Up until now, artists have employed a variety of varnish coatings to protect their work. For the most part, these are urethane-based coats that served as the best graffiti protection solution prior to the advent of wax-based sacrificial coats.
When the use of a permanent coating was the only way to protect a mural from graffiti damage, the laborious practice of its removal was unavoidable. Further, after a few cleanings a reapplication of the varnish is necessary. The sacrificial coating is washed off with hot water--paint and any other material on top of the coating surface coming off with it--and then reapplied, normally by a contractor.
This breakthrough further points up other disadvantages of the permanent coatings. First, they have a tendency to gather up dirt. Particles from the air that gradually builds up an obscuring layer of scum that is increasingly difficult to remove. Second, they discolor over time, sometimes unevenly so that a streaking effect begins to appear. Third, most gradually peel off. A fourth effect that occurs with some products is their lack of breathability, which results in the trapping of water vapor and condensation in certain walls. The overall verdict is that urethane or rhoplex based varnishes are good initially, but after 2-10 years become labor intensive or destructive to the mural.
Enter Soluvar.
Soluvar has been used strictly as a varnish for easel paintings in the past. Used by itself as a coating for murals, it does not offer sufficient graffiti protection to compete with the currently preferred varnishes. In conjunction with a sacrificial coating, however, this is no longer a limitation. The stability of Soluvar thus becomes a significant factor, in my opinion making it the varnish that muralists should be using whenever sacrificial coatings are going to also be used.
The following in-depth description of the Soluvar product and its properties may be on the dry side for many readers, but for artists and technicians the information is of great importance, and deserves special attention.
Soluvar is a thermoplastic resin made of pure acrylic monomer crystals then suspended in V.M. & P. Naptha mixed with toluene. The resins are manufactured by Rohm and Haas, and are used in the following proportions:
1. Acryloid B67--90%
2. Acryloid F10--10%
3. V.M. & P. Naptha--85%
4. Toluene--15%
Soluvar remains soluble in Naptha or other thinners of similar solubility parameters in perpetuity. There is a strong resistance to crosslinking with the acrylic paint over which it forms a protective coating. If mixed with pure solvents, it remains waterclear, and provides an unusually hard and water-reflecting surface.
Acrylic emulsion paints such a Liquitex and Nova are based on Rhoplex, an acrylic emulsion material. As an emulsion, the resins are suspended in both solvents and water. When the water dries, it tends to leave microscopic voids that tend to absorb smog, dirt and any water-borne substances. Thus, an uncoated mural painted with acrylics is absorbant to a degree that, left unprotected, encourages accelerated breakdown of the surface.
Soluvar as a brand (developed and marketed by Liquitex) is the most compatible coating for an acrylic mural. It is used in all major museum and conservation laboratories as a preferred varnish for both acrylic and oil paintings. The Soluvar product has a high gloss, and can also be matted in a variety of ways. It should be applied to an uncoated gel, unless the present varnish is Liquitex. Otherwise, older murals, prior to coating with Soluvar, must have previous varnish stripped.
I spoke with a laboratory representative from Liquitex about the value of applying a coating of their varnish prior to Soluvar application. In fact, the reason is legal protection: if a Soluvar coating is removed improperly, causing damage, it could be difficult to demonstrate fault in the context of a lawslit. This is understandable enough, but the problem for muralists is that the Liquitex varnish is prone to discoloration and deterioration.
Soluvar should therefore be used only on an uncoated acrylic mural for best results. If a prior coating of Liquitex is already there, fine. But one should not apply Soluvar over urethane-based graffiti coatings.
Soluvar, when used on an acrylic mural, will seal the porosity of the paint while augmenting the reflecisity of the re-active index. It provides superior water shedding properties. Also, it may be removed easily with low-grade solvents.
An optional feature of Soluvar is that, when applied thickly, it can function as a sacrificial graffiti barrier. Thus, when spray paint is applied, the Soluvar can be washed off, removing the spray paint with it. Heavily sprayed paint containing a large proportion of toluene can, however, partially dissolve and penetrate a Soluvar barrier, so there remains a potential for damage in this scene. If graffiti is a problem, therefore, Soluvar should be used as an intermediate coating with a sacrificial coating going on over it.
I want to know how to treat plywood or other panels to use for murals to be displayed outdoors. I am involved with school and other limited budget community projects, so l want to know what affordable materials I can use to extend a panel's life.
Wood, particle board, masonite, wafer board--these are the least expensive materials that can be used outdoors to provide a solid, portable mural surface. Unfortunately, these materials are unstable and tend to disintegrate swiftly. Nonetheless, you can improve the stability of Extenor Grade materials by consolidating them with added resins. Some of the consolidants are very toxic, but a few can be used safely. Unfortunately, the best consolidants are also the most toxic. Masonite is not a good materials for outdoors, and should simply never be used. Fiberglass panels (rough surface) are ideal if coated with Rhoplex and then gesso. Plywood can be coated with polyester resin (somewhat toxic), and then one or more layers of glass cloth of matting. The plywood, waferboard or particle board should be put in a sealed room with a powerful dehumidifier for several days prior to coating in order to evacuate ALL moisture from the wood. Thinned Rhoplex is the least toxic and easiest method to seal these surfaces. It should be applied to all sides, but particularly the ends. Several, increasingly thick layers should be applied. The wood may also be treated like a boat--a marine sealer, undercoat and finish coat may be used. By thoroughly coating all sides, water is denied entry that would swell the wood and ruin the art. Of course, it is always a good idea to consult a person knowledgeable about these materials before plunging ahead on a project so that you maximize the likelihood of a satisfactory outcome.
When is it appropriate to use Soluvar?
Soluvar, or it's generic equivalent, is the only varnish that will not ultimately destroy an acrylic mural. It is reversible (dissolves in paint thinner) and does not cross-link with acrylic or oil paint. For this reason it is widely used in conservation labs as a final or isolating varnish on acrylic and aged oil paintings. It produces a hard, grossy surface that can be adjusted or even matted by thinning, dry-brushing, or over-spraying to fog the surface (or just add matte soluvar to dull the surface).
Soluvar is far less porous than acrylic varnish and so can create problems when used on a mural on a damp wall, since the wall moisture mixed with sunlight and temperature fluctuations will tend to push the paint off the wall. Water vapor is restricted by the varnish from passing through the relatively porous paint.
The reason I discourage the use of acrylic emulsion varnish on acrylic murals is that the porous acrylic varnish absorbs smog, smoke, dirt, algae, etc., permanently. In addition, the clear acrylic film causes ultra-violet rays to oscillate within it's thickness, causing it to break down and powder very quickly.
by Nathan Zakheim.
(Published originally in the MCLA Newsletter, v. 4, ns. 1,2, 1992).