I repainted a mural on a stone wall inside a small building in India, using artists' oil colors. Over the years a moisture entry problem developed in the walls, causing small areas of the paint to flake off. The problem was successfully corrected on the exterior of the building, and now the damaged areas of the murals inside need to be repaired and touched up. What paint do you feel would be wise to use, oil or
water-based paints?
First, we would think a consolidating layer is needed before you begin the restoration. This should be something removable and because there is oil paint on the surface, which is not the best choice for murals especially ones exposed to moisture and other environmental changes, you should use the solvent-based (NOT oil based, it's actually acrylic) GOLDEN MSA Varnish Gloss. This layer will protect the original painting in the future if more conservation is required.

Second, you want to isolate the MSA Varnish by applying a coat or two of GOLDEN Polymer Varnish. This removes with ammonia and is waterbased. Third, we suggest using the GOLDEN MSA Conservation Colors. These have the same base resin as the MSA Varnish, and can be later removed if needed. As the layers are developed, conservators will apply a coat of Polymer Varnish, so that if needed, they can be selective about removing the varnish. However, it would be easiest if you can complete all of the inpainting in one layer.

Once the artwork part is complete, apply a coat of the Polymer Varnish (gloss), and then finally several coats of the GOLDEN MSA Varnish. We have gloss, satin and matte, all are intermixable for the exact sheen desired. Over time, these layers of MSA Varnish can be removed without disturbing the underlying paints, and new coats applied.

We suggest testing the procedure before doing the actual job, and document the entire procedure, listing materials, pigments, and order. Keep a copy for yourself, and give copies to the appropriate parties/owners/caretakers.

The Web site has information about the MSA Colors and Varnishes, but not so much on the conservation part. For this, you may need to consult other sources.

I painted an outdoor mural three years ago and applied two coats of GAC 500 and two coats of MSA Varnish. I plan to clean the mural and need to know if I should apply additional coats of MSA varnish after cleaning.
It's tough to say you'll need to apply more coats of varnish until you determine if the current layers are still intact. If after you clean a section and the surface looks like it has deteriorated, such as minor chipping and cracking, or most likely just wearing down because of the environment, then a couple more coats are a good idea. If you clean the surface and it looks really good, then you probably don't need to apply more varnish. If you need to do some retouching, you should remove the varnish in the area first. Another muralist recommends using a chamois cloth instead of our normal recommendation of tee shirt material, because this holds more solvent and doesn't evaporate outside as quickly. Soak the material with mineral spirits, then lay it on the area to remove for about 5 minutes or so, and the varnish should come off. You probably want to mask off below the area a little to avoid the solvent from dripping below and causing a streak.

Once you have removed the varnish allow the solvents to evaporate and begin the retouching. After that dries, apply the isolation coat (for the small areas it's probably easier to brush the Soft Gel Gloss thinned 2:1 with water instead of spraying).

Then revarnish and you're done. If you notice colors fading, which should not have happened to lightfast colors in 3 years, you should consider a heavier application of the color to reduce noticeable fading.