Best Protection for Watermedia

Q. Are there any alternatives to glass for protecting my watercolor and other watermedia paintings?

A. This question bridges both technical and aesthetic concerns. The proliferation of watercolor canvas, which provides a clothlike surface that accepts watermedia (watercolor, gouache, casein, acrylic and egg tempera), raises the question of the advisability of applying a surface coating to a finished watermedia work as one would to an oil painting.

From a technical standpoint, understanding the physical structure of watermedia—particularly watercolor—is important. Watercolor is a combination of pigment with a water-based resin, typically gum arabic, that binds the color to the support. Watercolors may also contain agents to make dry pan colors softer, so they dilute quickly with water. Other additives may be used to retard mold growth. The system is fairly simple by comparison to other water-based painting materials.

Watercolor’s chief attribute is the level of transparency that can be achieved by controlling the ratio of paint to water. That factor is one of the most compelling reasons to work in this medium, because so much of the appeal of watercolor is the interplay of the paper substrate and the transparency of the color. The surface of a watercolor displays passages of colored paper saturated with either muted or blazing hues. The underlying soft texture and character of the paper plays an important part in the visual equation. Applying watercolor to a canvaslike material is another substrate worthy of exploration, the canvas imparting a different look and feel from that of watercolor paper.

Applying a surface coating intended to protect the medium so that it can be displayed without glass creates a critical and fundamental change to the appearance of a watercolor painting. With a surface coating, a finished watercolor approaches the visual equivalent of an oil or acrylic painting. Colors take on a wet, saturated look that opposes the original character of watercolor. Further, since the ratio of gum arabic to pigment is low and vulnerable to infiltration by other media, the application of an acrylic surface coating essentially transforms the watercolor into an acrylic painting.

Glass or plastic glazing (clear, acrylic sheet, similar in appearance to glass) provide the best protection for the fragile medium of watercolor. Plastic glazing treated with ultraviolet inhibitors not only helps preserve the colors in a work of art, but it also protects paper that’s vulnerable to ultraviolet damage, which would cause the paper to discolor as it ages. Much of the objection to the use of glass or plastic glazing is the glare it generates, but creative lighting and strategic placement of hanging artwork subdue this annoying problem. Considering the potential harm that light, physical contact and environmental pollution can cause, glazing not only provides the best protection for watermedia, but it also avoids compromising the appearance of the finished work of art.

Note: This article first appeared in the November 2008 issue of The Artist’s Magazine, available at

Michael Skalka has degrees in art history and museum studies. He is chair of the subcommittee on artist’s material for ASTM International.



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