Why Varnish?

January 26, 2017

The final step in a painter’s process is one of the most important: varnishing.

Much like the glass on a framed work on paper, varnish offers a removable protective surface that shields your paintings on canvas or panel from dirt, dust, scratching and UV rays. Without this shield, your painting is unprotected from the elements, which can both change the appearance of the work over time, and leave it open to damage.

To keep your artwork looking as good as the day it was completed, varnishing is an absolute must! However, it is also the step that is most intimidating as this protective layer has the potential to alter your artwork negatively if care in choice of materials and application method are not made paramount.

Below we’ve answered some of most common questions we’ve come across regarding varnishing. While some of the questions are geared towards varnishing an acrylic painting, most of the techniques and reasoning are applicable to other mediums too, such as oils.

In cases where the ideas are vastly different between mediums, we will specifically state the difference to help you better determine the correct information for your needs.

Overall, there are 3 main reasons why artists varnish their artwork:

  • Protection
  • Create an Even Sheen
  • Deepen or Saturate Colours

Varnishing your painting helps to ensure that it stays looking its best over the course of its lifetime. It offers a removable protective surface that protects the painting from dirt, dust, scratching, marring, and UV rays. For example, UV rays will eventually yellow the acrylic binder in acrylic paints and cause the pigments to fade. With a removable varnish layer, the varnish itself is the thing that yellows, and offers some protection to the pigments as well, helping to preserve the integrity of your art.

Varnish also offers a specific sheen to your painting. Depending on the type of varnish, you can deepen or saturate the colours of the painting, or soften them. This ability to create an even sheen helps to unify the artwork.

How long should I let my painting cure before varnishing?

Although acrylics dry quickly, you should wait at least a week before varnishing to ensure that the acrylics have dried all the way through. Even if it’s dry to the the touch, acrylics are often still wet underneath. If you varnish before the painting has fully dried the varnish can end up cloudy due to trapped moisture.

Traditional oil paint dries by oxidation, meaning the linseed oil and pigments react with oxygen and harden. This is why you shouldn’t varnish an oil painting until it has fully cured. If you varnish too soon the varnish won’t allow air through and will stop the oil paints from drying properly.

If you are varnishing an oil painting that has been thinly applied it can be fully cured within a couple months. However, larger pieces that have been painted with thicker applications can take from 6 months to as long as 2 years before it’s fully dried.

Glossy vs. Matte vs. Satin – Which varnish should I choose?

Artists generally choose varnishes for the sheen they provide and how they impact the colours of an artwork. When your painting has dried and cured, you may find that the different colours are varying levels of matte to glossy, often due to the different properties of individual pigments. Varnish can even this out, offering one unifying sheen.

Your varnish selection will also impact the colours. Gloss varnish is highly reflective and gives the brightest, deepest colours. The opposite is true of matte and satin varnishes, which reduces glare and can mute the colours, softening the look of a piece.

Any water–based polymer varnish with UVLS (Ultra Violet Light Stabilizers) is a good option for acrylics because you don’t need to thin it with a solvent prior to use. Matte and Gloss varnish can be mixed together to get a more specific look, however, we highly recommended testing this mix prior to varnishing the actual painting. Resin based varnishes can also be used on acrylics, however, it requires the necessary solvents for clean–up which not all artists have at their disposal.

Tip: Do you work in oils and acrylics? If so, then you only need to use one type of varnish because most synthetic and resin based varnishes work on multiple mediums.

The traditional method of varnishing an oil painting is to use dammar varnish, which is available in 2 forms — Dammar Varnish for the ending of the painting, and a thinner version that can be used throughout the painting process called Retouch Varnish. Both are made from dammar gum mixed with turpentine.

Dammar Varnish will provide the same unifying sheen that acrylic varnishes provide. It’s also more impermeable than acrylic varnish because some of them will soften in warm weather, making them slightly tacky.

Artists should note that dammar can yellow and will become brittle over time. Synthetic resin based varnish such as GOLDEN MSA Varnish or Gamblin GamVar is the best solution for overcoming this. Resin based varnishes contain UV light filters and stabilizers which help to decrease the chance of yellowing and embrittlement, while still having the traditional properties of dammar.

Retouch Varnish is commonly used to add gloss, thin, thicken, or increase the drying time of oils. It also makes the colours look wet again if a painting needs retouching after it has dried. Some artists will even use this as a temporary varnish layer if they have to take the painting out of their studio before it’s been properly varnished.

Can I mix different Varnishes together?

Some varnishes that are made by the same brand, such as Gamblin GamVar, can be mixed together, however, each varnish is designed to achieve different results. We highly recommend that you experiment with different mixtures on a sample piece that has been painted with the same materials and that has cured for a similar amount of time.

Can you Varnish Watercolours?

While some watercolourists do varnish their paintings, it’s important to note that the varnish that is applied will soak into the watercolour paper and become a permanent addition to the piece. It will change the appearance, texture and feel of the paper. The change in the surface could also re–categorize the watercolour as a mixed media piece.

While this is fine if you are using a variety of watermedia, the varnish layer could potentially exclude a watercolour painting from being considered one by some museums and conservators. If you do experiment with varnishing a watermedia piece, always use a solvent based varnish because the water in acrylic varnishes can re–wet the watercolour, potentially damaging the artwork.

What should I do before I varnish?

TESTING 1, 2, 3 –  before applying an isolation coat or varnish to finished artwork, always test your selected materials on a sample piece that has been painted with the same materials and that has cured for a similar amount of time. This is key to ensure these final finishes will enhance, not hurt, your artwork.

OUT, DAMNED SPOT –  It’s always best to varnish in a clean environment. If dust particles or lint were to fall onto the painting while the varnish dries, it may become a permanent addition to the piece. Some people recommend vacuuming prior if you have carpet, using a fan to circulate air, or to use a safe, protective cover.

STIRRED, NOT SHAKEN –  to avoid bubbles in your application, simply stir your medium or varnish prior to application. If the medium is shaken rather than stirred it will be bubbling before you know it, and these bubbles will cause an uneven varnish layer.

ON THE LEVEL –  always work on a level surface so your medium and varnish layers dry in an even coat. If you have to work vertically, it is recommended that you spray apply these layers to reduce dripping.

I SEE THE LIGHT –  photographing your artwork gives you a backup and reference of what the image looked like prior to varnishing, should things go sideways. Not only that, if you photograph a nice glossy painting, the camera’s flash will bounce right off and leave a flashy star right where the camera was.

You mentioned isolation coat — explain?

An isolation coat is a layer of acrylic gel or medium applied prior to varnishing an acrylic painting.

This non–removable coating sits between the painting and the varnish, physically separating the paint pigments from the varnish. When the time comes to clean the painting, the isolation coat will shield the work from the chemicals in the varnish remover. The isolation coat also seals any absorbent areas left on the painting, providing a smooth glass–like surface which allows for an even application of varnish.

Regardless of the sheen you have selected for your varnish layer, you’ll want to select a gloss acrylic medium to offer the clearest view to your work.

IMPORTANT: The isolation layer is crucial when applying a matte varnish over an absorbent surface to prevent a cloudy or “frosted” look from occurring. This frosted look happens when the varnish and solvent are absorbed into the support, leaving the matting agent exposed on the surface.

For brush application, the isolation coat can be made by diluting 1 part gloss acrylic medium with 1 part water. This ratio is largely dependent on how thick the gel medium is. If using GOLDEN Soft Gel (Gloss), GOLDEN recommends using a 2:1 ratio of acrylic gel to water.

For spray application, GOLDEN recommends a 2:1 mixture of GOLDEN GAC500 to GOLDEN Transparent Airbrush Extender. This can be applied with an airbrush or a touch–up spray unit.

The absorbency of the surface will generally determine the number of isolation layers required. For non–absorbent surfaces, 1 brush coat is recommended while 2 sprayed on coats are recommended. For more absorbent surfaces, it is recommended to apply the isolation coats until you achieve a satin sheen on the surface. This may require 2 or more brush applied coats or 3 or more spray applications.

An isolation coat should be left to dry for at least 24 hours prior to varnishing.

How–to Varnish. Should I brush or should I spray?

You can apply varnish either by spray or brush. Spray varnishes are useful for speeding up the varnishing process on paintings with rough brushwork or on mediums that shouldn’t be touched by application tools. Sprays must be used in a very well–ventilated area, which is a large factor as to why applying with a brush is the most common method. Brush–on varnish also has a thicker consistency that offers a rich look and allows you to achieve a deeper colour saturation — one that really makes the piece come alive!

Brush Application
The size of the artwork will largely determine the size of the varnish brush. A wide wash brush with high quality bristles (synthetic for acrylic, natural for oil) will give you the most control and smoother application. Use a shallow container and wet only the lower quarter of the bristles.

ACRYLIC: Try an Opus Legato, or for larger pieces, the Liquitex Freestyle Varnish Brush

OIL: Try the classic Escoda Flat Brush or a Winsor & Newton Artists’ Oil Brush

The technique for applying brush varnish is to start in the middle and work your way outwards. This will limit the amount of varnish that may creep off the edges during application. In the beginning, don’t focus on leaving brushstrokes, simply focus on achieving an even application.

Once the varnish has been applied to the entire surface, you can then even out the brush strokes by starting at the top and working your way down horizontally, slightly overlapping into still wet, adjacent sections. Avoid going back over a layer that has started to tack – up — this will make the finish uneven.

Brush gently, as overly aggressive brushing will cause acrylic varnish to foam up. If you are varnishing a bigger piece, it’s recommended that you either divide the painting into a grid, or follow the shapes in the painting.

Apply thin coats of varnish rather than one thick layer as it will take longer to cure and could become cloudy. You can apply 2 or 3 coats of gloss varnish, while matte or satin can be applied in no more than 2 coats.

Spray Application
The size of the surface to be sprayed will determine the best type of spray equipment to use. Artists generally use a spray from an aerosol can or airbrush.

Try to maintain a uniform distance from the surface by making straight passes across the work, changing direction once the spray has cleared the edge of the piece. Slightly overlap the spray pattern with each pass, until the entire piece has been covered. If you want a more even application, turn the painting 90 degrees to apply a layer that is perpendicular to the previous one.

Spray 3 to 4 light coats instead of one or two thicker applications.

How long does varnish take to dry?

When building up multiple layers of varnish on an acrylic painting, let the painting cure for 3 – 6 hours in between coats<. Most modern synthetic varnishes will be completely dry after only a few weeks. While it may feel dry to the touch within 24hrs or so, a several – week time frame allows all the layers a chance to adequately cure.

Tip: Speed up the varnishing process by planning to do a few pieces on the same day. This way they will all dry within a similar time period.

Traditional dammar varnish and synthetic varnish can 24-48 hrs depending on the thickness of the painting. Cold temperatures and high humidity can slow the drying time by several hours.

When varnished correctly and with care, artwork will have a removable protective layer, a unified sheen, and be ready to display and admired for many years to come!

Stay tuned in the following months for an Opus Video on varnishing and see this important process in action! Subscribe to the Opus YouTube Channel to be notified when its released! •