In discussing the cleaning of the Statue of David in class Thursday, we learned that there are many successful techniques that can be applied. Conservationists can use an anionic exchange resin, solvent gel, white spirit, and…poultice of cellulose? What is poultice of cellulose? I imagined some kind of green jelly spread, while Dr. Norton imagined the soft stone tool a person uses to scrape dead skin off their feet. Courtney, the only person in the group with art conservation experience, did not know the answer either. Nobody had a clear idea of what poultice is, so I was assigned the task of discovering what exactly a poultice is.
There are multiple kinds of poultice. Cataplasm, another name for poultice, is a medicated spread put on cloth over a part of the body that is injured. I didn’t think David was in such pain. The second definition of poultice is a porous, solvent-filled solid used to clean stone- much better.
In class, we discussed how a stone becomes stained with the statue, The Thinker. Stone is a porous substance that becomes stained once a solution goes through the surface and evaporates to leave a solid solute behind the stone layer. Poultice is made from a malleable and porous material, usually paper, whiting, or flour. In our example, the porous material is a cellulose pulp. The sponge type solid is filled with a solvent (alcohol, ammonia, acetone). The poultice and solvent are applied, and the solvent dissolves through the stone pores and equilibrates between the stone and poultice boundary. Once the poultice is removed, so it’s a portion of the dissolved stone solute stain.
Besides cleaning marble or other stones, poultice of cellulose is also used to clean wall paintings and to conserve textiles. It turns out poultice is nothing like what we imagined, but it is an effective cleaning method nonetheless. Now we now that David will never need a dermatologist because his pores remain clean with poultice of cellulose.
References:
Grissom, C.A. “Methyl Cellulose Poultice Cleaning of a Large Marble Sculpture.” VIth International Congress on deterioration and conservation of stone. (1988), pp. 551-562.
Lemiski, Shawna. “An Investigation of Poultice in Materials for Textile Conservation.” Textile Conservation Newsletter. (1998), pp. 1-15.
Luigi Dei, Andreas Ahle, Piero Baglioni, Daniela Dini and Enzo Ferroni. “Green Degradation Products of Azurite in Wall Paintings: Identification and Conservation Treatment.” Studies in Conservation, Vol. 43, No. 2 (1998), pp. 80-88.
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