How you protect your paintings is just as important as how you prepare your painting surface, the quality of your paint, and what you mix with your paints while applying them. All of these tasks add up to not only how your final painting will look, but how it can be cleaned in the future — even decades from now. A finish coat of varnish, the right kind applied in the right way, ensures that your oil or acrylic painting will have an evenly distributed gloss, satin, or matte finish that won't yellow and will be protected from dirt, dust, and air contaminants like smoke. The varnishing process is an investment in the longevity of your painting.
When an oil or acrylic painting dries, the outer surface — the skin or film — hardens and actually separates from the inner paint substance itself. Depending on the mediums mixed with the paint during application, this outer surface dries with a matte, satin, or glossy finish. Typically, this finish is uneven and is a mixture of those different qualities. Varnish evens out this final surface quality to either a matte, or flat finish; satin; or glossy, more reflective surface. Giving your painting surface a uniform look makes it more appealing to the viewer by making it less challenging to the eye.
One word of caution: if areas of your painting have sunk and look dull, do not try to fix these areas with varnish. Use a good quality painting medium such as matte medium for acrylics or Liquin for oils to fill those areas. Let this dry completely before applying varnish.
The reason varnishing works well with oil and acrylic paintings is that once coated, over time the surface can become impregnated with contaminants like dust and dirt. Even wiping the surface to clean it is a temporary solution, important as it is to do this on occasion. But eventually, the surface can reach a point where wiping it off does little good and the varnish must be removed and new applied to revitalize the painting surface — and the painting!
Varnishes come in many brands and most are fine when used according to directions. Some better brands include Winsor & Newton, Grumbacher, Liquitex, Golden, M. Graham, Schmincke, and Gamblin.
The classic varnish used for centuries by artists dating back to the early Renaissance is copel, or amber. These were hard varnishes made from tree sap. They were a great protectant, but yellowed badly in time and became much more difficult to remove. A softer varnish used for many decades is damar (or dammar). Unlike copel or amber, damar and mastic varnishes are soft and dissolve in turpentine or mineral spirits allowing for easier removal and re-application. Even with the introduction of synthetic varnishes in the past decade, damar remains the most widely used by artists for their oil paintings.
Varnish can be applied by brush, the most common method, or by aerosol spray. Spraying requires even better ventilation than brush application. An appropriate varnish applied in the right way will give your final painting surface just the right appearance and can ensure proper maintenance of the painting for many years to come.
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