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Mammuthus colombi, Colombian Mammoth sculpture Date: Mid-late 20th century
Artist: Charles R. Knight/USA Materials: painted fiberglass cast Dimensions (HxWxD, inches): 29 3/8 x 12 1/2 x 40 3/16 Institution/Owner: American Museum of Natural History Research Library Key Treatment Steps
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Summary
This fiberglass cast of a miniature Columbian Mammoth model was damaged while on display at the American Museum of Natural History. The proper right tusk was broken, and the surface was slightly dusty overall. Solubility testing of the paint layers indicated that the painted surface layer was very soluble in a range of polar solvents, requiring careful consideration in choosing an appropriate adhesive to use for the pinning and adhesive bond system used to repair the tusk.
An initial attempt to repair the tusk using a carbon fiber rod and B72 in xylenes failed. The failure was related to the slow evaporation rate of the solvent, further retarded by the non-porous nature of the fiberglass. The repair was reverse and new methods were considered. Ultimately, B72 in acetone was selected, but a protective coating needed to be applied to the painted surface surrounding the break, in order to avoid solubilizing paint layers. A non-polar, reversible barrier layer of 20% B-67 in naphtha was applied to the surface surrounding the break edges, allowing for the use of B-72 in acetone.
Bulked B72 in microballoons was used to fill surrounding losses associated with the break. The B-67 barrier layer was reversed, and fills were painted to match surrounding areas using Golden Mineral spirit-based acrylic (MSA) resins, which can be removed using non-polar solvents if necessary without damaging surrounding paint layers. The report prepared includes detailed instructions on how to reverse the repairs made, if it is ever necessary for a future conservator to do so.
This fiberglass cast of a miniature Columbian Mammoth model was damaged while on display at the American Museum of Natural History. The proper right tusk was broken, and the surface was slightly dusty overall. Solubility testing of the paint layers indicated that the painted surface layer was very soluble in a range of polar solvents, requiring careful consideration in choosing an appropriate adhesive to use for the pinning and adhesive bond system used to repair the tusk.
An initial attempt to repair the tusk using a carbon fiber rod and B72 in xylenes failed. The failure was related to the slow evaporation rate of the solvent, further retarded by the non-porous nature of the fiberglass. The repair was reverse and new methods were considered. Ultimately, B72 in acetone was selected, but a protective coating needed to be applied to the painted surface surrounding the break, in order to avoid solubilizing paint layers. A non-polar, reversible barrier layer of 20% B-67 in naphtha was applied to the surface surrounding the break edges, allowing for the use of B-72 in acetone.
Bulked B72 in microballoons was used to fill surrounding losses associated with the break. The B-67 barrier layer was reversed, and fills were painted to match surrounding areas using Golden Mineral spirit-based acrylic (MSA) resins, which can be removed using non-polar solvents if necessary without damaging surrounding paint layers. The report prepared includes detailed instructions on how to reverse the repairs made, if it is ever necessary for a future conservator to do so.
Treatment Images
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