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Varnishing

Date: 02-07-2023
News, Tips & Info

 

 

Varnishing


Varnish is a resin that’s dissolved in fluid so that it can spread across a painting. When the carrier fluid evaporates, it leaves the resin behind to harden into a protective, even-sheen film. We have a wide range of varnishes to choose from, offering specific properties to suit all painting styles. Selection is easy by asking yourself these questions:

 

Why Varnish?

 

Varnish protects your paintings. After years of gathering dirt, varnish is removed revealing the original colours underneath.

Varnishing is done to protect your painting from atmospheric pollutants. After building up a patina from many years on display, a varnished painting can be simply restored to its original brightness by removing the varnish along with all the dirt stuck to it. Cleaning an unvarnished painting is much more difficult, as the grime must be carefully removed directly from the paint layer.


Varnishing is also used to adjust the painting’s surface sheen. Some artists wish to even the surface sheen of their painting, to increase depth or reduce glare, or to homogenise the differing degrees of gloss and matte in the colours and mediums they’ve used. Most varnishing will bring a universal surface sheen to your work.


While some varnishes have UV filters, these are mainly to prevent the varnish from discolouring rather than protecting the artwork from fading. For UV protection of low-lightfast materials (e.g. collage), you can apply Golden UV Topcoat, a gel with strong UV filters, or frame behind UV glass.

 

What type of artwork do you want to protect or adjust?

Varnishes are available for the main types of paint: acrylic, oilcolour, watercolour and gouache. There are also varnishes that work best for mixed media work, as they can be used across all media.

 

There are different varnishes for different painting media, and usually available both as liquid for brushing on and aerosol for spray on. If using in an enclosed space, best invest in a proper respirator.

 

Varnishes for Acrylic Paintings

Acrylics remain porous when dried, so airborne dirt can be easily drawn into the surface through changes in humidity. They can be protected by using either water-based or spirit-based varnishes. Water-based varnishes are easier to clean up from, while spirit-based varnishes give superior clarity and protection.


The best water-based varnish is the brush-on Golden Waterborne Varnish with UVLS (Ultraviolet Light Stabilizers). Golden Waterborne Varnish is made with pure acrylic resins and dries to a protective, flexible, dust-resistant surface over acrylic paint. It is available in Gloss sheen. Due to the removal method using ammonia, it is highly recommended that you paint an initial Isolation Coat to provide a barrier between your work and the varnish, so future removal of the varnish is easier. You can buy Golden Isolation Coat or thin Golden Soft Gel Gloss 1:1 with water, apply and allow to dry for 1 day before varnishing.

 


Golden MSA Varnish is spirit-based and provides a harder, lower tack surface that is much less susceptible to dirt and is more mar resistant than Golden Polymer Varnish. It also suffers significantly less from foam generation and pinholes that can affect the clarity and appearance of the finish. MSA Varnish produces an extremely level finish and can coat slick supports including glass, most plastics and metals. It is available in aerosol and liquid options, and the liquid must be thinned with white spirits before use.

 

Varnishing is useful to homogenise the various matte and gloss areas that often results from oilpainting.

 

Varnishes for Oil Paintings

Oil paintings are ready for varnishing 6-12 months after finishing, a wait that annoys some painters, but there’s a very good reason to practice patience. Oilcolour dries by absorbing oxygen into the unsaturated acids of the oil binder, changing the molecular structure of the oil into a new compound. This new, fully dried paint film is impervious to solvents such as turpentine, so is unaffected by the spirit-based varnishes used on oil paintings. Until this oxidation has taken place, the oilpaint is susceptible to solvent in the varnish, which can re-wet or soften the paint layers causing immediate and potentially irreversible problems!


Fortunately, if you need to even the surface sheen of your recently completed oil painting sooner than expected, you can use a Retouch Varnish. Though also available as a brush-on, Schmincke offer an aerosol Retouch Varnish that is safer to use after just 30 days. Retouch varnishes are used to prepare old oil paintings (older than 6-12 months) for reworking.


Schmincke produce a wide range of liquid and aerosol varnishes for oilcolour. Their pure Dammar resin varnishes offer exceptional refractive qualities to enhance the look of your oilcolour, while their Wax Varnish can be buffed onto the painting to achieve a soft, natural glow. Unique synthetic resin formulations provide elastic, age-resistant protection for both brush-on and spray applications.

 

Varnishes for Watercolour and Gouache

From the accidental drop of water to unwanted attention from insects, watercolour and gouache paintings remain vulnerable. There are a range of aerosol varnishes from Schmincke and Pebeo that offer protection without altering the delicate look of your painting, and spirit-based varnishes can also be used, though their look will be evident.

 

One varnish for almost everything

Especially developed for mixed use, Schmincke B72 is an aerosol varnish that gives protection to pencil, charcoal, pastel, watercolour, gouache, acrylic, oilcolour, ink, tempera, prints, photographs, and gold leaf. The only thing it won’t do is even out the sheen, which is what makes it unique.


What sheen do you want?


You can alter the final look of your painting by adjusting the surface sheen. Most varnishes will deliver a homogenous sheen, when evenly applied, and you can choose how glossy or matte to make it. Changing the optics of your painting will change the appearance of some colours, so let’s look at the options.

 

The sheen of each varnish affects the tone of the colours underneath. You can see the effects from Gloss, Satin, and Matte (left to right), with the unvarnished in the left of each image, and the varnished on the right.

 

Light passes easily through a gloss surface, so Gloss varnish adds depth to colours, deepening especially the dark tones of you painting, bringing back a “wet” look.


When light hits a matte surface, it scatters, so Matte varnish imparts a velvet sheen that flattens colours. Dark colours in your painting will lighten due to the reduction in refraction. It is recommended that no more than two coats of matter varnish be applied.


Satin varnishes are an excellent choice when you don’t want too much glare from a gloss surface, yet you want more depth than the matte offers. You can also layer up gloss and matte varnishes, if aerosol, using the Gloss first and finishing with Matte, to create your own Satin surface, or by mixing them if using liquid varnishes.


If you love the way your painting looks and don’t want to mess with it, yet still want protection, Schmincke B72 is a great choice. This varnish will retain the original variation of surface sheen while providing a protective layer.

 

How do you want to apply the varnish?


While water-based varnishes are only available as a liquid, you can choose spirit-based varnishes in both liquid and aerosol forms.

 

A good varnish brush will hold plenty of fluid and spread it thinly and evenly across your painting.

 

Liquid varnish is painted on using a soft but strong brush. This application immediately provides an even and significant layer of varnish, with sufficient protection in just 1 or 2 coats. You will need a good varnishing brush, one that has a sharp edge (a “toothy” edge will result in brush lines), and this requires a bit of cleaning, especially with spirit-based varnishes. The da Vinci 5040 Mottler will put varnish down smooth as glass, while their 2429 Synthetic Bristle is a good, inexpensive alternative.

 

Spirit-based varnishes are available as aerosols, making varnishing exceptionally easy for everyone.

Aerosol varnish is very convenient: there is little preparation or clean-up, and you don’t need a decent dedicated brush. However, spray-on varnish requires more applications to reach a good protective layer, and care must be taken to achieve an even surface.

 

The Tricky Bit: Varnishing!


So now you’ve decided why you’re varnishing and what, you’ve picked out the sheen you want and how you’re going to apply it. All that’s left is to varnish… and even for seasoned painters, this is a process that can be fraught. Fortunately, there is more stress in the thought of ruining an artwork you’ve invested so much time and energy into, than there is risk of actually doing so. If you follow some basic procedures, there will be no irreversible disasters.

When is the best time to varnish paintings in NZ?

Firstly, always varnish on a fine, mild day. High humidity, and especially rain, can cause “blooming”, where moisture is caught in the varnish layer; and the temperature needs to be between 15⁰C and 25⁰C for the resin to cure properly. In some parts of the country, this might mean several months’ worth of paintings get done during a brief window in the weather.


Of course, you can control the elements if you’re able to varnish indoors, but it’s often best to varnish outdoors where there is plenty of airflow. Due to the toxic nature of spirit-based and aerosol varnishes, they’re not suitable for use inside a home, and in the studio, I highly recommend a respirator and googles.


Before varnishing, give your painting a good dusting. If you haven’t varnished before, please test first on a discarded work, not on your masterpiece! And ALWAYS read the instructions on the container.


Varnishing with an aerosol

Using a good quality aerosol is the simplest way to varnish your painting. Set up your painting in a vertical position. Shake the spray can well – Golden Paints recommend 2 minutes and have made a funny video to help pass the time

 

  

 

Test that the varnish is properly dispersed by spraying to one side – if it comes out in a jet, something’s not right, and best it happens away from your work! Now spray from a distance of 30cm to 40cm across and down the painting using a circular motion. To prevent droplets forming, 1 or 2 passes are sufficient, then lay your painting down to dry. To prevent the spray nozzle becoming blocked, up-end your can and spray out the excess – it will blow clear in a second or two. After an hour, apply a second coat. While the varnish is touch dry in an hour or so, the resin will continue to harden and increase in clarity for several days, so avoid stacking or shipping until then.


Varnishing with a liquid

Set up your painting lying flat on a level surface. If you have to varnish vertically due to extra large size, mural, etc, be sure to apply the varnish very thinly to avoid runs. If using a Satin or Matte varnish, shake gently to mix. Pour a small amount into a saucer (you’ll be amazed how far good quality varnish goes) and load your brush. The size of your painting will determine the size of the brush. Start at the top and work your way down, brushing out the varnish into the thinnest film possible and dividing the work into areas covered by each loading of the brush. These may be based on a systematic grid-like sequence or may follow natural boundaries of the piece. Do not go back into an area once you’ve left it: spirit-based varnish becomes tacky very quickly and if you go back you risk pulling the sticky resin. If you’ve missed a spot, you can retouch or get it on the second coat once it’s dry. Likewise, if a bug flies into the wet surface – leave it until the varnish is dry and the insect can be brushed easily from the film.

 

Some artists apply varnish by following the existing brush marks, so that any visible varnishing strokes are indistinguishable from the painting.

Two thin coats, with half a day between, are better than one thick coat of varnish, which will take longer to harden and could result in a cloudy film. When applying a satin or matte varnish, never apply more than two coats, as it can result in loss of clarity. The varnish will continue to harden and increase in clarity for several days, so avoid stacking or shipping until then.


Wash your brush as soon as possible. If using spirit-based varnish, rinse with turpentine or turpentine substitute. Use da Vinci Brush-cleaning Soap to lather the bristles, making sure to push the soap deep into the brush head; rinse and repeat until clean. It may require you to leave the brush lathered up overnight and giving it another session the next day. Make sure your brush is thoroughly dry before using it with spirit-based varnish again.


Of course, not everyone varnishes their work. It’s up to you to decide whether the work warrants it, for protection, or for aesthetic reasons towards the surface. Varnishing will enhance your painting, and knowing how to do so is an important skill for every painter.


Further reading: https://www.goldenpaints.com/technicalinfo/technicalinfo_msavar


© Evan Woodruffe for Gordon Harris Ltd 2023.

 

Golden Varnishing