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Conservation Notes: Resurfacing Large Two Forms

July 30th, 2015

By Lisa Ellis, Conservator, Sculpture and Decorative Arts

Standing at the corner of McCaul and Dundas streets since 1974, Henry Moore’s monumental sculpture Large Two Forms has become an important part of Toronto’s cultural landscape. Scores of school children, families, local residents and out-of-town visitors enjoy sitting in the large void of the northern element, exploring and enjoying the surfaces and forms and now, perhaps more than ever, posing for photographs and selfies with the bronze giant.

Recently, the sculpture has begun to show its age. Those resting in the forms’ voids have inadvertently polished away the original textured surfaces. Pollution and moisture from the air have reacted with what was once a golden-brown surface, most notably on the top of the forms, turning it into a powdery light green corrosion layer. Worrisome stress cracks had opened up across welded joins and in the larger void where many visitors sat or stood for photos.

With generous funding and support from the Henry Moore Foundation, and after much planning and preparation, a small team of AGO staff members spent a month in the summer of 2015 addressing these issues.The treatment plan consisted of repairing stress cracks and attending to the appearance of the sculpture.

Repairs
Stress cracks caused by different rates of contraction and expansion between welded areas and cast areas of bronze — as well as forces imposed by people sitting, standing and jumping on the surface — had to be addressed first. Brian Renne, a welder from Phil Bouchard & Sons in Scarborough, Ont., started the repairs by first drilling small holes at the ends of the stress cracks to prevent their propagation during the subsequent treatment steps. The embrittled bronze around the cracks was then removed with an electric grinder. A TIG welder was then used to fill the voids with molten silicon bronze. Once the fill material had cooled, a grinder was again used to smooth the newly added metal. In some areas, new welds or repairs were integrated into the surface of the sculpture by replicating the texture of the surrounding material with a grinder.

Repatination
James Copper, conservator at the Henry Moore Foundation, has extensive experience in the patination of Moore’s bronzes, including that of other versions of Large Two Forms, one of which is in the Foundation’s collection. When it was first installed in Toronto, the AGO’s cast of Large Two Forms had a golden-brown patina from the Noack Foundry in Berlin. However, over time the sculpture’s original patina had changed. Visitors’ interactions with the sculpture’s northern element — the one with the larger void — had not only removed the original patina but also polished away the surface of the metal. The deep grooves and hatching marks with which Moore had intended to cover the entire surface are no longer present in this area. As well, moisture in the air coupled with pollutants caused the golden-brown colour of the sculpture to turn light green over time: this was most noticeable on the tops of both forms. In addition to these changes, the newly added silicon bronze used to repair stress cracks was very bright in colour and needed to be reintegrated tonally with surrounding areas.

The effort to improve the sculpture’s colour began by lightly abrading the surface to remove powdery corrosion, especially evident on the tops of the two elements, as well as previously applied wax coatings and lacquers. Traditional patina formulas were applied in layers — these solutions have been used for hundreds of years by metal workers to change bright yellow brasses and bronzes into rich browns and a range of greens and blues. Copper used a number of techniques: sponging and dripping the liquid formulations over the surface in places that would emphasize the organic shapes of Moore’s sculpture as well as natural weathering patterns. Three weeks were devoted to this process, and even the weather cooperated: rainwater washed down the bronze’s surface in between applications of the chemicals. The sculpture’s height and forms posed quite a challenge to the team: they had to use ladders to reach the uppermost areas, which demanded the same amount of attention as easier-to-reach areas.

Protective Wax Coating
When the sculpture was successfully toned with its new patina, a protective microcrystalline wax coating was applied. The metal surface was heated with propane torches, driving off any water bound to the surface or trapped in highly textured areas. A custom mixture of microcrystalline waxes was then applied to the hot surface using brushes. The residual heat melted the wax, allowing it to flow into small crevices and features in the uneven surface and also allowing the wax to melt into a uniform and cohesive layer.

Thanks to everyone who worked on this restoration and to everyone who supported, expressed interest and spread the word about it!


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