How to varnish an oil painting

How to Varnish an Oil Painting

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Varnishing an oil painting: it’s the final step before finishing your masterpiece. So it’s not something you want to rush. 

A layer of varnish can dramatically enhance your painting, making the colours look brighter and shadows deeper.

By applying a layer of varnish, you can unify the surface appearance of a painting and protect it for years to come. 

Top product pick: Gamvar

Buy Gamvar here.

Gamvar is incredibly easy to apply. As soon as your painting is dry to the touch, you can varnish. There are three different types of Gamvar finishes available. Gamvar Gloss will intensify the colours of your painting.

It’s the most convenient type of oil painting varnish to use and is beginner friendly. Read on to find out more about the different types of varnishes available, what other supplies you need, and how to apply the varnish. 

Why should you varnish an oil painting?

 
  • You can change the surface finish to either gloss or matte.
  • It will increase the intensity and depth of the colours (though this is mainly applicable to using a gloss finish).
  • Varnish will protect colours from UV light. UV can cause some pigments to fade over time. It’s not advised to leave paintings in direct sunlight anyway, but with a layer of varnish, you can be sure that the colours will be more resistant to fading.
  • It provides a protective layer for the painting from general wear and tear. Plus, a varnished painting is easier to clean.
  • If you varnish a painting, it gives you the option to restore it at a later date. When applied correctly, the layer of varnish sits separately from the paint below. This means you can remove it, along with any dust, dirt or wear and tear it has accumulated over the years with solvent. Applying a new layer restores it so it’ll look like it did the day it had its first coat of varnish. It’s just like replacing the glass on a framed picture, the glass absorbs all kinds of impact; it becomes scratched, smudged and dirty—if you replace the glass for a shiny new piece, the picture below suddenly looks new again. 

When do you varnish?

Oil paintings take a long time to feel dry to touch. If you’ve painted with fairly thin layers of paint, it should take a few days to be dry enough to handle. But oil paintings don’t just dry, they cure.

‘Curing’ is simply the oxidisation process that both oil and pigment undergo to dry and set completely.

If you have thinned any layers of paint with solvent such as turpentine, layers will dry by evaporation, leaving the oil and pigment behind to react with oxygen and harden on the canvas.

An oil painting with thin layers should only take a few months to cure. However, in the case of paintings with thicker layers, it can take anywhere between six months and a year to cure fully. If you have painted with thick impasto layers, it could take longer.

Traditional varnishes like damar resin should only be applied after the curing process is complete.

The reason you should wait instead of varnishing straight away with damar resin, is that whilst the paint is curing, it is ever so slightly contracting, meaning that any layer painted on top that has been thinned with turpentine (the ingredients of picture varnish is most often damar resin and turpentine) could crack. 

Another important reason to wait until the painting has properly cured to varnish with damar resin is that if varnished too soon, the varnish doesn’t become a separate removable layer and instead melds to the artwork. Restorers clean oil paintings by removing the layer of varnish to reveal artwork that nothing has touched since the day it was varnished. All the dust and grime that accumulated on the surface of the varnish can be removed with the layer of varnish, and a new layer can be painted on the surface.

There are ways around having to wait this long for a painting to set though, using a synthetic formulation such as Gamvar which allows the oil to oxidise underneath, or by applying a very thin layer of varnish to restore colours and unify the painting’s surface which allows the painting to continue curing below.

What to use as a varnish?

I’ve outlined three different types of varnish below, there are other types of varnish that have been used to protect artwork in the past, but these are most commonly used today.  

Here’s a rundown, with product recommendations:

Traditional varnish

Winsor and Newton Damar Varnish Spray: Buy it here.

Chelsea Classical Studio Lavender Varnish (liquid form): Buy it here.

Traditional varnishes include Damar, Copal and Amber. 

Copal and Amber have a golden appearance but crack and yellow over time. They have a very hard coating, but are not ideal to use due to how the surface can change over the years.

Damar varnish is more widely used, and is considered a ‘soft varnish’. It is similar in appearance to the more historical varnishes Copal and Amber.

This is a mixture of damar resin that has been thinned with turpentine. You can buy pre-made damar varnish that you can apply straight to your painting, or damar resin that you have to dilute yourself. It will become very tacky when it dries so you’ll need to prop it upright with a cover to avoid dust settling on the surface. Always work in a well ventilated space too. 

Because it’s a natural varnish, it will yellow over time and it becomes brittle when it dries. With changes in temperature and humidity, canvas can expand and contract, leaving the layer of damar to crack.

You can use damar as a glazing medium, by mixing it with linseed oil and pigment and applying it to the final layers of your painting. This will give your painting a sheen and the linseed oil will provide flexibility in balance to the brittleness of the damar resin, preventing cracking. 

Retouch varnish

Retouching Varnish Spray: Buy it here.

This is more of a temporary solution. It can be applied to the painting when touch dry, to temporarily restore the surface. This comes in a spray form. If you are delivering a painting to a collector and the painting hasn’t fully cured (but is dry and stiff) you can apply retouch varnish, then around a year later apply the final layer of varnish.

Gamvar

Gamvar Picture Varnish: Buy it here.

This is a synthetic varnish that goes on like water, and saturates your painting giving it a unified appearance. The coat is completely clear and won’t yellow over time.

The great thing about Gamvar is that you don’t have to wait until your painting has oxidised to apply it. You can apply when the paint is touch dry and firm. This is because the varnish allows oxygen to seep through the film after it has dried, leaving the lower layers of the painting to cure. This is the varnish I use, and many other artists do too, just because of its ease of use. It means that if you have commissions, or need to submit your work to a gallery for a show, then you don’t have to wait a whole year for the painting to cure. 

Different finishes of Gamvar

You can buy Gloss, Satin or Matte. Realist painters usually opt for gloss, as it brings out colour values and deepens the appearance of your work. Matte varnish can make the painting appear dull.

Now you know your options—what you can use to varnish an oil painting and when best to use them in relation to the drying process of your painting.

So now I’ll walk you through HOW you go about varnishing, step-by-step.

What tools do you need to varnish a painting?

  • A brush for varnishing: here’s our pick.
  • Your varnish of choice.
  • Something to prop the painting against (i.e. an easel).
  • Something to cover your painting with to avoid dust sticking to it.
  • A board to lay your painting on, or something to stop any varnish dripping onto your table. 

Is your painting ready for varnish?

Oiling out

If you notice dull spots on your painting, it means that parts of the binder have been absorbed by previous layers of the painting. This can occur if you were painting on an absorbent ground, or if you thinned your first layers with turpentine (this can sometimes soak up the oil from the top layers).

If you go ahead and varnish at this point, the varnish can just accentuate the dull spots leaving an uneven appearance. 

To even out the surface, paint on a very thin layer or linseed oil with a soft brush. Then wipe over with a lint-free cloth to remove most of the oil on the surface. This process is called oiling out. It will remove those ‘sunken in’ areas, where only the pigment has been left dry on the surface. Wait for this to dry or cure completely, depending on which varnish you choose before applying.

This a fairly simple step, but if you want to learn more read about oiling out here.

Further preparation

Wipe your painting over with a lint-free cloth to remove any dust from the surface.

Your painting should be completely dry. The paint itself and the humidity of the environment. There shouldn’t be any moisture on the surface of the painting, try to work in an environment which has a medium temperature and low humidity.

How to varnish your painting 

  1. Lay your painting flat on a board. If you’re laying it on a table, you could use a tablecloth to cover beneath your painting, as you’re likely to get some varnish run-off.
  2. Pour your varnish into a clean dish (make sure it’s free of dust). This way you can measure carefully how much you need for the painting. Careful not to pour out too much, you’ll only want to spread a thin layer over the painting. It’s easier to add more varnish to the painting that to have to remove parts you’ve already poured on.
  3. Make sure your brush is totally clean.
  4. Apply the varnish in long strokes. You’ll need to apply it as evenly as possible. This requires a minimal pressure, painting in the same direction with the strokes slightly overlapping. 
  5. Make sure to varnish the entire painting in one sitting. You don’t want there to be visible lines where one layer has dried before another.
  6. You only need one layer.
  7. Assemble the cover. You can get creative with this and use whatever you have around the house. I usually prop my canvas up at a 90 degree angle with my easel. I then put a clean plastic cover over the top (making sure it’s not touching the painting).
  8. Gamvar takes 18-24 hours to dry. Damar varnish will take several days.

How to varnish your painting using spray

  1. Prop your painting up vertically in a dust-free room. It’s ideal for both the room and the spray to be at room temperature.
  2. Check the nozzle for build up of varnish residue and clean it if there’s any stuck in there.
  3. Make sure there’s nothing directly behind the painting—you don’t want to varnish your wall by accident!
  4. Shake the can—read the back of the can, but shake it for between one and two minutes; this way you can ensure you get an even finish.
  5. Hold the can away from the painting—40cm is a good distance.
  6. Work in a fairly quick motion to get an even and thin coat.
  7. You can apply multiple layers. Each layer will take around 20 minutes to dry fully, but check the can of your varnish to make sure.

Problems that can arise when varnishing

Whether you’re varnishing with Damar Resin or Gamvar, there are two potential problems that can arise and they are pretty common.

Beading

This is where the varnish doesn’t stick to certain areas of the painting and collects in patches, giving an uneven surface finish. The worst case is when you don’t pay attention to it as it dries and you return to the painting the next day to find that some areas of the painting are still exposed and the varnish has dried.

Beading is caused by a slick surface. If you’ve painted in layers that are very oil rich then this will be the cause. Before varnishing, the paint needs to be ever so slightly abrasive. You can rub a nylon brush over the surface first and apply a tiny amount of rubbing alcohol with a soft cloth. This will make the varnish stick better. 

I’ve experienced beading a few times and what helped me was scrubbing the varnish with a bristle brush and as it was drying continuing to scrub the surface every now and again to ensure even coverage.

If your varnish has dried beaded up, then can remove it with odourless mineral spirit and apply again.

Bubbles

Bubbles in the varnish occur when you’ve applied too much. With Gamvar especially it’s better to apply in small amounts and layer if you need to. If you’ve applied too much and there are bubbles, soak up the excess varnish with a cloth.

Finally

If you’re just beginning on your oil painting journey and you’re not quite sure what supplies to get, start with this beginner’s guide. It’ll teach you about all the tools and materials you need to start oil painting and give you valuable advice on how to use the materials to get the best results.

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