PRO Team Field Notes: Stone Benders

By Ashley Shares, Preservation Manager

Headstone before the PRO Team’s work.

When you think of stone, what words come to mind? Strong? Solid? Inflexible? Well, a walk through Oakland Cemetery will show you that these adjectives aren’t always true of headstones. Thin, upright marble tombstones are especially fragile. They are prone to breaking, whether it be from a fallen tree branch, being knocked over by vandalism, or the slow effects of gravity. Sometimes, however, instead of cracking, marble does something incredible: it bends.

Yes, believe it or not, if exposed to the right conditions over a very long period of time, marble can slowly bow. This usually occurs when the stone is in a horizontal position. Examples include a tombstone that has fallen, or a box tomb with a marble ledger stone. In the case of a tombstone, if the ground beneath it is not level, gravity will exert more force on less supported areas, pushing them down, while supported areas will remain in one position. This usually breaks the stone eventually, but in rare instances like one stone the PRO Team just worked on, it bends it instead.

John Butler died in 1882 and is buried in Lot 1, Block 302 in the East Hill area at Oakland. His is not the only burial on the lot, but it is the only one marked. The restoration of Block 302 is part of the PRO Team’s critical restoration efforts this year, due to its extremely deteriorated overall conditions which include entirely tumbled-down walls as well as Butler’s bowed headstone.

In order to re-set the tombstone, it had to be stabilized. When a piece of marble bends in this way, the stone loses its strength in the curved area. If the stone were to stand upright, gravity would put press heavily on the curve, possibly causing a break. Leaving the stone horizontal and building a concrete pad for it to rest on was another option we explored. We ultimately abandoned this option because it would allow water accumulation on the headstone’s face, causing more rapid deterioration of the already-faded carvings. Since an upright position was the best bet for saving stone’s historic elements, what we needed to do was prevent pressure from building on the high point of the curve once the stone was back up.

Lightweight bracing on the headstone.

What we did was design a lightweight brace of stainless steel and aluminum that hugs the monument tightly on the sides, both above and below the high point of the curve. Padding supports the curves and prevents the steel from damaging the monument. First, we dug a nearly 3 foot hole and embedded a hollow squared aluminum pole in a concrete anchor. This part acts as the brace’s “spine”. When the concrete was dry, the pieces of the brace were attached to the frame (“ribs”).  The headstone was carefully lowered into the hole directly in front of the spine and the pieces of the brackets were clamped on the sides above and below the curve. All bolts were tightened and we backfilled the hole with soil. Every few years, the foam will need to be replaced but the brace should last many decades because all materials used are non-rusting.