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Studio Craft: Using Resin over Paint

Ask the Expert: I'm trying to layer 2-part epoxy-type resins over my paintings because I want a deeper glaze than I can obtain from mediums alone. I want to apply adeep layer, but the resin spills over. Some of my paintings are in oil and some are in acrylic. Can you give any tips for this technique?

A: Use of casting resins with paint should be treated as an experimental technique. Any time the artist considers using an untested combination of materials, we think it's a good idea to investigate whether the visual/pictorial objective can be accomplished with something known to produce durable results. In the case of catalytic resins, possible alternatives might include acrylic mediums formulated for poured techniques or thick, clear applications.

Of course, not every artist necessarily wants predictable results, or wants to deal with the long drying times associated with water-based mediums. Catalytic resins adhere to most surfaces and set quickly to a tough, water-clear solid, so painters often experiment with incorporating resins into mixed-media pieces.

There are a few factors to consider before applying catalytic resin over a painting. Artists' oil and acrylic colors are not tested for interaction with catalytic resins, and while we're not aware of any specific problems, it might be possible that some pigments could interfere with hardening and curing, or react in another, unpredictable way. Also, if a haze develops between paint and resin, there's no way to remove the resin for cleaning. 2-part resins sold as art supplies are generally polyester orurethane compounds, which may develop a yellowish cast over time.That said, many resins are recommended for use over painted surfaces, and we're not aware of any reason why they shouldn't work well over a completely cured artistic painting.

There are some safety measures that are necessary when using this type of material. Above all else, of course, read and follow all package instructions. Resin hardeners are very harmful when they come in contact with eyes, so goggles or face shield may be necessary. Nitrile gloves are usually recommended. Some resin kitinstructions recommend "torching" (light application of flame) to chase off bubbles, but that is probably not advisable when working with a painting.

As with any new, "off-label" combination of materials, it's important to test a small amount before covering an entire work of art, just in case the result is not as expected. We think a cured (2+ week old), dry acrylic painting is probably the best choice for this approach, since oil paint continues to dry chemically for a long time, but if the oil painting has been dry for a year or more and has received a coat of picture varnish, it might work as well.

The type of resin used will determine how thickly it can be applied. Catalytic resins produce heat when they cure, and each has an optimal temperature where hardening is best achieved. Casting resins are formulated to set in a mass, rather than in a skin or thin layer, so this type of material may not set up properly in a poured layer where heat is rapidly lost. If painted in a thin layer, casting resin might stay sticky permanently.

Poured, or "laminating" resin is designed to run over the edges of the substrate, but if that is not acceptable for your objectives, it might be possible to hold it in place while the layer sets up. Sulphur-free plastilina could be used to create a "dam" all around the edges. It has to be sulphur-free because the standard type can interfere with resin hardening. The clay might stain the edges of the canvas if left unprotected, but a layer of painter's tape might help reduce this. Poured resins can build up a lot of heat if applied too thickly, so it's important to follow package guidelines for film thickness.

Because of the weight of a thick resin application, rigid panel supports are probably better suited to this approach. If you do plan to attempt pouring resin on a stretched canvas, it should be supported from behind to prevent sagging and pooling.

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