This week I applied the isolation coat and the final varnish. I allowed the paint layer to dry a week before commencing on sealing the mural. I have varnished my own work and understand the basics of what that entails. But I have never worked a varnish over a large area. I spoke to Golden Paint colors technical support on 2 separate occasions to get the proper understanding of how to mix and apply the coats. There were many things to consider. I needed clear days without rain, the proper temperature ( not below 49*) , the right proportion of each solution as both had to be thinned in order to apply properly, and method of application.
First I needed to apply the isolation coat. An isolation coat is basically made of the same material as the acrylic paints and it acts as a permanent barrier between the paint layer and the final varnish. This is necessary if for any reason the varnish will have to be removed due to graffiti, excessive wear of the elements etc. This coat protects the paint layer through the process of removal of the final varnish which requires some pretty hot chemicals to get it off.
I used Golden Soft Gel Gloss. It is like an acrylic medium, very thick out of the can. It is necessary to thin this with water in the proportion of 2 parts gel to 1 part water. It can’t be too thick or it will appear cloudy rather than perfectly clear. It also needs to be applied by brush in a very small area at a time. I worked in an area that had the natural division of the concrete blocks that were the structure of the wall. These were 2′ X 8’divisions that were marked in the wall. I worked from top to bottom being careful not to excessively brush the area. I did not want any foam or bubbles. I also tried not to get any streaking. Streaking was particularly evident in the dark areas and I needed to take special care brushing it on in those spots.
Another issue that I needed to deal with was all of the pits in the wall (these occur naturally in concrete and are also the areas where the concrete will begin to wear away over time). These pits tended to fill up with the gel gloss and appear white and also run if I was not too careful. I found that after I had applied a section with the gloss, I had to go back and re-check and touch up around the holes. They did dry eventually and appear clear, but it took several hours. I applied the isolation coat in a very methodical way section by section. If any one has ever visited the Catskills this time of year, one knows that the weather is particularly transitory. Even as I was working, on supposedly a clear day, the clouds threatened. Thankfully, I was spared any rain during the process. I found that after about 3 hours in 65*, the isolation coat dried, even in the pits. It took 4.5 hours to apply over the 51′.
The next day, I applied the MSA Varnish by Golden. This was also difficult to apply. This too, had to be thinned. The proportion was 3 parts MSA to 1 part thinner (Golden) or Gum Turpentine. It was very toxic and strong-smelling. I wore a respirator, hat and long sleeves as I did not want to get anything on me or breath in the fumes. The consistency of the solution was that of “maple syrup”. When I first mixed the solution, I applied some to see if I could spread it. At first it was too thick. I added another cup of thinner to the solution and that gave , what I considered the right flow. This coat had to be applied similarly to the isolation coat. I worked in small sections, applying it by brush. The solution was very clear and was difficult to see over the isolation coat. I had to cock my head to the side to see it on the wall. This also had to be applied very, very thinly.
This coat tacked up much faster that the previous coat. I, therefore, had a difficult time with the pits in the wall. I have to say, I did my best to make sure there was some contact between the varnish and the holes. But I also was careful not to over-brush the varnish(which causes cloudiness and streaking) as this was paramount to an even look. I was not going to sacrifice the clarity of the over-all effect by hitting every pit on the wall. This coat dried in about an hour to the touch in 65* temperature. The next day the surface was hard, although it takes about 2 weeks for the coat cure completely.
The one thing that astonished me was the final look of the mural. Even though I had sealed the wall completely before applying the paint, there must have been a slight dullness to the wall. When I varnished it with the last 2 coats, the wall image became more distinct. It was a very subtle thing, that possibly others might not have noticed. It could possibly be that the varnish itself added a gloss that was not there originally and added to a sharper look. Over-all I am satisfied with the final look.
The images below show the mural in it’s final state panning left to right.
Congratulations to you and your students on the mural!