically associated with glazing techniques because it does not allow underlying colors to show through. Acrylic paints can also be used for glazing, but they dry more quickly than oils, which can limit the ability to manipulate the layers effectively. Therefore, oils stand out as the most effective medium for glazing in painting.