A Guide to Varnishes
In order to protect your oil, acrylic or watercolour painting from dust, dirt, UV and moisture, we strongly recommend varnishing finished work. Many artists see varnishing as an essential part of the painting process, but it's worth considering that it will inevitably alter the appearance on your work, making it either shinier or more matte, so all painters must ask themselves whether the protection of their work is worth the slight alteration of the appearance. If the answer is yes, then varnish!
What is Varnish?
Varnish is a clear layer applied to fully dried ('cured') work. Varnishes for oil painting are made from a resin (alkyd or dammar) suspended in a solvent, usually turpentine. Acrylic varnishes are made from acrylic polymer emulsions. Varnishes are hard and less flexible than dried paint. Dust and dirt is easily removed from a layer of dried varnish. Moisture will not penetrate varnish, and in most cases, varnish will add another layer of UV resistance to your work.
Which Varnish Should I Use for My Painting?
All paintings should be varnished with removable varnish. This is a precaution in case the varnish is marked or stained. Removable varnish is not necessarily that easy to remove! But it can be done, even if you need to acquire the assistance of a picture restorer. More on this later.
For Temporary Protection of Oil Paintings:
Retouching Varnish can be applied to touch-dry layers of paint; you will not need to wait until the oil paint has fully cured, which can actually take months or years depending on the thickness of the paint and the humidity of your environment. Retouching varnish will offer a UV resistant temporary protection of work prior to the final layer of varnish. However, it's structure is insufficient to act as an alternative to a final picture varnish, so you will need to use a proper picture varnish over the top when your painting is completely dry.
For Permanent Protection of Oil Paintings:
Do you need to Oil Out your work before varnishing?
If some areas appear duller than others on the surface of your painting, it may be because some oil colour has sunk into the surface, which is normal. You may wish to unify the sheen prior to varnishing, and this can be done by 'oiling out'. Oiling out can be done when the painting is touch dry. To oil out, simply take a lint free cloth and dip it in painting medium. Then go over the whole painting gently rubbing the painting medium on with the lint free rag in circular motions. This will unify the sheen on your painting. You will then need to wait until the painting is fully dried before you can varnish it.
This video by Winsor and Newton shows you how to oil out your painting.
Once your work is ready for varnishing, you have the option to use either a resin based picture varnish, a mineral spirit varnish, or dammar varnish.
Dammar Varnish (Removable)
Dammar varnish is the traditional varnish recipe that has been used by artists for hundred of years, however it is sometimes known to yellow over time, and generally the modern recipes are thought to possess greater longevity.
Picture Varnish (Removable)
Picture Varnishes are available in a bottle ready to be applied with a brush, or in aerosol cans. Please note that aerosols cannot be shipped by regular post and may not be available to certain destinations without incurring additional shipping charges . Some people prefer to use an aerosol because they find it easier to apply a thinner, more even layer to their work than with a brush, but it is a case of personal preference. We think it's best to try both and see. Picture varnish tends to be available in matte and gloss.
MSA Varnish (Removable-ish!)
MSA Varnish is an extra tough recipe that is particularly good for work that may be exhibited out of doors. It can also be used on acrylic paintings, and is available in bottle or aerosol can. It's also pretty difficult to remove so we would not recommend it for paintings that are hung indoors.
For Acrylic Paintings:
Remember to apply an Isolation Coat
Prior to applying a final layer of varnish to your acrylic painting, we suggest you put on an isolation layer, so that if you ever need to remove the varnish it will be harder to inadvertently remove the painting underneath it too. A good isolation coat is to mix a 2 parts Soft Gel to 1 part distilled water. Mix the amount required with a palette knife and leave for 24 hours to settle prior to applying with a brush. Golden Paints have a good video on how to make a good isolation coat. Click here to view.
Polymer and Acrylic varnishes are recommended for finished acrylic paintings that will be hung indoors. For work that is likely to be kept outside MSA varnish can be used.
For Watercolour Paintings (non-removable):
There is even a varnish by Daler Rowney for watercolours and posters, to protect delicate work on paper or card.
Craft Varnishes (non-removable)
General purpose craft varnishes are for surfaces such as wood paper and metal. They are non removable and not for use on fine art paintings.
How to Apply Varnish
There's a great in-depth article on how to apply varnish by Julie Caves on the blog. Click here to view.
But here is a brief summary of the main things to remember when varnishing.
- Use a lint free cloth to try and remove any dust or dirt on the surface of your painting. You may wish to dab the cloth in a little solvent, but not too much if you are varnishing an oil painting.
- Varnish in a well ventilated, dust free environment.
- Ensure your painting is fully dry. Remember this can be a case of up to a month for acrylic paintings, and even years for oil paintings. The paint layer must be dry throughout, it can't just be touch dry as varnish is likely to crack. Drying times are dependent on thickness of paint and humidity of the environment.
- Decide how much sheen you want on your painting. Gloss makes colours lustrous and brilliant, however it can be highly reflective and also show lumps and bumps. The matting agent in Matte varnish has a white tint to it, so although matte varnishes will help to conceal the uneveness of a paint surface, colours may appear a little paler after application. Remember to shake your matte varnish prior to application as the matting agent can sink to the bottom of the bottle, but ensure that the varnish does not have any foam or bubbles in it when it is applied. You can mix both matte and gloss varnishes to get a satin finish, which is a popular compromise.
- Use a soft brush that will not leave brush marks. The Jackson's synthetic mottler is a popular choice for this.
- It's good to varnish near a window in daylight - raking light across your canvas will help you see where you have already applied varnish during the process.
- 2-3 thin coats that have been allowed to fully dry between layers is always better than one thick layer.
- Leave the picture flat until the varnish is touch dry. Once it is touch dry, you can lean it against a wall with the front of the painting facing downwards and towards the wall. This will protect it from dust settling on it while it proceeds to fully dry.
How to Remove Varnish
Varnishes for oil paintings are removed with the same solvent that will remove the paint i.e. turpentine or Zest-It. All varnishes should be removed with utmost care and incredibly slowly, preferably by a restorer, who would use a cotton bud dipped in a little of the solvent. The varnish has been removed when colour starts to come off on to the cotton bud, and that's when a new area needs to be worked on.
White Spirit (there are special Artist's white spirits available) can take a thin layer of dirty or discoloured varnish off without having to remove the whole layer, but again this needs to be done very slowly and carefully so it is done in a uniform manner.
Polymer varnish can be removed with household ammonia. This will not remove the paint from your work but it may alter it slightly (there is a possibility of dulling the paint surface). Again, remove with the utmost care.
Varnishing your painting requires care but when done correctly will help to protect your painting, and keep it looking as fresh as the day you finished the work for hundreds of years to come. The public galleries of the future will thank you for your efforts!