Varnishing Oil Paintings: Reasons Why You Need To Varnish An Oil Painting

A painter applying varnish to an oil painting

A painter applying varnish to an oil painting - Image by Andrew Tischler

How do varnishes help improve the longevity and quality of an oil painting? Do you need to varnish an oil painting? We will answer these questions in this article, including recommendations for the best varnishes to use for the different stages of oil painting should you get started on this creative journey.

Varnishing an oil painting is necessary to protect the painting from dust and UV rays, even out the sheen of the paint, and revive the colors of the painting. The wrong timing for varnishing can cause cracking and discoloration on the painting. 

Do oil paintings dry?

Oil paintings do not dry; instead, the oil paints cure by oxidation, where the oil reacts with oxygen and hardens. However, for the purpose of this article and to make it easier for beginners to understand, we will use the term dry. 

If you wait until the initial layers dry before adding new layers, it may take one day or up to two weeks. This depends on several factors, for the oil paints to be dry to touch, so you can add more layers. However, you can explore the alla prima blending technique, so you can work on your oil painting faster. 

When Not to Varnish Oil Paintings

When the painting is not fully dry

Do not apply a final varnish until the painting is fully dry, as it can result in cracking or discoloration of the oil painting. If you want to apply retouch varnish, wait until at least three months before the surface is dry.

The key to a successful drying process is maintaining heat and airflow while preventing the dust from accumulating. A good place for this type of dryer will be in an open-air enclosure, or if you have access to lots of window light from inside your home, then utilize it.

The type of oil paint pigments also affects the drying process. You may also try the tips we outlined in how to make your oil paints dry faster.

When the colors have sunk-in 

After some time, the oil painting may look dull. However, do not assume that it lacks varnish because if the colors have sunk, meaning the oil on the top layer has sunk to the layer underneath, applying varnish may ruin the painting instead of improving its look.

Thus, it is best to apply Thickened Linseed Oil diluted with mineral spirits on a 1:1 ratio to improve the look of the painting.

Also, prevent the sinking of the oils by adding an oil primer after two layers of universal or acrylic gesso.

When to Varnish Oil Paintings

When you want to protect the painting 

Oil paintings take months, some even years, to finish. However, you want to protect the painting from grime and dust.

To protect a part of the oil painting, or if you need to take a break from painting, you may apply a coat of retouch varnish.

When you want to even out the sheen

Even if you have been careful with how you primed your canvas and applied your paint on the canvas, you may still encounter a patchy finish on your paintings.

To solve this issue, apply even strokes of varnish on the surface of the painting. However, you can prevent patchiness on the painting by using paints and mediums that dry simultaneously.

When you want to address UV rays

Protect your oil paintings from UV rays with a long-lasting, synthetic varnish.

When you want to touch up the colors 

Some oil paints, especially those of inferior quality, may look dull and flat. Applying a layer of varnish will improve the colors of the painting.

What happens if I varnish too soon?

Prematurely varnishing your oil paintings may result in several issues which can ruin your painting's quality.

Cracking

Even when the top surface is dry to touch, the paint underneath your oil painting continues to cure. Thus, when you apply the final varnish before the oil paint dries, the surface may crack.

You may observe hairline cracks on your oil paintings, and they can progress to bigger cracks, resulting in the loss of paint underneath the cracked surface.

Discoloration

Varnishing before the painting is fully dry may cause irreversible discoloration of your painting. The mediums you use for the painting may also result in discoloration. However, this type of discoloration is reversible with exposure to sunlight.

Which is the best varnish to use?

Different types of varnishes for oil paintings

We can use the following traditional varnishes for your oil paintings. Aside from the type of gloss, you can also choose from liquid or spray form.

Dammar varnish

Dammar varnish is an excellent varnish to protect and retouch your oil paintings because the varnish remains transparent. It has enough elasticity to accommodate the movement of the oil paints after application, provides temporary and permanent protection, and gives a glossy finish to your oil paintings.

It is made from natural resins and is the most popular among traditional natural varnishes.

Gloss varnish

Artists use gloss varnish, such as Winsor & Newton Varnishes, to improve the gloss of areas on the painting that has turned matte with time. Beware of very high gloss varnish as it glares when displayed under normal gallery light.

Matte varnish

On the other hand, matte varnish reduces the glare on the oil painting and is best for abstract and impressionist oil paintings. Matte varnishes are mostly available in spray varnish, like Grumbacher Matte Damar Varnish Spray.

However, matte surfaces look dull and don't look well on your oil paintings.

Satin varnish

Satin varnish is more desirable among artists because it has an excellent gloss without the dullness of matte varnish. You can mix matte and glossy varnish at a 1:1 ratio.

Synthetic varnish

Synthetic varnishes like Gamvar works like traditional dammar varnish. Apply all the varnishes in thin layers rather than one thick layer, as it can ruin your painting.

Varnish for water-mixable oil paints

You can choose from gloss, matte, or satin varnishes for water-mixable oil paints. These varnishes do not contain solvents, unlike conventional varnishes.

How to Prepare Your Painting for Varnishes

An art restorer preparing to work on an oil painting

Wait until the painting is dry

Apply varnish only when the painting is completely dry. An oil painting takes a very long time to dry, sometimes even years. Generally, oil paintings are dry to touch at six months, but the oil paints underneath are still wet. Wait until the one-year mark, though, before attempting to varnish your painting.

However, how do you know if the painting is dry enough for varnishing? To do this, run your thumb on the canvas. If something comes out like a thread, the painting is not dry enough. If it comes out chalky, though, the painting is ready for varnishing.

Clean your room and the oil painting

Clean your room before you apply varnish to your oil painting. Close the doors and windows to avoid further exposure to dust.

Clean the surface you want to apply with varnish. Wet a soft cloth, preferably lint-free, with a mixture of 20ml of ammonium hydroxide and 250ml of water and wipe it in small circles across the painting. Be sure to use your nitrile gloves before you work with ammonium hydroxide.

Choose the right varnish

Use a new and soft brush, wide enough to apply the varnish. Do not use this brush for other applications. Many artists recommend a satin finish rather than a glossy or matte finish.

If you need to apply varnish before the one-year mark for showing or delivering it to your client, use a retouch varnish. Apply it lightly to the painting.

Lay the painting on a flat table

Lay your painting on a flat surface because varnish tends to drip and thus damage the painting.

Apply in thin, uniform layers

Apply the varnish in three thin coats instead of applying in one thick coat, allowing the coats to dry first for 24 hours before applying the subsequent layers.

Protect your varnished painting

After the application of varnish, hold a "tent" over the painting. The tent is a plastic protective covering, such as a cling wrap, to prevent the dust from messing with the varnish on the oil painting. You can skip this step if you're sure that your studio is dust-free.

Varnishing Oil Paintings FAQ

How long will an oil painting last without varnish?

An oil painting needs varnishing after 3-6 months after you finish painting it. Retouch varnish protects paintings while waiting for them to fully dry before applying the final varnish in 12 months after adding the last oil paint. 

However, to be safe, we recommend waiting for 18 months, especially if you added some thick layers of paint in some areas of the painting. For impasto paintings, you need to wait a lot longer, probably up to two years or so. 

What does varnish do to a painting?

Varnish is a perfect way to protect your oil painting from dirt, moisture, and other damaging factors. Some varnishes are UV-resistant, so it protects your painting from discoloration from UV exposure.

Do I have to varnish a painting before selling it?

Yes. Artists recommend varnishing a painting before selling it as varnishing protects it from dust, grime, scratching, and moisture.

If your client for a commission wants the painting before the 12-month mark is up, apply retouching varnish first. Schedule final varnishing upon delivery so you can use it when the painting is ready.

Can I use linseed oil as varnish?

Linseed oil is a medium for oil paintings, but you cannot use it as a varnish.

Conclusion

The information in this article should help you understand how to best care for your oil paintings through varnishing. We hope that these recommendations provide an easy-to-follow guide through the process of varnishing your work and make caring for them more manageable. If at any point you hit a roadblock, please don't hesitate to get in touch and ask us a question.

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