Atmospheric humidity is very high in the deep south especially during the summer. Humidity ranges between fifty and one hundred percent and a heat index of 115 fahrenheit is not uncommon. The summer air is so muggy, it has the texture of hot broth.
The Stained Glassworks and David Field’s Carpentry has been commissioned by a church in Maben, Mississippi to clean and repair its stained glass windows. According to Jane, the interior sides of the windows have a few breaks and are covered in organic growth like mold, mildew, or algae. Representatives of the church claim the air conditioner doesn’t run during the week to save money.
In the process of cooling down the interior of a building, an air conditioning unit reduces extraneous humidity. Water vapor condenses on the cold refrigerating coils and drips from drain tubes and ports on ac units. It’s been as hot as usual this summer and without a running air conditioner, all that mold or mildew would need in an interior is a little shade from trees or even just the overhangs.
This month marks my second year with Jane at the Glassworks. I’m headed to the studio today, Monday, August 15, to load the van with our supplies and make sure we have everything we need. The windows are high and will require scaffolding which, by itself, I am familiar with but in the past two years, I’ve only learned about the construction of windows. I am inexperienced in the professional cleaning or restoration of stained glass.
The website buildingconservation.com has a great article on cleaning stained glass windows and it brought me up to speed. Dirty but strong glass can be cleaned with cotton or wool and distilled or deionized water. Preferably, raw cotton wrapped around a chopstick or skewer is dipped in deionized water and rolled across the surface of the glass. Rolling, not rubbing, the cotton swab across the glass to pick up and remove the mold and dirt doesn’t disturb paint or the rest of the window. Rust deposits could be cleaned with plastic bristle brushes or pot scrubbers but only as a last resort.
The article insisted on the delicate care of glass with fragile paint. Over-cleaning glass with fragile paint can result in a catastrophic loss of detail of the glass and very expensive and difficult to repair. The website recommended leaving medieval era and unstable glass for the experts. Deposits of corrosion should also be left to experts and if they are cleaned then the damage they have caused can’t be repaired.
The article includes a case study of the restoration of the windows in St. Mary’s in Stowting, Kent. It involved the removal of invasive plants, microbes, and other contaminants.
“The three small windows in St Mary’s Church were so densely covered with dirt and microbial growth that no-one had given them a second glance in decades. Ivy had invaded the space between the rusting safety grilles, covering the stained glass even further. The church is situated in a deep and damp valley, and is surrounded by trees that grow very close to the building. This created a sheltered and stagnant micro-climate with very high humidity and low light levels. All of the church’s windows therefore showed dense micro-organism growth on the inside of the glass.”
Microbial growth was stopped with a mist of water and ethanol. Loose paint was stabilized with epoxy resin that was applied whether the organic material could be removed or not. Finishing the restoration included new glazing and drainage equipment to remove excess humidity from the window’s exterior.
“The protective glazing was installed into the original glazing groove and sealed in. A condensation tray was installed at the bottom of the outer glazing, with a drainage pipe that would evacuate run-off to the exterior.”
Jane had already chosen to rely on several of the techniques from the online article, picking up distilled water and towels. According to her it should take a couple of days at the most and I am pretty excited about the new challenge. Pictures and more are sure to follow.
Mark N Huerkamp 