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Varnishing Oils and Acrylics: Should you and if so, how?

This month we are going to have a look at Varnishing. It is an intimidating area for many artists as many feel that are too many varnishes to choose from, that they may ruin their painting if they don't varnish properly and some even question whether varnishing is really necessary. Read on for all the answers...

Varnishing off a paintingWhy varnish?

The reason most people varnish oil paintings is to ‘lift' the colour. A gloss varnish in particular will increase depth of colour and enhance the picture. However, technically, the important function of a varnish is to protect the painting.

A successful picture is likely to be hung for a long time. Everyday dust and grime will settle on the surface just as it does on furniture in your lounge. If a painting is left unprotected, this dirt will embed itself into the picture surface, dulling the colour and obscuring details and it is not possible to clean a picture without removing some of the painting surface. If the painting is varnished then this grime adheres to the varnish and once the picture is too dirty to be seen clearly, the varnish can be removed and replaced, leaving the picture as good as new.

Varnishing acrylic paintings also helps to enhance colour depth and unify sheen as well as protect from dirt, dust and abrasion but it also has added benefits. Varnishing helps if there is any residual surface tackiness that can occur with acrylic paintings. The varnish can collect any dirt and dust, protecting the original painting surface.

Here are some points to note:

  • Varnishes are suitable for oils and acrylics because the paint films are relatively thick and separate from their supports. Gouache, watercolour and drawings should not be varnished because the varnish will be deeply absorbed by the paint and/or paper, becoming an integral part of the picture. When it discolours it will not be able to be removed.
  • Although as mentioned colour depth is enhanced by varnishing, this must not be confused with dullness from underbound paintings- if your oil painting is really dull, the colour seems to have ‘sunk' as it dries, then your ground is too absorbent (or you have over thinned with solvent). Don't varnish until you have ‘oiled out' using Artists' Painting Medium. Wipe the medium over the dry painting to replace the oil which has sunk into the ground. Do not leave excess oil on the surface and repeat if necessary until the surface has an even sheen. For your next painting, use a Winsor & Newton Canvas or board which has the right degree of absorbency to avoid this all too common problem.
  • Sometimes artists varnish to help stabilise surfaces with added texture or damaged layers. The varnish will help here but it won't be removable without damaging the work. If you have pictures like this, keep the varnished work behind glass to keep it clean and think about how to improve your technique for the future.
  • The safest way to keep a picture clean is behind glass because the surface will never have to have contact with the solvent and friction involved to remove and replace varnishes. Aesthetically however, framing oils and acrylics (with glass) is not commonly done. Varnish is therefore better than leaving the painting unprotected. If you are going to frame behind glass then make sure you use a spacer to keep the glass away from the surface of the picture.

Cross section of frame showing spacerCross section of frame showing spacer

Which Varnish?

Winsor & Newton Dammar VarnishThere are many varnishes to choose from and this is the cause of confusion felt by artists. Over time resins have changed, the newer ones of the 20th century are less yellow than the traditional Dammar and are also more readily removable.

But artists have a different take on time and materials compared to other professions and would not appreciate a manufacturer dictating what varnishes they should use simply because it is better technically.

Artists' choose varnishes for the sheen they provide and also if they were/are used by their favourite painters. So Dammar remains one of the most popular varnishes even though it has been superseded twice technically in the last 60 years. Let's have a look at the varnishes available and their benefits.

Firstly, it is important to note that Gloss varnishes are chosen because they give the brightest, deepest colours but you will have to suffer the impact of reflection. Matt varnishes avoid reflection problems but the colours will be duller. All the varnishes can be used on oil, alkyd, Artisan or acrylic paintings.

  • Dammar Varnish: the oldest liquid varnish, this gives a very high gloss. Winsor & Newton is the traditional 5lb cut if you want to use it for mediums (which we don't recommend but millions use it). Over the decades it will need strong solvents to remove it.
  • Artists' Gloss Varnish: This is the most popular varnish and gives a very high gloss. It too will need stronger solvents to remove it as time goes by.
  • Artists' Matt Varnish: This is also one of the most modern varnishes, remaining readily removable. It is the most popular matt varnish, giving a medium matt sheen.
  • Artists' Satin Varnish: This is our original formulation which needs warming before use. Its advantage however is that it is easier to achieve a flawless matt finish. It provides a lower matt than Artists' Matt.
  • Artisan Gloss, Matt or Satin Varnishes: These varnishes are formulated avoiding conventional solvents, ideal for communal studios or those needing to avoid hazardous solvents. They can be used on conventional as well as Artisan oil paintings.
  • Artists' Acrylic Gloss, Matt or Satin Varnishes: These varnishes are uniquely formulated to remain removable from acrylic paintings. The Gloss is lower than Conserv-Art Gloss and the Matt is dead matt. Satin is nearer Gloss than Matt.
  • Aerosol Artists' Gloss, Matt or Satin Varnishes: Aerosol varnishes are really useful for paintings with rough brushwork as a thinner layer can be applied. They are also preferred if you find applying with a brush more difficult.

How to Varnish

Varnishing a surface

1. You must wait until your painting is properly dry. If you varnish too early you may disturb the paint surface, the varnish may be absorbed into the painting making the painting removable or the varnish may crack.

2. Oils, including Artisan need a minimum drying time of 6 months for thin films, Grifin alkyds a minimum of 3 months and acrylics a minimum of a week for thin films. The use of Liquin mediums within the paint film will not lessen the drying time required to wait to varnish. Also note that Liquin should not be used as a varnish.

3. Modern varnishes are not as sensitive to atmospheric humidity as Dammar but it is still sensible to avoid varnishing in damp conditions.

4. It is particularly important to choose a dust free area, keep the windows and doors closed so dust doesn't settle in the wet resin.

5. Ensure the varnish is stirred well, particularly matt ones.

6. Choose a wide soft brush, the Monarch Glazing Brush is excellent.

7. Pour the varnish into a clean flat saucer or tin and load your brush. Wipe it on the side of the saucer so it is not dripping.

8. Lay the picture flat or slightly inclined. Draw the brush lightly over the picture horizontally at 45° degrees. Do not brush back over unless more varnish is needed to cover. Continue to work down the picture until it is completely coated.

9. Leave to dry 24 hours and if a second coat is required, apply at right angles to the first.

And finally... Picture varnishes are soft so do not lean varnished paintings together or they will stick. Do not wrap varnished paintings in bubble wrap or pick them up with your fingers on the varnish or you will get impressions showing in the varnish.

And avoid hanging pictures in bathrooms or kitchens, above radiators or open fires as they will certainly get dirty very, very quickly.