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Putting it all back together: crocodile mummy consolidation 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 gentle vacuuming and brushing, treatment of the shattered coating and detached juvenile crocodiles began. The first step in treating the unwrapped crocodile mummy was the selection of conservation materials for consolidating the black coating and reattaching the loose juvenile crocodiles. Because the black coating was soluble in polar organic solvents but not water or petroleum-based solvents, adhesives that can be used with deionized water and petroleum distillates were investigated. After surveying English-language conservation literature for accounts of similar treatments, I conducted tests with a group of adhesives that conservators 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 in three 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 water-soluble Japanese adhesive derived from seaweed), and Paraloid B-67 (an acrylic resin composed of an isobutyl methacrylate polymer, soluble in petroleum distillates).

Because so much black embalming “resin” had detached and was found loose in the storage mount, I was able to experiment with different concentrations and combinations of the adhesives directly on small samples of the coating. I evaluated the adhesives based on working properties (especially penetration, as the consolidant needed to flow into networks of very fine cracks), join strength, and visual criteria (changes to the appearance of the black coating and crocodile skin). After testing possible consolidants on detached pieces 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 to penetrate as well as B-67 in petroleum benzine (volatile petroleum distillate that performed well in solubility tests of the coating).

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

Different formulations of B-67 were used to consolidate the shattered coating and to reattach the baby crocodiles. 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 in benzine. Glass microballoons and carbon black dry pigment were added to the adhesive to create a dark-colored viscous mixture. Figuring out exactly where to reattach the loose crocodiles was a slow process that required careful examination of the mummy group. The placement of the juvenile crocodiles was determined according to their position upon entry to the lab (the wire wound around the mummy seems to have kept the babies fairly close to their original locations), impressions in the black coating, drip direction of 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 order to work on the ventral surfaces of the adult crocodile, the entire body was lifted onto several custom-made blocks 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 black coating and reattaching the juvenile crocodiles has made the mummy safer to handle and display, and made it easier for viewers to appreciate the crocodiles large and small.

{ 7 } Comments

  1. Nichole | 02/16/2010 at 10:56 am | Permalink

    That’s a really great post, Allison! I learned a lot.

  2. Vanessa | 02/16/2010 at 4:25 pm | Permalink

    The crocodile skin with the resin, and the condition of the material, really creates a very complex treatment. Thanks for putting together such a detailed post on the process of selecting an appropriate consolidant and adhesive. It will definitely be very helpful to anyone treating something similar when not much conservation literature can be found on the subject.

  3. Siska | 02/17/2010 at 3:41 pm | Permalink

    This is a very interesting post! I was wondering how the belly of the crocodile looks like, is it as dark as the back, and did it need a lot of consolidation? I am looking forward to the next post!

  4. Allison | 02/19/2010 at 1:57 pm | Permalink

    @Siska, Yes the ventral surface is also coated and looks similar to the upper surfaces. In some areas is was fairly intact, while others, especially under the chin and throat, required significant consolidation. If you check out the “Babies on board” post and scroll down to the seventh picture, you can see what the underside near the back legs looks like!

  5. Ozge | 02/19/2010 at 6:31 pm | Permalink

    Thanks for the post Allison. How heavy is the piece by the way?

  6. Rams | 02/21/2010 at 12:19 pm | Permalink

    Fascinating stuff. What a lovely blog:)

  7. Allison | 02/23/2010 at 8:02 pm | Permalink

    @Ozge, It’s 19 lbs including its ethafoam/plex/batting support, so probably about 18, 18.5 lbs. I was surprised at how light it really is 😉

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