Witch’s Brew

by Gaby Kienitz, Head Conservator

Conservators have all the trappings of a magical enterprise — a stock of arcane ingredients, “potions” that we mix up ourselves, tongue twisting phrases that we use and transformative powers on objects. Don’t believe me? Well, I might not have eye of newt or puppy dog tails, but I sometimes clean an object with my own spit; I’ve used things like fish skin glue and lamb intestine for repairs; and I regularly use an ethyl methacrylate methyl acrylate copolymer.

A cast iron tea pot before (above) and after (below) Gaby works her magic.

In order for the “magic” (a.k.a. work) to happen, a conservation lab needs lots and lots of ingredients and tools. There is such a huge variety of objects that come through the lab with such a range of problems, that a certain treatment might be performed only occasionally and thus only a small amount of a certain supply is needed. Sourcing just a little of these supplies can be a challenge. Imagine my dismay when I was missing a few milliliters of one crucial ingredient for the solution needed to treat a collection of cast iron cookware and fire dogs from Corydon Capitol State Historic Site that had been damaged by water leaking from a chimney. My magic wand was broken!

The ingredient I needed — phosphoric acid — is so common that I couldn’t imagine not finding it sold locally. It’s what gives some colas the “bright” taste, it’s a homeopathic medicine, brewers and hydroponic gardeners use it to lower the pH of their mash and water respectively, it can be used as a flux for soldering metals, and it’s used as a rust and hard water scale remover. Everyone I called either didn’t have it or didn’t have it in the pure form that I needed. It was hard to fathom that I would need to have it shipped from elsewhere, like a rare and precious commodity.

Fire dogs before (above) and after (below) conservation.

Just as I was about to give up, Tuxedo Park Brewers Supply came to the rescue with what I needed. I’m used to buying supplies from some interesting places, but theirs is at the top of my list. Their shop exterior is a brightly painted scene of orange and yellow wheat fields with a bright blue sky that you can only find by going down an otherwise drab, nondescript alley in Fountain Square. Yes, that’s right, their storefront is the alley.

This was a simple potion that I mixed for the treatment of the corroded cast iron, just some tannic acid and phosphoric acid. Tannic acid is a product that has been used since ancient times for making inks, in fabric dyeing and leather processing; it occurs naturally in tree galls, the bark of some trees and in tea leaves. It sounds scary, but it comes in the form of a fluffy, tan colored powder. Luckily, I had a whole bottle of tannic acid powder and once I mixed that with some de-ionized water, added a few drops of the phosphoric acid and heated it up, it was ready to be applied onto the surface with hog hair brushes. Through the magic of chemistry, the rust is converted to a stable, black colored corrosion layer. You can see for yourself what a few ingredients can do to change the appearance of some frightening looking objects. If you want to see them in person, you’ll have to visit Corydon Capitol State Historic Site.

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