Making Your Mural Last (original) (raw)
Particulars of Our Mural Wall
We have an ideal wall surface. I won't just gloat—I've also included information applicable to other circumstances. Our wall faces north, and being in the northern hemisphere, that means we have very little sun exposure and therefore a longer mural life expectancy. Also, our wall has an air-conditioned (i.e., dry air) store on the other side, not soil or other moist material. This saves us from the problems of moisture seeping through the wall. There is very little car traffic nearby, therefore very little tire dust. There is some dust in the air from the "sanders" of the adjacent streetcar's braking system. San Francisco has few coal or oil heating systems, meaning greasy soot is not a problem for us. Overall, our only real worries are the wall's settling (increased during earthquakes) which cracks the thin layer of stucco, and graffiti or vandalism.
It's tempting to assume that all the problems of the wall underneath your mural will simply disappear as the original wall surface itself disappears from view. They will come back to haunt you. I will explain what I know about the best way to handle what is behind your own mural, but my personal experience has mostly been with new surfaces made of calcium carbonate materials (cement, stucco, cinderblock, cement block). I know a lot more about what protection to put over a mural, so a lot of this article is about varnishes.
Wall Structure
I don't think it's possible to learn about all possible issues with wall physics and chemistry (as I did, of course, with varnish), so this article gives details about the surface of our wall only, which might remind you of considerations that you otherwise might not think to consider.
The wall we painted had an old, concrete section that was sandblasted in preparation and covered with a new fine-grained stucco finish. It also had a larger, new (also stucco) section that was still being built while we were finishing up the mural design. The new section of the wall is cement block covered with the same stucco. [After four years, cracks in the shape of the block outlines have developed from settling.] The wall goes up higher than the roof line and therefore has an exposed (flat, stucco) top about ten inches across where rain can seep into the stucco, especially where there are cracks.
The building location is, unfortunately, quite close to or even on top of an old stream bed that was filled in long ago but continues to settle each time there's a tiny earthquake (or a heavy building built on it). As the building settles, hairline cracks are appearing in our mural. Where those cracks meet the top edge of the wall, half-inch crevasses were appearing already when the wall was less than a year old. If you want your mural to last, you should consider what structural issues are pertinent to it before you even begin to paint. We didn't think about this and are struggling after the fact to keep holes patched and hairlines monitored. We are considering revarnishing the cracks as they develop to keep a continuous, closed surface as long as possible. A narrow smear of clear silicon caulk covered with a dab of varnish might be good too, depending on how quickly the crack widens, but we haven't tested either idea.
Wall Preparation
We had a wall chemist (Hap Hazzard—that's his name—of Fregosi Paint in San Francisco) come look at the wall early in the wall construction process. He explained that the chemical mechanism causing the old paint to peel (before it was sandblasted) was based on moisture in the wall intruding over time. Water vapor or liquid water, either of which can come through from the back of the wall or gets in through the top or cracks in the front, reacts with the calcium compounds in the stucco or cement to form alkaline calcium hydroxide. This base (high pH) solution deteriorates the paint and its bond with the wall. If you have ever used trisodium phosphate (TSP) in water to clean old paint off metal fixtures, you have seen how an alkaline (basic, or high pH) solution deteriorates paint quickly. This is what happens in a wall made of cement, concrete block, stucco, or other calcium-based materials.
This information made me happy at the time, because I was asking Hap about how easily the old paint would come off the wall. Safeway, the building owner, hired a hazardous materials removal crew to strip the lead contaminated old paint off, down to bare concrete. They then had the renovation crew cover that with the same stucco used on the new portion of the wall. The process was made easier by the lye-weakened bond between the old wall and the old paint. (Was this the mudane inspiration for that profound old cowboy song?)
Unfortunately, I didn't think ahead about how we would prevent that same effect from happening to our mural. The proper thing to do, given the luxury of painting a mural on a new surface, would have been to treat it with a mild acid, such as dilute (watered-down) muriatic acid (another name for weak hydrochloric acid, available in any hardware store) or, in a pinch, use dilute distilled vinegar (acetic acid). This would have decreased the pH (reduced the alkalinity) of the wall, which in turn would counteract the formation of calcium hydroxide in the wall, thus saving us from much of the bond-weakening effect.
Since we did not apply that treatment directly to the new, unpainted surface, we are now faced with a more urgent need to keep moisture out of the wall. For the first few years this will be easy, since we sealed the top of the wall and the store inside doesn't generate moisure from behind (they are air conditioned). However, as cracks form in the top and front of the wall, we may have efflorescence (bubbling) in our paint as little pockets of moisture detach the paint from the wall. I think I'll go put a little varnish on those hairline cracks tomorrow!
The only other issue we had with surface preparation is that the same water-based primer used for the wall was used for the little steel plates that tie the roof into the wall. After a few months of mural painting, rust started seeping through the paint on these little squares of metal. We had to pause most of the way through our mural to cover those plates with an isolation coat of red-oxide industrial metal primer, and then repaint those pieces of the mural. Of course we should have used the primer (or one like it) on the bare metal before anything else was painted on it, but the isolation coat may work. [Note: as of four years later, the isolation coat is still working, despite our laziness in applying it over our first water-based acrylic layers.]
The Benefits of Varnish
In this report, I have used the general term 'varnish' to mean all kinds of clear protective coatings.
Fade protection, stain protection, graffiti protection. These are the three reasons you will probably want to cover your mural with varnish, either shortly after completion, or section by section of your mural, depending on factors I will discuss later.
The most common question about fading is How long can I expect my mural to look good? Assuming it looks good to begin with, here is my studied opinion on the matter: As a general rule, murals painted house paint or stage set paint last a few years before they begin to fade; murals painted with good acrylic mural paint last dozens of years; murals painted with watercolors, tempera or fingerpaint will begin to deteriorate immediately; murals made with carefully set tile mosaic will last thousands of years (I've seen some nice ones that old!). If it's indoors or in a cave, it'll last a lot longer. If the mural wall traps moisture or faces the sun, you face a challenge: it will probably either fade or fall to bits (or both!) before you are done appreciating it. This decay may be put off decades if you have the patience and commitment to take every available precaution. If it's really important to you that the mural last forever, choose a wall that is protected from moisture and weather and sun and earthquakes, vandalism, politics and grime—in other words, a mural in your mind.
The sun's rays, both in the ultraviolet (UV) and the visible parts of the spectrum, can deteriorate and fade your mural. There are three types of deterioration which result in fading: pigment breakdown, binder breakdown, and varnish breakdown. The first, pigment breakdown, is a chemical change in the pigments. The best protection against this is to use well formulated and richly pigmented mural paints. We used Nova Color acrylics. The second, binder breakdown, can also be minimized with the right paints, but eventually, the medium that holds the pigment in place will probably dry up and become "dusty" as the medium crumbles on a microscopic level. This can be slowed by the use of a varnish protective coat. It can also be corrected, even undone and restored to its original brilliance through art conservation techniques (see resources—Nathan Zackheim's article on consolidants). Most varnishes protect the surface of the mural from deterioration due to those nasty rays from the sun. The third kind of "fading" is actually due to the varnish—rather than the mural paint—becoming cloudy, thus obscuring the mural's surface. This happens when UV rays break up the varnish itself, possibly by internal reflection within the varnish layer, as purposely occurs in an optical fiber. (See Nathan Zackheim's dramatic piece on the problems with urethane.) It appears that the best way to avoid this problem is to avoid permanent urethane varnishes on walls that get a lot of sun exposure. Other types of varnish may eventually suffer the same deterioration and clouding, but are easier to 'consolidate' when crumbled and, most important to art conservation, are much easier to remove than urethane. New paint over urethane also has limited adhesion, in case you plan to paint over the mural (with another?) some day.
Stain protection is just a simple matter of putting a protective coat between the sources of potential stains and the mural itself. If the stain can't be removed, then the varnish probably can (unless you used urethane) taking the stain away with it. Some stains are left by graffiti that can't be fully removed, either because the graffiti is somehow especially potent or because of a long delay between when the graffiti comes calling and its attempted removal (the marker or spray paint will cure and become more permanent).
While we were painting, more people asked us how we'd handle graffiti problems than any other question. While standing in front of the mural, I'd rather talk about the art or the organizing or the community, but since mural protection is largely a matter of dealing with graffiti, I have devoted much of this report to that aspect.
On a mural that is within arm's reach, the best method of protection against graffiti is to not get graffiti on your wall in the first place. This is not a joke, and may be easier to do than you think. Think about how you can develop for yourself a friendly, hip or mutually respectful reputation with the people in your area who either create graffiti or know those who do. This may be as simple as welcoming them to your dedication party or publicly documenting your devotion to the mural in a way they can relate to.
When I once saw some kids writing on the partly-painted wall, instead of getting belligerent, I asked them if they wanted to see our mural design and invited them to help paint it. They were impressed and friendly, but they didn't actually end up helping to paint it. I also stopped by the local skateboard shop and struck up conversations with kids about how they could help paint it. I also told them that if they "know any graffiti artists" they should encourage them to paint our on-site supplies storage bin with some "dope pieces." (Translation: 'dope' is a slang adjective meaning 'really good' and 'pieces' are large, elaborate works of graffiti.) By this method, our wall, always a target before the mural project began, had few "tags" (small) and no "pieces" during or after the mural painting. I have seen murals that, because of their content, attracted more than the usual graffiti. When you design your mural, assume that nasty or controversial subject matter will attract graffiti. This is not an admonition against controversial subjects, just a recommendation that you evaluate and plan how to keep it clean. This could mean the difference between a few months and a few decades of exposure and appreciation for your public art.
Also, tags attract tags, and if you remove them quickly, it warns taggers not to waste their time.
Graffiti-related advice could be a whole book, but before I'm tempted to get into any more sociopolitical issues, let's just assume you want to be able to easily remove any marks or uninvited additions to your mural. In that case, what you should do is apply a good varnish. Graffiti will always create extra work for you, but with a good varnish coat, your work will be minimal.
Choosing Among Varnish Products
There are at least four kinds of varnishes that stand a chance of protecting your mural. Two are urethanes: water-based urethane and one based on petroleum distillate solvents. The other two are waxes and certain acrylics. Some varnishes are "permanent," notably the urethanes. Others come off when you apply solvents or heat to clean away graffiti. The latter are referred to as "sacrificial" varnishes.
URETHANE: Though commonly used by municipalities and other large institutions to protect uniformly colored surfaces and masonry expanses, under most conditions urethanes really should not be used by muralists. A long, passionate entreaty, by art conservator Nathan Zackheim, against urethanes can be seen at the LAMurals web site. The main arguments against urethane are three: First, it's really not permanent after all, especially when exposed to direct sunlight on a daily basis or if there's moisture seeping into the wall from behind the mural. Then there's the occasional problem of "ambering" (darkening or yellowing) that most urethanes have to some extent, even the ones that claim otherwise. Lastly, a urethane covered mural can be impossible to repair after it is damaged by any of those processes. (The building owner shouldn't like urethane either, since all future attempts to apply any coatings whatsoever for the life of the wall are compromised—unless the urethane is sandblasted off, nothing will bond securely.)
If there's no moisture intrusion, no direct sun, the mural is temporary, the wall is slated for demolition in thirteen years, you have lots of malicious, airbrush-wielding enemies, and you can get free urethane with low- or non-ambering specs, then by all means, use it. It's really good at stopping pollutant corrosion, standing up to multiple cleanings with heavy solvents, and giving that nice "wet look" glossy finish to the wall.
WAX: Plenty of large instutitions use this protective coating as well. Applied with spray equipment, it requires a reapplication after each graffiti-removal incident. The removal is done with specialized equipment, too. A hot water (up to 190 degrees Farenheit), high pressure (up to 75 psi) cleaning washes off the wax, which takes the graffiti along with it. This is usually arranged through a maintenance contract with the company that sells the wax coating.
If you and the other muralists in your neighborhood (or you and the school district) have formed an Association big enough to handle a regular inspection and maintenance routine with your own specialized equipment or on contract, then wax is a great protective coating. It allows removal for restoration, it blocks out grime, and it is hazardous to neither you nor the mural.
The LA Murals group collaborated on some tests that produced a muralist recommendation for a protective coating called Repello. From the description, I believe it is a wax coating with high temperature removal with a maintenance contract.
ACRYLIC POLYMERS: One technique that comes highly recommended by Zakheim is to use wax over a layer of Soluvar-type acrylic varnish. That is because acrylic on its own can absorb grime, fumes and dust in its pores.
Acrylic polymers also can be good on their own, serving as something midway between a fully sacrificial varnish and a permanent protective film. If your reaction time is within a week, you can remove most graffiti very easily without the varnish coming off, yet if you need to remove a more stubborn stain, with a lot of work you can soften the varnish with solvents and treat it as sacrificial.
The Varnish We Chose The varnish for our mural was some type of acrylic, though the "trade secret" formula and the non-chemist salesfolks made it impossible to get some of the facts. The product we used is a two-part (like many urethanes and epoxies), water-based, acrylic co-polymer. The maker, Graffiti Control Services of San Bruno, California, calls it Graffiti Defenz Sheercoat. You can brush it on, roll it on or spray it on. We got the manufacturer to spray it on for us, in three thin coats, with a fourth coat across the part that is reachable by a person without a ladder (tags happen down low). The finish is not high gloss, but it's shinier and more satin than matte. We also got a pint to brush over cracks and places where we touched up the mural image.
We have experienced only one problem with our varnish: crazing. This is when the gradual shrinkage of the varnish film leaves microgaps, in an alligator-skin pattern barely visible to the naked eye. Sometimes, after cleaning graffiti, there's still a very slightly darker area because of the stains in the tiny cracks. It requires a really close look, but we plan to fix that problem before long by reapplying a coat of the varnish or a solvent that "remelts" and uncrazes the varnish. I hope we get to it before a gray pall appears over the entire mural from repeated graffiti hits over years. It turns out the hits are always in one or two particular parts of the mural, so those are the only areas in danger from this problem. As I implied, there are two approaches to fixing the crazed pattern: apply another coat or two to fill the wee gaps, or—a more enduring option—use a consolidating technique described by Zakheim to redissolve the surface and make a continuous film layer again.
The chances of a similar acrylic polymer varnish working for you depend on the particulars of your wall. Ours has no big source of pollutants or greasy grime. We have lots of free labor from the community that "owns" the mural, passing by each day as they commute home. For us, some sort of semi-sacrificial acrylic layer and quick response cleaning was the answer. We even installed a hidden cabinet with removal materials and instructions so commuters could care for their mural and increase response speed. We also put a layer of regular acrylic medium over each area as we finished painting it and before the mural was sprayed, for short-term protection.
Precita Eyes Mural Arts Center, the most visible mural group in San Francisco, sells and recommends the Sheercoat acrylic polymer that we used, without regard to wall factors, but San Francisco is not an industrially polluted city and Precita Eyes also recommends cleaning your wall immediately upon defacement, so they are avoiding some of the issues. They also say Sheercoat is a sacrificial varnish, which it is not. It is a permanent varnish (though more easily removed than urethane, if you must) which, if used according to directions (including rinsing with water) only needs to be recoated in the event that the old varnish is removed through an unusual circumstance, such as if the wall is scrubbed with abrasives. Precita Eyes recommends four or five coats. According to Graffiti Control Services employee Aaron Smith, Sheercoat requires only two or three coats to be sturdy and effective, especially when applied by brush, which is a thicker coat than spray. Two brushed-on coats are often as effective as three. Spray application may be slightly uneven and therefore up to four coats may be reasonable, though three will do. If a mural is going to be left alone without immediate removal of graffiti, three coats would be better than two, leaving a thicker layer for stains soaking deep into the surface to travel through.
Cleverclean, the solvent sold as a companion to Sheercoat, is touted as nontoxic by Precita Eyes. This is not precisely correct. It contains the ingredient 1-Methyl-2-Pyrrolidone, otherwise known as 2-Pyrrolidinone 1-Methyl, and can potentially be harmful to pregnant woman, having been known to cause as least one human stillbirth (the person removed graffiti for a living, using this solvent), and having been fatal or very harmful to fetuses in animals. The quantities used in properly removing graffiti from a Sheercoated surface probably present no significant hazard, but this information should be available with the product because of the chance of a spill or other accident. I only found that information by research at the medical library. (Journal of Occupational and Environmental Medicine, July 1996, v38 n7, page 705)
Graffiti Control Services will sell varnish directly to a muralist, if the mural is big enough and they do a full spray application as part of the sale. Precita Eyes, probably to protect their market, says you cannot buy directly from GCS, their distributor.
SOLUVAR: Zakheim makes a big push for a type of acrylic varnish that has been used for some time to protect fine art, indoor paintings. You can, with toxicity precautions, cheaply make your own, following Art Mortimer's instructions.
Varnish Caveat
Information I have given here is based on whatever I could glean in my research and applications. The accuracy and consistency of this source information is sometimes limited by trade secrets, nontechnical "folk descriptions" and general confusion about what to call things. Then there's the "buy me" style of promotion that pervades any industry for which the usual clients are bloated public works departments. Every manufacturer wants you to believe their product is "new" and defies the old categories. It's possible, but I think they all fit my four groups: water-based urethanes, petroleum-based urethanes, waxes and acrylics.
A Comparison of Varnish Properties
Here is a quick overview which matches wall properties and varnish attributes.
Ambering or any color change in varnish makes it less desirable, unless active decay, with its time dimension, is part of your art. All commercial varnish sellers should supply potential buyers with specs that include ambering predictions, and there are many which don't amber measurably, so choose among those.
Vapor barriers are almost always worse than breathable varnishes, since most walls have some moisture in them. In the desert or in other dry conditions, this may not be an issue. Vapor barriers, as noted in the urethane section above, can blister and have other problems. But they are potentially useful on surfaces where defacement is frequent, and they are essential on metal-backed murals, unless a high-integrity isolation coat of primer separates the metal from the mural paint. [Note: Do not use water-based paints directly on metal.] Most waxes make no claim about whether they are water vapor barriers, but I can't imagine that wax allows passage of water—wax has been used for millenia to preserve and that requires vapor blocking. Yet I have seen wax varnishes advertised occasionally as breathable. I think those ads are lying, or deceptively playing on the removability of wax. Urethanes are vapor barriers and acrylic polymers are almost all, if not all, breathable.
Thus, the only varnish that will allow new stucco or concrete to completely dry and cure while painted is acrylic. It is best to wait a month for curing and three months for thick concrete to completely dry before painting. But you can cut that shorter if it can continue to breathe. That was no problem with our mural since the breathable acrylic mural paint took five months for us to apply and we did not apply a vapor barrier varnish.
Sometimes you want to add to your mural after it has already been protected by a layer of varnish. The only type of varnish that allows touch-up without first removing the varnish is acrylic, and that requires putting yet another layer of the varnish over your touch-up work.
From the art conservation and permanence perspective, you should always choose a varnish that can be removed. When you finish painting, you may be too exhausted to care what happens to the thing in a decade or two, but if it is a public art piece, people—total strangers—do become attached, and a permanent, restorable mural will matter to them.
Sacrificial varnishes, especially waxes, are best to use if you doubt your ability to get around to a cleaning within a week of its appearance. Most markers and spray paints cure in a week or two under mild weather conditions. If you can't be sure to get to it by ten days, at most, you can wash away the wax along with anything painted on it.
The ease of cleaning a varnish depends mostly on the solvent used to wash off the graffiti, not on the varnish. Despite anything the manufacturer tells you, removing graffiti is mostly a matter of testing different solvents on different pigments. You don't need to use the patented removal solvent that is sold by the varnish dealer. I have never tried it, but I am supposing that wax may also be cleanable (for small tags) with solvents, rather than always and only with a big, hot sprayer machine. I have found that all paint and marker marrings yield to one of two solvents, discussed below, in the section on Cleaning, below.
Toxicity is another factor that we faced in choosing our varnish. Water-based varnishes give off less nasty solvent when they dry. They do give off some. Manufacturers must tell you what protective gear (for example, respirators) is needed to apply the varnish. We chose to avoid the issue and hire a well-prepared team from the manufacturer to do our nasty spray application, necessary due to the large size of our wall. Removing graffiti exposes you again, especially if you have to spray some solvent onto the wall to remove the stain. Always take proper precautions, and don't handle solvents if you are pregnant.
When to Varnish
Always try to varnish when the temperature is moderate and humidity is low. If this is not possible, heat is better than cold weather and humid is better than rainy. Direct impact of rain droplets can ruin any coating. Depending on conditions and surface topography, the Graffiti Defenz Sheercoat acrylic varnish we used is infamous for clouding and foaming when applied by brush. However, the bubbles that cause this cloudy appearance burst and disappear as time goes by. No need to get worried if it appears to be obscuring your mural. By the time it dries it will be clear.
You will have to make the call on whether to apply anti-graffiti coating as you complete each day's work. If the areas you just painted are easy for a defacing spray can to reach in a part of town that seems to have a lot of tags and graffiti hits, you may want to varnish as you go. Although the varnish can be painted over and then revarnished without significant bonding issues arising, a certain glossy dimensionality accumulates as you continue applying coats, so you won't want to change details every day and recoat each. Likewise, you will want to keep the number of final coats of varnish down to four or fewer when the area in question is low and reachable, three or fewer for highter areas. You will be able to tell what sections have been varnished by the satin sheen.
Urethanes and waxes may not be applied until all art in that region is completely painted, since no new paint can go on over them.
Long-Term Issues
Outline of section yet to be completed:
Graffiti Response Time, Over Time
Stickers, Burns, Scratches & Gouges
Abandoned Murals
Cleaning Technique The following are the instructions I wrote for people who come to our mural cleaning cabinet, hidden but reachable through a metal-bar fence near our mural. The parts assuming an involved constituency passing the mural regularly may or may not apply to your mural. Remember, we used Graffiti Defenz Sheercoat acrylic varnish.
MURAL CLEANING INSTRUCTIONS
Let's start with the two most important things:
1. Paint and markers cure in a week or two, so they must be removed immediately after going up.
2. Each time you use this system, try to flag someone who goes by the mural regularly to teach the system to. A larger pool of cleaners will improve response time.
Materials to grab: (if your arm fits through the fence!)
1. scrub brush
2. couple rags
3. Goof-Off spray can [Note: This is a commercial, petroleum-based graffiti removal product available in large grocery stores and most hardware stores.]
4. Cleverclean yellowish fluid in spray bottle
5. water (your water bottle or the backup bottle in the cleaning supplies)
6. protective wear (jacket and rubber gloves)
Procedure:
1. Test which solvent works
..a. Spray a tiny bit of Goof-Off on the bottom edge. If it dissolves the paint, go to Step 2. You can tell it dissolves by heavily colored drips running off. [Note: The reason we try Goof-Off first, despite its water-repellent properties, is that it is much cheaper!]
..b. Try Cleverclean on another bottom edge.
2. Remove graffiti
..a. Spray a small area (then wait 2 seconds for Goof-Off, 5 for Klever Kleenz)
..b. Scrub lightly with brush.
..c. Blot the area just scrubbed with your absorbent rag. Always blot drips before they go down the wall.
3. Remove petroleum smudge:
If you used Goof-Off, there's often a discolored smudge left. Use a light, quick spray of Cleverclean and a clean rag to remove it.
4. Rinse:
Splash a small amount of water on the area just cleaned.
Warnings:
1. If you are pregnant, do not clean the mural. Solvents are dangerous.
2. Do not use solvents in a way which causes you to breathe the spray. Note wind direction before spraying. Although Cleverclean is water-based and studies generally show it is safe (except for pregnant people), Goof-Off is certainly not safe, and neither one should be inhaled.
3. Always use petroleum-based Goof-Off first, as the water-based Cleverclean can dissolve it but not the other way around. Goof-Off used on a wet area will run right off with no impact.
Tips:
1. The wall usually remains dry even in rain.
2. The railway yard is open M-F till 4 or 5, via the gate at the end of the block. If possible, resupply water and rags during those hours. (Water from the hose at the other end of the trailer; rags from the supply shed.) There is also a water source, though awkward, under a rectangular cover on the ground at the northeast corner of the multicolored little Muni control building which is located at the corner of Duboce and Church.
3. In emergencies, you may use the hooked broom handle (usually missing) to reach the hose through the fence, but that requires some dexterity to turn the brass valve on a quarter turn toward you and then off when you are done.
4. If you look carefully, you'll find that this supply cabinet contains small bottles of two other solvents that have never been tried (nor needed) just in case Goof-Off and Cleverclean don't work.
5. To remove bird shit or spilled soup (this is common as Tuesday there is a soup line here), just use water and the scrub brush.
6. [The late] Dave Pharr [was] the manager of the Market Street Railway Yard (415-552-3055).
7. Joel Pomerantz is the mural coordinator (415-505-8255).
8. The San Francisco Bicycle Coalition (the mural organizers) can be reached at 415-431-BIKE.
A NOTE ON TOXICITY: There is no "away." Harmful chemicals, when washed away, are likely to be hanging out somewhere else continuing to be harmful. If you are removing large amounts of paint, make arrangements so that your residue doesn't flow into the sewers and water supply.
Varnish Dealers
Graffiti Control Services of San Bruno (650) 355-5016 sells two-part, water-based acrylic Graffiti Defenz Sheercoat, that we used. They sprayed it on for us. I don't know whether they make it or buy it from someone else.
Precita Eyes Mural Arts Center in San Francisco 2981 Twenty-fourth Street west of Potrero (415)-285-2287 also sells jars of the Sheercoat, but they are sometimes out of stock and expensive for large murals and won't spray it on for you and can be difficult. They are a convenient place to get the (always expensive) Cleverclean solvent for removing graffiti once you have a varnished mural. You will need to put it in your own spray bottle.
More will be added to this list as I get the chance. (PLEASE let me know if you have any place you'd recommend for this list.)
Resources and References