QUICK TIPS...
Varnish is more than simply a layer to protect your painting from pollution in the atmosphere and abrasion. It will also bring out the colours to the brilliance they had when you applied them.
1 - Ensure your painting is completely dry. To be safe, wait a couple of days.
2 - Check the paint is free from dust.
3 - Use a flat bristle brush to apply the varnish. If you don't want your painting to be too shiny, use a matt varnish rather than a gloss one.
4 - With the painting flat, work from the top to the bottom, applying the varnish in parallel strokes from one edge of the painting to the other. Always work in the same direction.
5 - When the first coat of varnish is dry, apply a second coat at right angles to the first. This will give you a good, even finish.
6 - Leave the painting flat for at least 10 minutes after you've finished varnishing to stop the varnish running down the painting. Then prop it up against a wall to dry, face inwards.
7 - To test whether the varnish is dry or not, touch the edge of the painting to see if it's still tacky. It should dry within a day or two, depending on the weather.
Tips:
• Always varnish the whole of the painting in one go. If you do only a part and this has started to dry before you do the rest, you'll end up with a line where the first bit ends.
• Try to have the same amount of varnish on the brush for each stroke so you put equal amounts of varnish on all parts of the painting.
• Work in a dust-free environment, otherwise dust particles will get stuck in the wet varnish.
DETAILED TIPS...
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Introduction
• Varnish is a clear coat applied over the top of an artwork. It has two main functions: to give an even sheen to the work, which will in turn help to bring out the full intensity and beauty of the pigments and to protect it from several different areas of attack, such as wear and tear and airborne grime and chemicals.
Sheen/Gloss Level
• When selecting a varnish one of the first questions that arises is that of the gloss level required. In general good quality acrylics will have a similar sheen level across their colour range. However the addition of water or many of the other mediums available to the artist may change the gloss levels dramatically. One must determine the level of gloss that is required. Most gloss and matt varnishes of the same type may be mixed to obtain the desired balance between the two. ie. satin or semi-gloss finish.
• All varnishes start out with a relatively high gloss level, some are not as glossy as others.
• Matt and satin varnishes have what are known as matting agents added to them to reduce their gloss levels.
• The matting agents are extremely fine particles suspended in the varnish or may be a wax which tends to sit mainly on the surface of the varnish. Both defract (scatter) the light passing through, which gives the matt appearance.
• The matting agents which are suspended in the varnish tend to have a longer life span and do not catch dust and dirt nearly as readily as the wax versions. The wax matting agents tend to mark very easily, however some artists prefer the soft and subtle reflection of light off this finish. (It is possible to use a very light coverage of wax applied over solvent based varnishes to achieve this same effect).
• If the artist wishes to apply many coats of a varnish (in excess of 5 coats) and requires a matt finish it would be advisable to use gloss for all but the last few coats. Too many coats of the matt varnish may give a cloudy appearance. This cloudy appearance is the concentration of the invisible matting agent starting to increase to the point of becoming visible.
• It is advisable to stir matt and satin varnishes before use to evenly distribute the matting agent so it does not form a concentrate in the bottom part of the container.
Water Resistance
• A varnish may help to make an otherwise water sensitive work waterproof. A professional grade artist acrylic should dry waterproof. However if copious amounts of water have been used to dilute the strength of colour by reducing the pigment concentration, so too the binder will have been reduced (as in watercolour techniques) sometimes rendering the acrylic water sensitive.
• The careful application of a varnish over the top will help to bind the work and improve the water resistance.(eg. Matisse Medium MM7 Polymer Gloss Varnish).
• The addition of Matisse Medium MM9 Acrylic Painting Medium to either the paint or the water used to dilute the paint at the point of application will also avoid water sensitivity.
Physical Protection
• A varnish may also be used to protect the work from physical abuse. Although not quite a shield of steel, some varnishes are extremely tough and heat resistant and will protect utility items very well.
Two-Varnish Finish System
• This approach to finishing off an acrylic work is universally recommended by conservators world over. More and more the larger galleries are requiring their artists to use it.
• Firstly one or two coats of waterbased acrylic varnish such as Matisse Medium MM 7 Polymer Gloss Varnish & Gloss Medium is applied to the work, then when thoroughly dry a coat of removable solvent based varnish such as Matisse Medium MM 14 Final Varnish & Gloss Finish is used to finish off the work.
• Using a removable varnish allows this varnish to be stripped off taking with it years of accumulated airbourne rubbish, then a fresh coat applied.
• Because both of these varnishes are acrylic they have the flexibility and elasticity to withstand the constant movement and expantion and contraction of most substrates. Therefore these varnishes will not crack or show signs of stress as they age. Neither will they yellow with age and they will help to protect the work from the destructive effects of ultraviolet light.
Step 1 Waterbased varnish
• A waterbased acrylic varnish affords the work it covers substantial resistance to physical and chemical attack. However this varnish is not completely impervious. Waterbased varnishes dry by evaporation thus the evaporating water can leave microscopic capillaries or holes through the varnish, which allows the paint to breath and cure.
• Allowing the paint to cure is of benefit however the small holes which are left behind have two potential drawbacks:
1 - The first is that of allowing water back under the surface of the varnish. This will not affect the paint or varnish chemically (as long as both the paint and varnish have cured) however, when the acrylic and water are combined their differences in refractive index mean they may look translucent or white.
This may, in turn produce cloudiness in the varnish over the work. This is only likely to occur when the work is literally soaking in water for a great length of time. Removing the water and applying an indirect warm dry heat can usually reverse this cloudiness (providing the varnish was cured prior to exposure to the water).
2 - The Second problem is that of dirt and grime catching in these holes, it is very easy for airborne rubbish to catch in the tiny holes which may in tropical climates, lead to the increased chance of bacteria and mould growing in these areas. However in the majority of cases the waterbased varnishes will be sufficient.
This varnish alone is most certainly better protection for the paint than nothing at all.
Leave at least 48hrs for the water-based varnish to dry before applying Step 2.
Step 2 Solvent-based Varnish
It has been found that by applying a removable final finish varnish such as Matisse Medium MM 14 Final Varnish:Gloss Finish after the waterbased varnish, conservators are able to easily clean and repair the works. When the work is to be cleaned the final varnish can be redissolved in Mineral Turpentine, the waterbased varnish helps to protect the paint during the removal of the original final varnish. Then a new coat of final varnish is applied over the clean original waterbased varnish.
This process is recommended for those artists seeking the best long term results from their materials and most certainly recommended for exterior mural work.
Water-Based Varnishes
• Put simply waterbased acrylic varnishes are made up of microscopic beads of acrylic dispersed in water. Acrylic is clear and water is clear however when the two are put together they appear milky. This is due to the difference in refractive index between water and acrylic.
• When light rays pass through this mixture they are defracted or bent to such an extent as to appear white. When the water evaporates away so too the "whiteness" goes with it. So it follows that if water is trapped in the varnish it will remain milky or cloudy.
• Water can be trapped in the film of varnish in a few ways:
1 - Recoating time. If a waterbased varnish is recoated before it has had time to dry it may go cloudy, even if it appeared to be touch dry and clear. The water from the second varnish coat will "rewet" the first coat and as described above will cause cloudiness. Drying times may vary from varnish to varnish and with the thickness of the coat and of course the climate. Follow directions on the label, if in doubt leave for 6 hours.
2 - Thin coats. If the varnish is applied too thickly it can start to cure on the top while water is still trapped on the bottom of the film layer, as described above this can lead to a cloudiness in the varnish film. To avoid this, apply the varnish on as thin as possible; do not flood the surface.
Varnish the work in a position closer to vertical than horizontal. This is most important when varnishing works with high relief or 3 dimensional surfaces, which can catch the varnish resulting in a milky pool. (Be careful to avoids runs in the varnish).
3 - Forced drying. Even if the varnish has been applied thinly but allowed to dry to quickly, water can be trapped in the varnish film. To avoid this DO NOT force dry the varnish. Hair dryers, heaters etc. can cause the varnish to dry and cure on the surface trapping water underneath. If heating is required use indirect heat not above 35 degrees C.
4 - Ambient temperature. Once upon a time in the days of the old masters varnishing was a very tricky business. The temperature and humidity had to be just right and had to remain that way while the work dried. Today's varnishes are much more forgiving however they too have certain limitations. As with artificial heating it is strongly advisable to varnish in a temperature range within 5 to 35 degrees C. with a medium to low level of humidity.
The minimum "film-forming" temperature is approx 5o c. Minimum film-forming temperature is the lowest temperature at which the varnish will bind together forming the tough interlocked coat that is desired. If the temperature climbs above approx 40 degrees C. the water may tend to flash off or evaporate far to quickly leaving the top of the film of varnish dry and cured, trapping the water underneath leading to the cloudiness described above.
Extremes of humidity should also be avoided. In ultra dry climates the water may tend to flash off quickly as described above. Whilst in extremely humid conditions the water may not evaporate out fast enough and be trapped inside the varnish. However humidity is not as much of a concern as the temperature and will only present a problem in extreme climates.
• For the most part, these problems should never arise however it has been discussed more out of interest for those artists in quite abnormal conditions.
Water-Based Acrylic Varnishes
• Dilute with water. Most waterbased varnishes can be diluted with water. (Some should not; check the label). Diluting with water will make it easier to brush the varnish out and also allow a thinner coat. If diluting equal parts with water so as to thin the varnish, then 2 coats should be applied.
• Spray. It is possible to use an airbrush or spray gun for larger areas with Matisse Medium MM 7 Polymer Gloss Varnish & Gloss Medium & Matisse Medium MM 6 Polymer Matt Varnish water based. Dilute either of these varnishes with water up to equal parts and spray apply. An approved mask should be worn when spraying with acrylic varnishes (as with the paints) as even though the varnishes are non-toxic, INHALATION SHOULD BE AVOIDED. (courtesy of Matisse Derivan)
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