Page 402 - Copper and Bronze in Art: Corrosion, Colorants, Getty Museum Conservation, By David Scott

1. Incralac
2. Sedonalacq (an ethylene glycol terephthalate)
3. benzotriazole
4. Butcher's bowling-alley-paste wax (carnauba wax; 3 8 natural and synthetic waxes in
mineral spirits, also known as white spirit; and turpentine or a substitute usually made
of hydrocarbons)
5. National Park Service wax mixture (82% Bareco Victory white microcrystalline wax;
15% Bareco 2000 polyethylene wax; and 3% Cosmoloid 80H microcrystalline wax with
3% benzotriazole added)
6. Tatti wax mixture (85% Bareco Victory brown microcrystalline wax; 10% Bareco 2000
polyethylene wax; and 5% Cosmoloid 8OH microcrystalline wax)
7. no coating (controls)

The results of this study showed that the Incralac-coated panels, both spray- and brush-
coated specimens, suffered some degradation during the sixteen weeks of exposure to both envi­
ronments. There were no discernible differences between the wax mixtures with benzotriazole
and those without. After sixteen weeks there was slightly more deterioration of the wax-coated
samples exposed to the simulated acid rain than those exposed outdoors. After twenty-seven
weeks of outdoor exposure, the wax-coated samples showed more corrosion than the samples
coated with the acrylic materials. Many of the acrylics, however, had a tendency to become
detached from the substrate; delamination of the coating from the substrate around edges of the
coupons was a common problem.
In another study, Weil (1975) reported that Incralac gave good protection as a coating for
outdoor bronzes for at least two years; when the Incralac coating was protected with a micro-
crystalline wax finish that was periodically reapplied, it performed well for about three years.
The practical difficulties of maintaining Incralac coatings was highlighted by Erhardt and
coworkers (i984). They examined the ten-year-old Incralac surface on four outdoor gold-plated
bronze statues in Washington, D.C., and discovered it to be cracked and insoluble. Beale, 39
however, notes that two factors in connection with these bronzes were not addressed in this
study: first, chemical residues were left on the surface from the on-site gold electroplating pro­
cess used on the sculptures; second, the inappropriate use of Incralac over a highly reflective
gilded surface contributed to this particular cross-linking of the Incralac polymer. These surface
conditions not only subjected the coating to higher than normal temperatures but also nearly
doubled the dose of uv radiation. The Incralac was removed by softening with paint remover
incorporating methylene dichloride, followed by pressurized water spraying. Compared with
fresh Incralac, the uv absorption of the weathered material was greater, and most of the benzo­
triazole content had been depleted. Benzotriazole is often stated as being added to this polymer

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