Varnish is a transparent, hard, protective film that provides a protective layer over artwork. Varnishes are traditionally a combination of drying oil, resin, and solvent. Varnish finishes are usually glossy but may be made to produce a satin or matte surface by the addition of "flatting" agents. Varnish has little, or no color, is transparent, and has no added pigment, as opposed to paint or stain, which contains pigments or dyes and generally range from opaque to translucent. Varnishes are also applied between layers of paint to isolate them or over substrates, such as wood, to seal the surface and reduce absorbency.
Varnishes are applied to artwork for different purposes. Varnishes can change the surface appearance, making the surface more matte or glossy or unifying areas of a painting with a more unified surface appearance. Varnishes applied over paint with high pigment concentration, such as tempera, increase color saturation. Varnishes protect the underlying surface and allow the painting or object to be cleaned. They also can similarly consolidate artwork to a fixative for charcoal or pastel. Some varnishes provide additional protection in the form of Ultraviolet Light Stabilizers (UVLS), which dissipate UV radiation before it can penetrate the paint layer where damage may occur. These varnishes are especially useful for fugitive materials, such as dyes, but will not render them completely lightfast. The thicker the varnish film with UVLS, the greater the protection.
Varnish Properties
Varnishes should be removable to allow for cleaning without damaging the underlying surface. Using a removable varnish provides a valuable tool to anyone trying to restore or clean the painting by allowing it to be solubilized and removed, taking with it any surface contamination. The varnish must be flexible enough to move with the painting surface and hard enough to resist the retention of grime and dust by providing a non-tacky surface. Depending on the substrate and environmental conditions, it must be formulated with the correct porosity to allow moisture to pass through or provide a barrier. It should have good chemical and water resistance. Over time it should resist discoloration caused by factors like humidity, heat, and visible and ultraviolet (UV) light sources. Finally, the varnish must possess excellent clarity without discoloration or fogging.
Resin Content
We've made selecting varnishes and mediums easy by noting the resin content as a percentage. For example, 31% resin w/v means 31% resin weight of the total volume. In this example, 100 ml of varnish contains 31 grams of total resin. With this, you can easily calculate the resin content of your paint as you use it in your work.
Varnish Appearance
Due to differences in the refractive index of the varnish and the surface underneath it, varnishes alter artwork's appearance and serve a vital aesthetic function. A varnish that does not alter the appearance of the painting cannot be wholly achieved. Varnishes are most successfully employed that compliment the painting. Varnishes are offered in a range of finishes, from gloss to matte, to allow the artist to control the final appearance of the work of art. Different finishes of the same varnish type can usually be combined or used sequentially to achieve the desired level of surface sheen.
Varnish Types
Besides traditional varnishes based on natural resins, such as dammar, copal, and mastic, newer varnishes based on synthetic resins, such as ketone, aldehyde, polyvinyl acetate, polybutylacrylate and sold under such names as Laropal A81, PVAA/AYAB, PVA/AWAB, Mowilith 20PVA, Ketone N, Arkon P90, Regalrez, and polybutylmethacrylate, are available to artists. Conservators use the raw materials for their suitability as a varnish for modern and earlier works of art.
The most important traditional varnish is dammar. It is the only traditional coating system still widely used and recommended as suitable for artwork. Other resins, such as copal or mastic, although still in use, suffer from cracking and extensive yellowing and become increasingly difficult to remove from a painting over time. Although dammar does turn yellow to brown within about fifty years of normal exposure conditions, it is still removable from an oil painting surface without significantly affecting the paint layers below.
Spirit Varnishes
A spirit varnish consists of a resin and a solvent. After the varnish is applied, the solvent evaporates, leaving a continuous film of hard resin. In traditional varnishes, resins are derived from plant or insect excretions, are dissolved in a suitable solvent, and are called a spirit varnish or solvent varnish. Traditional resins include amber, dammar, copal, rosin, sandarac, elemi, benzoin, mastic, balsam, and shellac. The solvent may be alcohol, turpentine, or petroleum-based. Some resins are soluble in both alcohol and turpentine. With certain resins, petroleum solvents, such as aliphatic solvents (i.e., mineral spirits, kerosene) or aromatic solvents (i.e., xylene, toluene, V&PM naphtha), can substitute for turpentine.
Over the centuries, many recipes were developed that involved a combination of resins, drying oils, and other ingredients, such as wax. These impart unique qualities to the final varnish film, such as increasing the matte or gloss of the varnish.
Synthetic resins, such as phenolic, rosin ester, aldehyde, ketone, etc., gradually replaced natural resins in commercial varnishes because they resist yellowing and can be more easily removed from the picture.
Neil's Best Dammar Varnish
Neil's Best Dammar Varnish
Neil's Best Dammar Varnish is a traditional varnish of dammar resin dissolved without heat in pure spirits of gum turpentine and aged one year. Use Neil's Best Dammar Varnish as a final glossy picture varnish over well-dried oil paintings after 6-12 months, or add Wax Paste for a satin finish. Add to oil colors for luminosity; use to make egg-oil emulsions or as a quick-drying paint medium.
Resin Content: 31% resin weight/volume
Available in 8 fluid-ounce (236 ml) cone-top cans.
Dammar Picture Varnish
Dammar Picture Varnish
Dammar Picture Varnish is a varnish of dammar resin dissolved without heat in a blend of aliphatic and aromatic solvents to minimize yellowing. Add UV Stabilizer to inhibit yellowing caused by ultraviolet (UV) light. Use Dammar Picture Varnish as a final glossy picture varnish over well-dried oil paintings after 6–12 months, or add Wax Paste for a satin finish. Add to oil colors for luminosity or as a quick-drying paint medium.
Resin Content: 31% resin weight/volume
Available in 8 fluid-ounce (236 ml) cone-top cans.
Isolating Varnish
Isolating Varnish
Isolating Varnish is a mixture of sandarac and mastic resins. Isolating Varnish dries fast to a clear finish—ideal for isolating paint layers as a fixative and reducing the absorbency of grounds. If necessary, it can be thinned with denatured alcohol.
Resin Content: 10% resin weight/volume
Available in 8 fluid-ounce (236 ml) cone-top cans.
Sealing Varnish
Sealing Varnish
Sealing Varnish is a varnish of Manila copal and elemi gum (a plasticizer) resins in ethyl alcohol. It dries fast to a hard finish that resists turpentine and mineral spirits and sands easily, making it ideal for sealing wood panels and absorbent grounds. The properties of this varnish are 1) relatively hard resin (copal) used in the formulation; 2) rapidly penetrates the pores of the wood and other porous materials; 3) easy to apply whether by brushing or spraying; 4) complete and rapid drying (due to the low solvent retention), and 5) easy to sand. If necessary, it can be thinned with denatured alcohol.
Resin Content: 26% resin weight/volume
Available in 8 fluid-ounce (236 ml) cone-top cans.
Oil Varnishes
Oil varnishes typically consist of drying oil, resin, and solvent. There are many different types of drying oils, including linseed oil, tung oil, and walnut oil. These contain high levels of polyunsaturated fatty acids that harden through oxidation. Resins typically used in oil varnishes are either derived from natural sources, such as amber, copal, mastic, dammar, and sandarac, or synthetic substances, such as alkyd, polyurethane, ketone, and aldehyde.
Oil varnishes do not harden in the same manner as do spirit varnishes through evaporation. Drying oils cure through an exothermic reaction between the polyunsaturated portion of the oil and oxygen from the air (called autoxidation). Initially, "varnish" referred to finishes made entirely of resin dissolved in quickly-evaporating solvents, either ethyl alcohol or turpentine. The advantage was that spirit resin varnishes dried rapidly compared to oils; in most cases, they cure practically as soon as the solvent has fully evaporated. Contrastingly, untreated or raw drying oils may take weeks to cure, depending on environmental factors. In modern oil varnishes, partially polymerized drying oils with added siccatives or dryers have to cure times of less than 24 hours. It has long been a practice to combine drying oils with resins to obtain favorable features of both substances in a varnish.
After being applied, oil varnishes harden after evaporation of the solvent and by chemical reactions between the drying oils and oxygen from the air. Oil varnishes remain liquid even after evaporation of the solvent but quickly begin to cure, undergoing successive stages from liquid or syrupy, to tacky or sticky, and to "dry to the touch" and "dry hard." Environmental factors, such as heat and humidity, play a huge role in the drying and curing times of varnishes. In traditional oil varnishes, the cure rate depends on the type of oil used and, to some extent, on the ratio of oil to resin. The drying time of oil varnishes may be hastened by exposure to light or heat. Many varnishes require organic solvents, such as turpentine or mineral spirits, to hasten drying, as well as the use of metallic driers. All drying oils and certain alkyds produce heat during the curing process. Therefore, oil-soaked rags and paper can spontaneously ignite if piled together or, for example, placed in a container where the heat cannot dissipate.
Waterborne Varnishes
Crystal Water Varnish
Crystal Water Varnish
Crystal Water Varnish is a gum arabic varnish that adds luster to a watercolor painting and saturates colors. It adds gloss to the surface of watercolor paintings and allows the glazing of watercolors without lifting the paint underneath. Use it over darker colors to increase the color depth and saturation. It is based on recipes used by watercolorists of the 18th and 19th centuries.
Contains natural ingredients. Does not contain organic solvents. It can be thinned with water.
Available in 8 fluid-ounce (236 ml) bottles.
Lac Water Varnish
Lac Water Varnish
Lac Water Varnish is a natural resin varnish that can be used as a fixative on watercolor and tempera painting to isolate painting layers in glazing techniques and enhance color saturation. It can also reduce the absorbency of traditional gesso and chalk grounds. It is based on a recipe used by watercolorists of the 19th century.
It can be used in combination with the Crystal Water Varnish to “fix” the paint layer before applying Crystal Water Varnish.
Contains natural ingredients. Does not contain organic solvents. It can be thinned with water.
Available in 8 fluid-ounce (236 ml) pump spray bottles.
Conservar Varnishes
For help selecting the right varnish for your artwork, please Selecting the Right Varnish for Your Painting.
