Varnishing Paintings: Why, and How?

Is there any one art material that causes painters more grief than varnish? Varnishing oil and acrylic paintings is at best a tricky and often misunderstood process. This is because many artists consider it the final and permanent step to painting, which could alter the final result of the work if not done properly. In fact, proper varnish is made to be a removable layer to safeguard your work against the elements. No need to be afraid! Let’s discuss.

Why varnish your painting?

Most art conservators and materials manufacturers agree that varnishing oil or acrylic paintings serves two main purposes:

1. to protect the surface of the finished work from UV rays, dust, and other contaminants, and
2. to unify the surface of the work to an even gloss, satin, or matte finish.

As mentioned earlier, the main misconception about varnish is that it is a permanent final layer. In actuality, varnish is meant to be totally removable from your painting. It is employed to take the assault from atmospheric elements, dust, UV rays, and any other environmental factors while your original painting remains untouched underneath. If over time the varnish yellows, cracks, or loses clarity, it can be removed and reapplied. Though the actual process of removing varnish is much more in-depth, you can think of varnish like a pane of glass, protecting your artwork from the elements. In this way, it makes your artwork more archival.

So how do you apply varnish?

Firstly, varnish should not be applied to a painting until it is fully dry. When is that? It depends. This is one of the tricky aspects of varnishing. For oil paintings, most experts agree that you should wait anywhere between 3 to 12 months for the paint to fully oxidize. This of course also depends on the thickness of your paint. For acrylics, your work needs to be fully cured, though this is not as much of a waiting period. Again depending on the thickness of the paint, you should wait anywhere from a week to a month. When in doubt, play it safe: overestimate!

For acrylic paintings, it is recommended to apply an “isolation coat” between the finished painting and the varnish. This consists of a coat of clear acrylic medium evenly applied over the entire surface. The purpose of the isolation coat is to protect the acrylic painting underneath from chemicals which may later be used to remove varnish. While oil paintings naturally are not threatened by chemicals used to remove their varnishes, acrylic paintings can be. The isolation coat is used as a buffer to lessen the threat to the artwork.

When varnishing for the first time, using a new varnish, or varnishing a surface you’re not familiar with, it never hurts to run a test. You can even test out different types of varnish on a test painting of similar colour and texture to view the results before applying it to the actual work.

Varnishing paintings with a brush

The most thorough and practical tips and suggestions I have found are written by David Pyle and posted on the Windsor and Newton website:

1) Use a 1”- 4” flat wide, soft, tightly packed, varnishing brush (such as the Winsor & Newton Monarch glazing/varnishing brush).  Keep it clean and use it only for varnishing.

2) Place the work to be varnished flat on a table – do not varnish vertically.

3) Apply the varnish in 1-3 thin coats, rather than 1 thick coat. A thick coat will take longer to dry, may dry cloudy, drip or sag during application and has a greater chance of showing brush strokes when dry.

4) Thinned varnish is more susceptible to producing bubbles. Do not be vigorous in your application.

5) Apply in long even strokes to cover the surface top to bottom while moving from one side to the other. While working, inspect the varnish layer at all angles for bubbles. Even them out immediately.

6) Once you leave an area, do not go back over areas that you have done. If you do, you risk dragging partially dry resin into wet, which will dry cloudy over dark colors. If any areas were missed, allow to dry completely and re-varnish.

7) After varnishing, we recommend that the surface should be shielded from dust with a protective plastic film “tent”.

8) For a matte surface, apply the first layer(s) using gloss varnish.  Because multiple layers of matte varnish will cloud, only the final layer should consist of the Matte varnish.

Varnishing paintings with spray varnish

As well as the traditional varnishes applied with brush technique, many manufacturers now offer spray varnishes. Spray varnishes allow you to apply extremely thin coats, lessening the chances of brushstrokes, clouding, or an uneven surface. A few tips for using spray varnishes:

1. Safety first! Always varnish in a completely ventilated area. This means that you have to have airflow between two different sources. You should also wear a respiratory mask to protect yourself from breathing in the chemicals.
2. Hold your spray varnish about one foot from your painting, and sweep in an even manner back and forth, creating a thin coat.
3. Wait between coats as per the manufacturer’s instructions (usually 15 – 30 minutes).
4. Leave your varnish to fully dry before handling.

OK, so how do you remove varnish?

I won’t lie: varnish removal is not the easiest task. It is however a necessary process in keeping your painting archival through decades of environmental abuse. How you remove varnish depends on which varnish you choose, and each reputable manufacturer will supply you with specific instructions for successful removal. In general terms, removing a varnish involves using a specific chemical (ammonia, acetone, or other specialized products that manufacturers produce to sell alongside their varnish). Because manufacturers and products can differ wildly, it is best to follow the specific instructions provided. Depending on the value or concern you have for the artwork, it is also always an option to hire a professional art conservator to expertly remove and reapply your varnish.

You’ve convinced me. Now what varnish do I choose?

If you care about the longevity and archival qualities of your work, you should use a high-quality removable varnish. Remember, manufacturers who produce high quality products also provide ample literature and information for you about their product, as well as how to apply it and how to remove it. Have a look at some recommendations for quality varnishes below, then go forth and varnish your paintings.

Windsor & Newton

Gamblin Artist Colors

Golden Artist Colors