Functions of a Varnish
Varnishes can assist the art work in several ways. They can be used to change the surface gloss, making the surface more matte or higher gloss, or to provide the various areas of a painting with a more unified finish. They can also be used to increase color saturation. Varnishes offer protection for the underlying surface and allow for ease of cleaning of the painting or object. They are also often used to consolidate art work, in a similar manner to a fixative for charcoal or pastel. Some varnishes offer additional protection in the form of Ultra Violet Light Stabilizers, which dissipate UV radiation before it can contact the artwork where damage may occur. These varnishes are especially useful for materials that are fugitive in nature, such as dyes, but will not render them completely lightfast. The thicker the film of varnish w/ UVLS, the greater the protection afforded.
Requirements of a Varnish
Varnishes should be removable to allow for cleaning without damaging the underlying surface. The use of 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, yet be hard enough to resist retention of grime and dust by providing a nontacky surface. Depending on the substrate and environmental conditions, it must be formulated with the correct porosity to either allow moisture to pass through or provide a moisture barrier. It should have good chemical and water resistance. Over time it should resist discoloration caused by factors like humidity, heat and visible and ultra violet (UV) light sources. Finally, the varnish must possess excellent clarity, without discoloration or fogging.
Aesthetics of a Varnish
In all cases, varnishes serve an aesthetic function, whether desired or not, due to a difference in the refractive index between the varnish and what is underneath it. A "perfect varnish", that does not alter the appearance of the painting, is often requested, but has never been fully achieved. Therefore, varnish is most successfully used when it compliments the painting. Practice and experience will provide an understanding of how varnish affects the look of a painting. Varnishes are offered in a range of finishes, from gloss to matte, to allow the artist control of the sheen. Different finishes of the same brand can usually be intermixed within each product type, or used sequentially, to achieve any desired level of gloss.
Types of Varnish
A recent conference at the Canadian Conservation Institute was dedicated to the discussion of the current state of the art and science of varnishing for the paintings conservator. The symposium covered traditional natural varnishes such as Dammar, Copal, Mastic and newer synthetic varnishes with names like Laropal K80, PVAA/AYAB, PVA/AWAB, Mowilith 20PVA, Ketone N, Arkon P90, Regalrez and Polybutylmethacrylate. These materials were reviewed by the material scientists and conservators for their suitability as a varnish for modern and earlier works of art. Although most of the discussion of these varnishes and their viability as coating for works of art are beyond the scope of this paper, some discussion of the earlier varnishes and some of the new systems helps put the topic of varnishing into better perspective.
The most important traditional varnish is dammar. It is the only traditional coating system that is still recommended as suitable for a work of art. Other resins, such as copal or mastic, although unfortunately still in use, suffer from cracking, 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 greatly affecting the paint layers below.
The search for a better alternative has moved to the newer synthetic varnish systems. Quite a deal of discussion has recently centered around low molecular weight varnishes, such as the new varnish by Gamblin, GamVar, and high molecular weight (HMW) varnishes such as our MSA varnish. A low molecular weight varnish will tend to have greater gloss, higher refractive index and will provide greater saturation into the surface, due to the smaller molecular size, than high molecular weight varnishes. On the other hand, HMW varnishes tend to offer a better protective surface, have greater elasticity and more resistance to blooming.
Although some new work by René de la Rie, Head of Scientific Research of the National Gallery of Art, has suggested various alternatives, we continue to prefer the polybutylacrylate systems, Golden MSA Varnish, which have so far proven the most durable and lightfast, and maintain their removability. Our other varnish, Golden Polymer Varnish, is unique in that it offers a waterborne varnish which meets the criteria of remaining removable and having good visual properties, while freeing the user from hazardous solvent exposure. In terms of film toughness and permeability, this varnish provides an intermediate level of performance compared to the MSA Varnish. Rigid supports allow the use of much harder varnishes. This is especially important when applications involve functional use of the artwork, as in furniture or floor designs. Often the varnish of choice in these applications is a polyurethane because they provide some of the most nonporous and toughest films available. They often fail the rule of a removable coating, but this may have to be accepted, depending on the application. Polyurethanes which have been available the longest, the aromatic type, are prone to yellowing. However, recent innovations have provided polyurethanes that do not yellow. These are of the aliphatic type. They can be purchased as waterbased or solventbased products, in both single and two part systems.
Varnishing Acrylic Paintings
Some practitioners of conservation and art instructors recommend that paintings done with acrylic emulsion paints not be varnished, because of the potential difficulty in removing the varnish without affecting the paint film. Our research and experience indicate that with the right varnish and technique, varnishing of such paintings is advantageous and risks are minimized. Acrylic paint, being a thermoplastic polymer, tends to soften under conditions of high temperature and/or high humidity. This makes it more vulnerable to retention of dust and dirt particles. A varnish that is harder than the paint will reduce this, while providing a sacrificial layer for cleaning. However, it is critical that the varnish maintain good flexibility if the support for the painting is also flexible, as with canvas or paper.
In order to protect the paint film if varnish removal is required for restoration purposes, we recommend that an
intermediate layer of an isolating medium be applied. An isolating layer is a transparent film that physically separates the underlying layer of paint or other medium from the varnish to be applied. When a solvent is used to dissolve the varnish, the isolating layer will prevent it from reaching the paint layers, where damage, mostly in the form of color pickup (solubility), could occur. The isolating layer is also of critical importance when applying a matte varnish over an absorbent surface (such as a stained surface) to prevent a cloudy or "frosted" appearance from occurring. This frosted appearance results from the varnish and solvent being absorbed into the support, while the matting agent remains exposed on the surface, where it appears as a white solid. Golden Soft Gel (Gloss) thinned with water is a suitable isolation coat. It provides adequate leveling and foam release.
The most critical part of achieving success with varnishes is the application. Unfortunately, varnishing is considered as an afterthought, or is rushed through to finish and ship the artwork. For successful application, the user must be thoroughly versed in proper techniques, as well as the inherent properties of the varnish. It is very important to spend some time experimenting with the varnishes on test pieces, in order to become familiar with the products.
James Bernstein, Conservator of Fine Paintings, offers the following method for brush-applying varnish: The technique I use for brush varnishing proceeds as follows. A varnish solution of appropriate viscosity is prepared and then transferred to a low profile, widemouth, weighty (tip-proof) vessel. The vessel is filled with only a shallow volume of varnish, so that the solution will wet only the lower tip of the brush (1/4 to 1/3 the total length of the bristles).
Prior to proceeding, a varnish application strategy must be determined. For this, the boundaries to be covered with each brush dip of solution need to be envisioned. At times, the varnish is applied in square or rectangular sections, following a grid of overlapping regions. Still other times, varnish is applied in freeform sections, following compositional features or outlines.
Before dipping and brushing, estimate the amount of coverage possible for even distribution with each dip. When proceeding, always place the loaded brush in the middle of the section to be covered. The solution is then spread out evenly saturating the entire section. The next dip is placed in the center of the next area to be covered, not directly adjacent to previously varnished area. After filling the present section, the still wet application is often finished with quickly brushed, low angle strokes, lightly overlapping the wet varnish across the transition edge where it meets the previously applied, partially set varnish field. The painting is varnished thusly, going from section to section until complete.
For spraying varnish, which we feel is generally the best method of application, Mr. Bernstein recommends: Always pretest spray settings and solutions to observe the handling and forming of the varnish before attempting to spray any art. Once adjustments are made, spraying is begun at a far corner of the painting, continuing across the surface in an uninterrupted linear pass. Constant distance is maintained (e.g. 1014 inches) and spraying proceeds past the outer edge of the painting, where a turn in direction takes place for the next, slightlyoverlapping, parallel pass of varnish. Spraying continues in this manner until the entire surface is covered. For subsequent varnish applications, the spray orientation may be switched by 90 degrees (e.g., horizontal passes for the first coat, vertical for the second, and so on) to ensure uniform distribution. 1,2
The above advice is the product of extensive experience, training and knowledge of materials. Professional conservators are often expert in the field of varnish application and have the equipment to do the job right. Having a conservator perform the varnishing of paintings is an alternative worth considering, especially for works of special importance.
1 Varnishes, Authenticity and Permanence Colloquium, September 1920, 1994
2 A Review of Varnish Application Fundamentals, 1992 AIC Paintings Specialty Group Postprints, American Institute for Conservation of Historical and Artistic Works, 1400 16th Street N.W., Suite 340, Washington, DC 20036
The following information is provided to offer insight to the varnishing process. While the virtues of varnishing are numerous and generally understood, often times the specific "how to's" to insure successful varnish application are lacking, or simply not well understood. The goal of this guide is to supply this particular information. The application of a varnish should never be considered as merely an afterthought to the creative process. Instead, one should realize that the selection of the varnish, as well as the application of such must be carefully considered. A thorough understanding of the entire varnishing process is paramount to avoid
Prior to actual use, it is very important to experiment with Golden varnishes on test pieces to become aware of how they perform and how they alter the surface appearance of paintings. For best results, apply to a test piece that is similar in composition as the artwork to be varnished. This will help ensure that all variables are accounted for, and a successful varnish application will be achieved.
Only intended for acrylic paintings, do not use on oil paintings.
For future conservation and varnish removal purposes we recommend the use of an isolation coat prior to varnishing. An isolation coat is a permanent, nonremovable coating that serves to physically separate the paint surface from the removable varnish. This will help protect the surface if the varnish is ever removed and make future cleaning and conservation easier to avoid working directly on top of the pigmented part of the work. Therefore, even if painted with delicate washes or large areas of colors that could potentially bleed, a clear barrier would safely cover the painted surface. It will also seal absorbent areas, which will result in a more even application of the varnish. In the event that no varnish gets applied, the isolation coat serves to decrease the water sensitivity of the paint surface, affording protection during routine cleaning/dusting.
Given the current state of conservation science, we feel the use of an isolation coat provides the most protection. However, isolation coats are also significant and permanent additions to a painting and inevitably will cause changes in the painting's surface qualities. Whether these changes are acceptable is an aesthetic decision that each artist needs to make after sufficient testing. In addition, since it is nonremovable, any mistakes or problems during this procedure cannot be easily corrected and there is always an element of risk that needs to be considered. We strongly encourage the artist to practice these procedures thoroughly so they feel confident and become familiar with any unforeseen problems. If you have any questions or concerns regarding the proper use or application of an isolation coat, please call Golden's Technical Support Department at (800) 9596543.
For brush application, the appropriate isolating medium can be made by diluting Golden Soft Gel Gloss with water (2 parts by volume Soft Gel Gloss to 1 part water). If a spray application is desired, a 2:1 mixture of Golden GAC500 to Transparent Airbrush Extender can be applied with an airbrush, touchup spray unit or commercial spray equipment. The absorbency of the surface will dictate the number of isolation layers required. For relatively nonabsorbent surfaces, as is the case with a uniform paint layer, one coat brush applied or two coats spray applied are recommended. For more absorbent surfaces, which tend to be very matte, it is recommended to apply sufficient isolation coats to achieve a satin sheen on the surface. This may require two or more brush applied coats or three or more spray applications.
The isolating layer is of critical importance when applying a matte varnish over an absorbent surface to prevent a cloudy or "frosted" appearance from occurring. This frosted appearance results from the varnish and solvent being absorbed into the support, while the matting agent remains exposed on the surface. While we have carefully selected the matting agent that is in Golden varnishes to be as transparent as possible, it is still a dry particulate material. When the matting agent is deposited onto the surface, and is not a part of a continuous varnish layer, it appears as a white solid. If varnishing watersoluble paints, including watercolor, gouache and tempera, the isolation coat must be sprayed on in very light layers to avoid solubilizing the paints, which could cause loss of distinctness of the underlying image.
Make sure paints are sufficiently dry. For acrylics and other waterbased media, if the painting is composed of thin layers, waiting a day or two before applying the isolation layer, followed by another two days to a week before varnishing, is recommended. If there are thick, impasto areas of acrylic paint, wait a week or two before applying the isolating layer or varnish. Oil paints generally require six months to a year drying time prior to varnish application. Next, make sure the surface the varnish is to be applied to is clean. It should be free from dust which could affect appearance of the varnish. If the isolation coat (over an acrylic painting) has cured for more than 23 weeks, the surface should be washed with water using a soft, clean cloth in order to remove surfactants which may have migrated to the surface, as these can interfere with adhesion. Allow the surface to dry completely before varnishing.
Another consideration is the ambient conditions of the work area. Ideally, the temperature should be above 65 F and below 75 F, while the relative humidity is between 50% and 75%. Excessive humidity or cool temperature may result in bloom, a whiteness or opacity resulting from moisture trapped between the varnish and paint layers. If the surface of the piece being varnished is warmer than the varnish applied, the varnish will become thinner in viscosity upon application. This may result in unexpected dripping or sagging, particularly if working vertically. Likewise, if the varnish and surface are relatively cool, but warm significantly shortly after application, the varnish may drip or sag. Prewarming the varnish in a warm water bath can help prevent this.
The type of surface can greatly impact how varnish is best applied. Stained or partially coated surfaces are some of the most difficult to successfully varnish, due to the uneven nature of their application. In areas with a heavier stain, the varnish may sit on top, while sections with more thinly applied paint, or no paint, will allow the canvas to absorb the varnish into the fabric support. This discontinuous surface can cause uneven saturation of the varnish, yielding a blotchy appearance with nonuniform reflectance. Also critical in the application of this sort of surface is the thinning of the varnish and the amount of varnish on the brush. More thinning and the varnish increases penetration. Too much varnish on the brush in one area and the varnish gets absorbed and soaks through the piece. An isolating layer applied before varnishing will provide a continuous surface for the subsequent application of a uniform final varnish layer. It is then possible to match the original surface appearance by lightly applying matte varnish. The nature of the surface must be considered when selecting the finish that is desired. As mentioned in the isolation section, highly absorbent surfaces must have an isolation coat applied before application of a matte or satin varnish. Surfaces that need to be reflective, such as the Iridescent and Interference Acrylics or metals, would require a gloss varnish to maintain the reflective quality. Golden varnishes are not intended for use on furniture, floors or other surfaces where a high degree of physical toughness is required. For applications such as these, the polyurethane family of resins proves most useful.
When selecting a polyurethane, note that aromatic type urethanes yellow significantly, while the aliphatic types do not.
Thinning GOLDEN Varnishes
Golden Varnishes must be thinned before use. This reduces the film thickness applied and the chance of uneven application. It also allows for much greater fluidity of application, which is critical when applying a varnish. If applied in a thick state, the varnishes may show brush strokes and trap foam bubbles. The varnishes have been made thicker for the purpose of maintaining an even suspension of the solids within the varnish. Even slight settling of varnish solids during storage may result in streaking within the dried varnish film.
Thinning GOLDEN MSA Varnish
In theory, mineral spirits, commonly referred to as "paint thinner", should suffice to thin Golden MSA Varnishes, however, they do not always work. "Odorless" mineral spirits should NOT be used because they are not strong enough to be compatible with the varnishes. It is recommended that any mineral spirits be first tested for strength and compatibility with the varnish, by blending them together on a very small scale. This will minimize loss if the mineral spirits do not work. If compatible, they will thin the varnish and maintain translucency. If the solvent is not compatible, the mixture will not become thinner and may even become thicker and more opaque. To help avoid the problem of solvent incompatibility, distilled or rectified white turpentine may be used. Such a grade has been purified sufficiently for artists' use. Other grades contain residual materials that may decrease the archival nature of the artwork.
Thinning GOLDEN Polymer Varnish
Distilled water is the preferred diluent for Golden Polymer Varnish.
While tap water may be used, it may contain impurities such as minerals or bacteria. Some artists thin water borne materials with alcohol. This practice, while sometimes very successful, should be approached with caution. The shorter chain alcohols, like methanol, and ethanol can shock the varnish and coagulate it, making it cheesy or stringy. This practice also reintroduces a more hazardous solvent than simply water. The amount of thinning required will depend upon the method of application. For spraying, a suitable range is from 12 parts varnish per part diluent. For brushing, a ratio of 3 parts varnish to 1 part diluent should yield a mixture that flows on well and allows for leveling and foam release. Satin and matte varnishes tend to be thicker in the bottle than the gloss varnishes and may require additional dilution. When thinning, slowly add the diluent to the varnish while gently stirring. To ensure an even finish, the varnish must be mixed thoroughly. Be careful not to create foam bubbles. Do not shake the mixture. If mixing more than one quart of varnish, a drill with a paint mixing attachment may be used. Operate it at a low speed and be careful not to create a vortex which will pull air into the mixture. If the varnish becomes foamy, let it stand for a half hour or more to allow the foam to escape, then gently stir. When working with a Satin or Matte finish, thin down only the amount of varnish that will be used that day. Storing a diluted varnish will result in the matting agents settling to the bottom, where they may become a tightly packed layer. If this occurs, it may not be possible to fully reconstitute the mixture by stirring.
Applying GOLDEN Varnish
It is preferable to brush or spray apply Golden varnishes. Other methods, such as sponging or rolling, are not recommended, as they may result in problems such as: foaming, loss of film clarity, nonuniform coverage, excessive film build, sagging, or deposition of materials from the application tool.
Use a high quality bristle brush, such as those made by Purdy or Wooster, or for more control and smoother application, a wide thin flat colorwash brush. The Da Vinci Cosmotop Spin brushes are an example of this type. The size of the piece to be varnished will determine the size of the varnish brush. Work from a shallow container to help control brush loading. The varnish solution should wet only the lower 2530% of the length of the bristles. It is always best to apply the varnish on a horizontal surface in order to minimize running or sagging. If vertical application can not be avoided, as with a mural, it is extremely important that the varnish be thinly applied. In either case, it is better to apply two or three thin coats with sufficient drying time in between, rather than one thick coat of varnish. The latter will take longer to cure, staying soft for some time, and could result in drips or a cloudy film. Apply the varnish in a manner which allows it to be brushed out to the most uniform, thinnest film possible. Mentally divide the work into regions to be covered by each loading of the brush. These may be based on a systematic gridlike sequence or may follow natural boundaries of the piece.
Maintain an even application by working from the center of each region outward. Lightly overlap into still wet, adjacent sections. When applying a satin or matte varnish, never apply more than two coats. If multiple coats are desired, start with the gloss varnish to build up and establish the multiple layers, then finish with one or two coats of the satin or matte finish. A thick film of these reduced sheen varnishes will result in film cloudiness, and loss of clarity.
The best way to achieve an even coating of varnish is to spray apply. This is particularly true for impasto surfaces. Spray application is required for any surface where the paint film is fragile, such as gouache, and should not be touched by application tools. Spraying is also a useful technique for creating a matte surface. The size of the surface to be sprayed will determine the best type of spray equipment to use. These varnishes can be sprayed from an airbrush, airless or air pressured spray equipment, or refillable aerosol equipment. In preparation for spraying, make sure all equipment is free of dirt. Work in an area free of dust and dirt and keep work off the ground when spraying. Spray three to four light even coats instead of one or two thicker applications, allowing enough time for drying between coats (14 hours, until surface is tack free). Release the spray trigger if the motion of the airbrush is stopped during application in order to avoid an uneven build of varnish in one spot. Maintain uniform distance from the surface, and avoid the tendency to use an arcing motion. Make straight passes across the work, changing direction once the spray has cleared the edge of the piece being varnished. Slightly overlap the spray pattern with each pass, until the entire piece has been covered. To aid in achieving a more even application, turn the painting 90 degrees in order to apply the subsequent coat perpendicular to the previous one. A typical spray application lays down a film only 1/6 to 1/4 the thickness of a brush coat application. If maximum protection is required of the varnish layer, apply multiple coats. This is especially important when protecting colorants that are not inherently lightfast, as the thicker the total varnish film, the greater the protection from ultraviolet radiation. Because it is not recommended to apply several coats of a satin or matte finish, underlying layers should be established using a gloss varnish.
Murals and Architectural Applications
Any paint or topcoat applied to a building, including interior or exterior walls, is considered an architectural coating and subject to regulations limiting the amount of VOC's (Volatile Organic Compounds) a product may have. Murals painted directly onto these surfaces, therefore, will fall under the same guidelines and all paints, mediums, and varnishes being used will need to comply with the same rules. Containers that are 1 Liter (1.05 Quarts) or less in size, however, are currently exempt from these requirements.
Murals painted onto canvas, panel, and other supports
Clean all equipment immediately following application. If tools are wet, Golden Polymer Varnish can be removed with water. Ammoniated glass cleaner or a 1:1 solution of household ammonia to water may be use if the varnish has set. Golden MSA Varnish should be cleaned from tools with the same solvent used for thinning, followed by soapy water wash and clear water rinse.
The isolation coat should cure for 1 day before varnishing. When building up multiple coats, allow for 3 6 hours in between coats. Gently inspect the surface for tack, which may signify that the coat is not sufficiently dry. Let varnish cure several days before packing or transporting art. During transportation and storage, avoid contact of the surface with packing materials, including glassine, bubble wrap or any other plastic. NEVER STACK PAINTINGS, whether varnished or not.
Care and Storage
As Golden Varnishes are removable, it is important that they not be painted over. Paint applied over the varnish would also be potentially removable, and would pose a difficult problem in conservation or restoration attempts.
|Milkiness or opacity occurs in varnish layer||
|Reflectance is not uniform||
|Brush strokes remain||
|MSA Varnish will not thin down||
|Pebbly or textured surface when spraying||
|Sinking in and not developing sufficient gloss||
|Surface is too glossy||
|Surface is too matte||
The above information is based on research and testing done by Golden Artist Colors, Inc., and is provided as a basis for understanding the potential uses of the products mentioned. Due to the numerous variables in methods, materials and conditions of producing art, Golden Artist Colors, Inc. cannot be sure the product will be right for you. Therefore, we urge product users to test each application to ensure all individual project requirements are met. While we believe the above information is accurate, WE MAKE NO EXPRESS OR IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, and we shall in no event be liable for any damages (indirect, consequential, or otherwise) that may occur as a result of a product application.