How to Varnish Oil Paintings
Not everyone chooses to varnish their oils. The benefits of applying a coat of varnish to an oil painting are to improve the appearance, unify the finish of a painting and get rid of ‘sunken-in’ areas. Varnish makes a painting easier to clean and provides a barrier to dust, pollutants, and physical damage.
Although varnish is essentially an easy and useful material to apply to your oil paintings, some pitfalls must be avoided. Below is a short summary of some steps you should take to avoid the common disappointing mistakes many artists have made. These comments are intended to provide useful information to our best ability, but are not to be considered complete and final instructions on varnishing paintings.
1. Read the labels regarding how to thin the varnish
Liquid varnishes in jars may be concentrated, requiring thinning, otherwise being too thick to be brushed on. Dilute them just enough (typically 15-20%) to obtain a brushable liquid. When it feels right on the brush, it’s ready to use.
Solvent-based varnishes cannot be thinned with one of the odourless solvents. These mild solvents are very good for other uses in the studio, but are too weak for thinning mediums and varnishes. Use only one of the full-strength mineral solvents or artist-grade turpentine (distilled or rectified). Even some solvents not labelled as odourless are actually too weak for this use and may cause milkiness or increase the thickness of the mixture. Test a small amount with the solvent for compatibility before diluting any quantity of your varnish. Golden MSA Varnish must be diluted with Solvent.
Thin only as much varnish as needed for the job, and do it just when needed. Any thinned matte or satin varnish not used up will tend to settle hard and become very difficult to re-stir.
2. Determine the shine level or glossiness.
If a matte or satin finish is desired and you wish to apply more than two coats of varnish (two coats are adequate in most cases), then the first coat or two should be gloss varnish. Matte or satin varnish should be used only for the final coats to avoid the possibility of a foggy appearance. Gloss varnish will not fog.
The following Golden solvent-based acrylic-resin varnishes are considered very good for oils (as well as acrylics):
3. Make Sure the Painting is Dry.
Do not varnish your oil paintings until the paint is fully dry. Oil paints require a long time to be fully dry, or cured, so to be safe, wait at least six months, or even a year. There have been many cases of oil paint being peeled or blistered by the turpentine, and this is usually attributed to the paint not being completely cured before being varnished. If the oil paint was applied very thickly, without driers, you might want to wait even longer.
4. Mix the Varnish Well.
A common mistake is failure to mix thoroughly matte and satin varnishes before applying. (Gloss varnish needs no mixing.) The result is a patchy or streaky finish. Matte and satin varnishes require thorough mixing. Avoid generating bubbles that may remain on the painting. Mixing should be done by stirring not by shaking. Be careful not to create bubbles either by shaking the varnish or by overworking it during application. Adequate prior thinning will help any bubbles to break and disappear.
5. Clean and Dry Environment is best.
Never apply varnish in a humid room as this may cause ‘bloom’, a foggy appearance. Be sure the room is clean, dry, and free of dust. Whenever possible, lay the newly-varnished work horizontally in a dust-free area to dry so that no runs occur.
6. Varnish is for a final layer only.
Do not paint over any varnish layer. Paints will not adhere well to most varnishes, and further, the paint layers will be lost if the varnish is to be removed for restoration.
7. This is probably the most important tip—
Make a test application on a material similar to the piece you have painted before you apply the varnish to your painting. This test panel should also be dry. In this way you can see just what the effect will be before you commit yourself. If a miscalculation is made, make it here.
8. Do Not Use Foam Brushes
Be certain that the brush or other tool you use to apply the varnish will hold up to such use. We know an artist who used a foam (sponge) brush to apply polymer varnish. The foam deteriorated during the application and left small particles imbedded in the varnish. On discovery the next day, the only remedy was to pains-takingly remove the entire film of varnish — a nasty job. A good bristle or soft natural hair brush is best. NB: On larger works such as a mural, a roller is also likely to cause bubbles.
9. Tips on the use of spray varnish For best results:
- Golden MSA Varnish is also available in a aerosol format
- Golden MSA Varnish must be diluted with Solvent.
- Spray over the work while it is horizontal.
- Start spray before the edge of the canvas, and stop after it, with the nozzle fully depressed.
- Apply two to three light coats, not one heavy coat.
- Work in a ventilated area as the spray is toxic.
- Spray with nozzle inverted to clear it when completed, to avoid clogging.
- Allow the work to dry standing vertically in warm clean area.
10. Follow Manufacturer’s Recommendations.
How to varnish an oil painting with Gamvar from Gamblin Artists Colors on Vimeo. Gamblin’s Gamvar is specifically designed by this company, which specializes in oil paint. This is an easy-to-use choice as you don’t have to wait several months before varnishing. It can be scrubbed on, thereby coating any areas of impasto.
Oiling Out from Gamblin Artists Colors on Vimeo.
Tips for Removing Varnish.
Kim Fjordbotten (June 2020) As owner of The Paint Spot, Kim Fjordbotten is passionate about helping artists use materials and make art. She is available as a speaker and educator for teachers and art associations. The Paint Spot offers exhibitions, workshops, and beautiful art materials to inspire your creativity.
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