Art Supply Resources
Mediums & Varnishes
There is an overwhelming collection of little bottles filled with additives and fixatives available to change the behavior of your paints. Each will allow you to vary your paint in the most subtle or dramatic ways based on the substance. While you may be tempted to buy everything available, start with some basics and build your stock from there carefully. Learn to read and understand labels, and find out what your favorite artists use and duplicate their efforts.
Mediums are mixed with oil and acrylic paints to enhance the pigments’ behavior usually through manipulating flow. Separate mediums are used for oil-based paints and water-based paints.
For Oil Paint
Mediums for oil paints are made from mixtures of separate products with which an artist plays (often in capped bottles as shown below) to develop his/her own recipe. For example, a traditional medium mixture is one part Damar varnish, one part stand oil, five parts turpentine and a few drops cobalt or Japan drier. Mediums may also be bought in pre-made mixtures. Commercially made mediums can vary as much as home-spun recipes. Whether homemade or store-bought, mediums can be placed in a lidded glass jar and reused for many painting sessions.
Although acrylics can be thinned with water, they lose quality in the process. Mediums can aid in the flow of acrylics without changing the hue or intensity of the color. In fact, acrylics can be heavily manipulated with the bevy of new mediums now on the market. Gels will thicken acrylics for an impasto effect, retarders slow drying time, and tinting mediums alter hue and/or color intensity.
Generally, watercolors are mixed with water for creating transparencies, but mediums such as Gum of Arabic or even acrylic mediums can increase the brilliance of colors. There are also several different mediums available to increase the fluidity and texture of watercolors.
Varnishes Varnishes are solutions of natural or synthetic resins in solvents. For example, damar varnish is damar resin in turpentine. Shellac varnish is a solution of refined shellac in alcohol and wax varnish is beeswax in turpentine. When applied, the solvent evaporates and the resin dries to a solid transparent film. Varnishes can be used in a number of different ways with specific varnishes made to meet each requirement.
This varnish is layered over a finished painting to coat and protect it from dirt, dust and atmospheric impurities. It dries colorless and transparent, can be glossy or matte and some are removable.
This is a heavily thinned varnish with a lot of solvent and less resin. Oil paintings are often produced in layers with new layers applied on top of dried ones. When the paint dries, it tends to look more matte, in which case the paint added, even if it is the same hue or color, looks different even though it is not. This issue can be bothersome and can often hinder one’s color judgment. Retouch varnish is applied in thin layers in order to achieve the original wet-look when painting is resumed.
Varnish, most often damar, is regularly combined with mediums to thin oil paints before they are applied to canvas. In small amounts, it can make oils thinner, more manageable and more glossy. In large amounts, it can thin oils down to a glaze. Although it is possible to mix varnish alone with tubed paints, it is rarely done.
As you experiment with mediums, keep in mind these guidelines:
1) Use the minimum amount of medium to serve a particular purpose. Conservators seem to be in agreement that oil paintings done with straight paint (no mediums except a little thinner) form the strongest, most permanent films.
2) When using gobs of oil-containing gel mediums to build up texture, there is significant danger of yellowing.
3) Yellowing is sometimes rapid and pronounced when a painting is left in darkness; the yellowing will gradually lighten as the painting is exposed to normal daylight.
4) Mediums containing copal varnish are likely to darken significantly.
1)If you are new to varnishing, practice first on a test painting.
2) Glossy and matte varnishes are both available, and may be used independently or mixed to achieve the level of finish you desire.
3) Use a clean varnish brush two or three inches wide to reduce the chances of brush overlay marks. Try to cover in one or two long strokes, and avoid fussing with the varnish as it begins to set.
4) If you are using spray varnish, lean the painting at an angle against a wall and hold the spray nozzle at least twelve inches away. Keep the nozzle moving, and let each film dry before applying the next. Don‘t try to varnish too fast or the excess will end up running down your painting.
5) Always varnish a dry surface in a dry, dust-free environment. The slightest moisture will cause bloom–an unsightly whitish mess.