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Inside The Conservator's Art

A behind-the-scenes look at conserving Egyptian artifacts at the Phoebe A. Hearst Museum ofAnthropology

http://conservationblog.hearstmuseum.dreamhosters.com/?p=360

{ 2010 02 15 }

Putting it all back together : cro codile mu m m yconso lidation and repair

Allison dry cleans PAHMA 5-513 with a soft brush and gentle vacuum.

After crocodile mummy PAHMA 5-513 had been documented, studied and carefully cleaned by gentlevacuuming and brushing, treatment of the shattered coating and detached juvenile crocodiles began. Thefirst step in treating the unwrapped crocodile mummy was the selection of conservation materials forconsolidating the black coating and reattaching the loose juvenile crocodiles. Because the black coatingwas soluble in polar organic solvents but not water or petroleum-based solvents, adhesives that can beused with deionized water and petroleum distillates were investigated. After surveying English-languageconservation literature for accounts of similar treatments, I conducted tests with a group of adhesives thatconservators have successfully used on a range of organic substrates including leather, skin, hair and

natural resins. These adhesives included Aquazol (a water-soluble polyoxazoline compound available inthree molecular weights), several water-soluble cellulose ethers (Cellofas, Klucel G, and methyl cellulose),isinglass (a water-soluble collagen-based adhesive made from sturgeon bladders), funori (a traditional

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water-soluble Japanese adhesive derived from seaweed), and Paraloid B-67 (an acrylic resin composed ofan isobutyl methacrylate polymer, soluble in petroleum distillates).

Because so much black embalming resin had detached and was found loose in the storage mount, I wasable to experiment with different concentrations and combinations of the adhesives directly on smallsamples of the coating. I evaluated the adhesives based on working properties (especially penetration, asthe consolidant needed to flow into networks of very fine cracks), join strength, and visual criteria (changesto the appearance of the black coating and crocodile skin). After testing possible consolidants on detachedpieces of coating, I discretely tested selected materials directly on the crocodile mummy itself. In the end,all of the aqueous materials caused darkening and/or tide lines on the crocodile skin, and failed topenetrate as well as B-67 in petroleum benzine (volatile petroleum distillate that performed well in solubil itytests of the coating).

B-67 has some drawbacks, especially its tendency to yellow slightly with age. However, on dark opaquesubstrates like crocodile skin and the black coating, this was deemed to be acceptable in light of itssuperior working and visual properties. B-67 also seemed less likely to compromise future analysis of thecoating or crocodile tissue, as it is synthetic, and has been recommended by British Museum conservatorsas a consolidant for fossilized natural resins based in part on its lack of interference with post-applicationanalysis of the fossilized resin.

Different formulations of B-67 were used to consolidate the shattered coating and to reattach the babycrocodiles. The shattered coating was consolidated with 5% B-67 in benzine, applied with a fine brush.Most areas were given two applications. In order to reduce possible shine on exposed crocodile skin,these surfaces were softly blotted with a cosmetic sponge or brush as the solvent evaporated.

Allison (wearing magnification device and respirator to prevent inhalation of petroleum benzine)consolidates the black coating on 5-513.

The baby crocodiles and wooden sticks were reattached with tacks of bulked and pigmented 20% B-67 inbenzine. Glass microballoons and carbon black dry pigment were added to the adhesive to create a dark-

colored viscous mixture. Figuring out exactlywhere to reattach the loose crocodiles was a slow processthat required careful examination of the mummy group. The placement of the juvenile crocodiles wasdetermined according to their position upon entry to the lab (the wire wound around the mummy seems to

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have kept the babies fairly close to their original locations), impressions in the black coating, drip directionof the coating on juvenile bodies and corresponding surface deposits on the juvenile and adult bodies.

As the shattered coating was stabilized and the babies reattached, the modern wire was removed. In orderto work on the ventral surfaces of the adult crocodile, the entire body was lifted onto several custom-madeblocks of Ethafoam strapped and clamped to the lab table.

5-513 during treatment; elevated on Ethafoam blocks to provide access to ventral surface.

A mirror and flashlight proved very helpful in seeing the underside of the crocodile. Consolidating the blackcoating and reattaching the juvenile crocodiles has made the mummy safer to handle and display, andmade it easier for viewers to appreciate the crocodiles large and small.

Posted by Allison on Monday, February 15, 2010, at 6:34 pm. Filed under Conservation treatments,Mummies and mummification. Tagged B-67, Consolidation, Crocodile mummy. Follow any responses tothis post with its comments RSS feed. You can post a comment or trackback from your blog.