Priya Kapoor
The age-old advice for artists is to wait at least six months before varnishing oil paintings, but many artists resist this due to delivery deadlines. There are now modern synthetic varnishes that can be applied to touch-dry paintings, but the downside is that the varnish layer may crack as the paint dries and contracts. For thicker paintings, it is recommended to wait one to two months before varnishing. Acrylic paintings can be varnished within 24 hours, but an isolation coat must be applied first to unify the appearance of the painting.
| Characteristics | Values |
|---|---|
| Waiting time before varnishing | 6 months is the traditional waiting time, but modern synthetic varnishes allow for varnishing after a few weeks |
| Varnish type | Synthetic varnishes are advantageous over traditional natural varnishes as they do not yellow over time and are more flexible |
| Application technique | Use a flat, wide, soft, and tightly packed brush for varnishing, and apply in long, smooth strokes |
| Number of coats | Apply one thin coat of varnish, turning the painting 90 degrees to ensure even coverage; for higher gloss, apply a second thin coat after the first coat dries |
| Isolation coat | Required for acrylic paintings to unify the appearance and prevent streaking or blotching |
| Drying time | 24 hours between coats; shield the work from dust while it dries |
| Retouching varnish | A temporary gloss coat used for recently completed works, allowing continued painting |
| Spray varnish | Suitable for fragile surfaces or paintings with rough textures, as it helps avoid bubbles or pools of varnish |
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What You'll Learn
How long should you wait before varnishing a painting?
The time you should wait before varnishing a painting depends on the type of paint and varnish used.
Oil Paintings
For oil paintings, the traditional advice is to wait at least six months before varnishing. This is because oil paint takes a long time to dry, and varnishing too early can cause issues such as softening or degradation of the paint film, or cracking of the varnish layer as the paint continues to dry and contract. However, modern synthetic varnishes like Gamvar can be applied much sooner, typically within 2-3 weeks for thinly painted areas and 1-2 months for thicker textures. These varnishes use milder solvents that will not dissolve the paint film, even if it is not fully dry.
Acrylic Paintings
Acrylic paintings typically dry much faster than oil paintings, often within 24 hours. However, it is important to apply an isolation coat before varnishing to create an even sheen and prevent the varnish from soaking into the canvas or drying unevenly. The isolation coat should be applied with a gloss medium and allowed to dry before the final varnish is applied.
Techniques for Varnishing
Once the paint and varnish are dry, the varnishing process can begin. First, gently wipe the surface of the painting with a lint-free cloth to remove any dust. Then, pour the varnish into a clean, flat saucer or tin and load your brush. Be sure to use a wide, soft brush designed for varnishing, and avoid dripping by wiping the brush on the side of the saucer before applying to the painting. Use long, smooth brush strokes in one direction, turning the painting 90 degrees to ensure an even coating. Only one layer of varnish should be applied at a time, as multiple layers can result in a patchy finish. After varnishing, shield the painting from dust while it dries using a protective plastic cover.
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The fingernail test
The "Fingernail Test" is a method to determine whether a painting is ready to be varnished. It is a quick and convenient test that can be performed on the spot to evaluate the dryness of the paint. The test involves placing the end of the thumb on the test film and supporting the test panel with the forefinger. Maximum downward pressure (without twisting) is then applied to the film by the thumb. Afterward, the contacted area is lightly polished with a soft cloth. If the polishing operation removes any mark left by the thumb, the film is considered dry.
While the fingernail test is a practical way to test the dryness of a painting, it is important to note that it is a basic test and may not be entirely reliable. There are other tests, such as the pencil hardness test, that can be used in conjunction with the fingernail test for a more accurate evaluation. Additionally, the hardness of fingernails can vary from day to day, affecting the accuracy of the test.
It is generally recommended to wait at least six months before varnishing oil paintings to ensure that the paint is completely dry. However, modern synthetic varnishes allow artists to varnish their work after a few weeks. These varnishes enable the oxidation process to occur through a permeable layer, but the paint may not fully harden, resulting in a weaker bond between the layers.
When applying varnish, it is important to follow proper techniques. The surface of the painting should be gently wiped with a lint-free cloth to remove dust. The varnish should be stirred and poured into a clean, flat container. Using a soft, tightly packed varnishing brush, long and smooth brush strokes in one direction are used to cover the painting in a thin coat. Turning the painting 90 degrees, the same long strokes are applied across the wet first coat to ensure an even finish. Only one layer of varnish should be applied in this manner to avoid a patchy appearance.
After varnishing, the painting should be shielded from dust while it dries, using a protective cover. It is important to allow the varnish to dry completely before adding additional coats, typically waiting 24 hours between coats. Retouching varnish can be used as a temporary gloss coat on recently completed works, allowing for continued painting before applying a permanent varnish.
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Isolation coats
An isolation coat is a transparent layer between a finished painting and its varnish. It is not necessary for watercolour or oil paintings, but it is beneficial for acrylic paintings. This is because all acrylic polymer emulsions are dissolved and removed by the same chemical (ammonia), so without an isolation coat, the varnish removal process could damage the painting's surface.
The best method for applying an isolation coat depends on the painting's texture. For a textured painting, a thicker application is recommended (about 1.5-2.5mm). To eliminate brush strokes, apply the isolation coat evenly to the whole surface of the painting with a brush or knife, then softly roll over the wet coat with a damp Foam Rubber Brayer. For smooth paintings, a fluid or gel medium can be used.
GOLDEN Acrylics offers several gels that are suitable for isolation coats, including Clear Leveling Gel, Soft Gel Gloss, and Gloss UV Topcoat. Gloss mediums are recommended as they are the most crystal clear and least disruptive to the appearance of colours. When applying an isolation coat, only one coat of the isolation medium should be applied, and one should wait 24-72 hours before varnishing.
To make an isolation coat, one can use a mixture of two parts soft gel gloss to one part water. It is important to mix slowly and thoroughly so that no foam is generated in the mixture. The isolation coat can then be applied with a clean, wide, smooth brush that will not leave brushstroke lines.
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Varnishing techniques
Yes, a painting must be completely dry before it can be varnished. The drying time varies depending on the type of paint used. For oil paintings, it is recommended to wait for at least six months. To test if an oil painting is ready for varnishing, you can dip a cotton bud in Sansodor and gently rub it on an inconspicuous area. If no colour comes off on the cotton, you can proceed with varnishing. For acrylic paintings, it is suggested to wait for three to five days before applying varnish.
- Surface preparation: Before applying varnish, ensure that the painting surface is clean and free of dust, debris, or bugs. Use a lint-free cloth to gently wipe down the painting. It is also important to work in a well-ventilated area or wear a mask with air filters to avoid inhaling toxic fumes from the varnish.
- Choose the right varnish: Select a varnish that matches your desired finish, such as gloss, satin, or matte. Consider UV protection for added preservation. For oil paintings with uneven surfaces, a retouching varnish can be applied before the final coats.
- Application techniques: When using a brush, pour a small amount of varnish into a clean container. Load your brush, then wipe off any excess on the side of the container. Apply the varnish using long, smooth brush strokes in one direction. Avoid re-brushing areas that have started to dry, as this can cause streaks. For spray varnish, hold the can or sprayer 10-12 inches away from the painting and apply in steady, parallel passes.
- Isolation coat: Consider applying an isolation coat, especially for acrylic paintings. This coat isolates the paint from the topcoat of varnish and makes it easier to remove the varnish for cleaning without risking paint removal.
- Drying and additional coats: Allow each coat of varnish to dry completely before applying the next. The drying time may vary due to environmental factors such as humidity and temperature. Generally, it is recommended to wait at least 24 hours between coats.
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Pros and cons of matte vs gloss
It is generally advised to wait at least six months before varnishing oil paintings. This is to ensure that the painting is completely dry and to avoid potential issues such as softening or degradation of the paint film. However, modern synthetic varnishes allow artists to varnish their work after a few weeks. These varnishes enable the oxidation process to occur through a permeable layer, although there is a risk of the varnish cracking as the paint dries and the layers may not form a strong bond.
When choosing between a matte and gloss varnish, there are several pros and cons to consider.
Gloss Varnish
Pros:
- Deepens colour saturation and contrast, making colours appear more intense.
- Evens out sunken areas in the painting, creating a smooth and consistent surface.
- Achieves a "wet" look that some artists prefer.
- Retouching varnish, a temporary gloss coat, allows for continued painting and can be followed by a permanent varnish later.
Cons:
- Reflections from the gloss finish can create highlights that obscure certain parts of the painting, requiring viewers to adjust their viewing angle.
- Glossy surfaces are more difficult to light for display and photography due to the prominent reflections, especially with impasto style paintings.
- Gloss varnish may not be ideal for artists who want to reduce reflections and soften hard edges.
Matte Varnish
Pros:
- Significantly reduces reflections, making it easier for viewers to see the painting from different angles without glare.
- Evens out glossy and matte areas, creating a uniform appearance across the entire piece.
- Can be used to intentionally play with gloss and matte surfaces within the same artwork.
Cons:
- Overall contrast and colour intensity may be reduced, resulting in softer edges and a more subtle effect.
- Artists who prefer the depth and vibrancy of gloss varnish may find matte varnish less appealing.
Ultimately, the choice between matte and gloss varnish depends on the artist's aesthetic preferences and the specific effects they want to achieve in their work.
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Frequently asked questions
It is recommended to wait at least six months before varnishing oil paintings. However, modern synthetic varnishes can be applied after a few weeks. Gamvar, for example, can be applied when the painting is dry to the touch and firm in its thickest areas.
Varnishing too early can cause a long-term softening or degradation of the paint film, or it may simply extend the time the paint film is susceptible to damage. The varnish layer may also crack as the paint contracts while drying.
Applying an isolation coat is not necessary, but it can provide an even sheen and a glass-like surface, allowing the final varnish to glide on smoothly. It also helps to keep the varnish from sinking in or drying unevenly.
