This story explains the basics about using mediums in oil painting.
As a paint additive, mediums serve several different functions in oil painting. Adding a medium to paint can extend its volume as well as extending its drying time.
By changing the viscosity of paint, a medium also changes how the paint flows out onto the substrate. (Viscosity is the measure of friction as one layer of fluid moves over another. As the viscosity increases, the paint becomes thicker.)
Mediums are also used in creating glazes, which add transparent layers of color to a painting as well as imparting a luminescent quality to the paint.
As a paint additive, mediums serve several different functions in oil painting. Adding a medium to paint can extend its volume as well as extending its drying time.
By changing the viscosity of paint, a medium also changes how the paint flows out onto the substrate. (Viscosity is the measure of friction as one layer of fluid moves over another. As the viscosity increases, the paint becomes thicker.)
Mediums are also used in creating glazes, which add transparent layers of color to a painting as well as imparting a luminescent quality to the paint.
Three
key ingredients comprise most mediums for oil painting: oil, varnish and a
solvent. Mediums differ depending on the type of ingredients selected and the
proportions used. For example, while linseed stand oil is traditionally used in these
mixtures, other oils, such as poppy oil, are used in mediums.
The
traditional solvent for thinning oil paint and making mediums is turpentine. The pungent
odor bothers many artists. Personally, I love the smell. It smells of painting.
As an alternative solvent to turpentine, many painters have chosen mineral
spirits. It does not have the offensive odor
that turpentine does as well as being a safer solvent to use. The disadvantage of mineral spirits is that it will not
dissolve Damar varnish, whereas turpentine, which is more volatile, will.
Recipes
can also include various additives.One basic formula is to combine equal parts
of linseed stand oil, turpentine and Damar varnish. NOTE My story on the Fat Over Lean Rule provides recipes for fat and lean mediums.
You can also combine 50% linseed stand oil with 50% turpentine as a medium. (NOTE: When mixed half and half with turpentine, the old sign painting would use a boiled linseed oil/turpentine mixture to preserve wooden ladders, scaffolding and tool handles.) As alternatives to homemade mediums, you can, of course, use commercial products, such as Winsor & Newton Liquin.
You can also combine 50% linseed stand oil with 50% turpentine as a medium. (NOTE: When mixed half and half with turpentine, the old sign painting would use a boiled linseed oil/turpentine mixture to preserve wooden ladders, scaffolding and tool handles.) As alternatives to homemade mediums, you can, of course, use commercial products, such as Winsor & Newton Liquin.
Unless you are experienced in making mediums, it is a safe practice to use relatively equal amounts of solvent and oil. The reason is that if you use too much solvent, the oil, which is the binder of paint, will start to break down. On the other
hand, you don’t want to use too much oil. Excess oil can lead to wrinkling
paint.
The proportions of oil and solvent can vary somewhat. As
the amount of solvent to oil increases, the paint is said to be leaner.
Conversely, as the amount of oil increases in the formulation, the paint
becomes fatter. The rule of thumb in oil painting is that you paint “fat over
lean”. What that means is that you want to paint leaner, low viscosity mixtures
first. On top of those, you should paint the fatter, higher viscosity layers.
The reason is that the leaner initial layers will dry first. If you paint a
lean mixture on top of a fat one, the top layer will dry first. As the fatter
layer underneath it dries, it will contract and the top layer of paint will
crack. For more information about the Fat Over Lean Rule read my story on the topic.
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Hingst began his career 42 years ago in the graphic arts field creating and producing advertising and promotional materials for a large test equipment manufacturer. Working for offset printers, large format screen printers, vinyl film manufacturers, and application tape companies, his experience included estimating, production planning, purchasing and production art, as well as sales and marketing. In his capacity as a salesman, Hingst was recognized with numerous sales achievement awards.
Drawing on his experience in production and as graphics installation subcontractor, Hingst provided the industry with practical advice, publishing more than 150 articles for publications, such as Signs Canada, SignCraft, Signs of the Times, Screen Printing, Sign and Digital Graphics and Sign Builder Illustrated. He also posted more than 325 stories on his blog (hingstssignpost.blogspot.com). In 2007 Hingst’s book, Vinyl Sign Techniques, was published.
© 2015 Jim Hingst
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