Treating the Screw-piles

Conservator Cait Shaffer has begun cleaning the much concreted surfaces of the two screw-piles from the Drum Point Lighthouse that recently arrived at the MAC Lab. She initially tried cleaning the artifacts with air abrasion and a Dremel rotary tool, but many of the concretions on the objects are too hard for these methods to remove them. Cait is now using an air scribe, which is like a tiny jack hammer, and it has been working well. And for the thickest of the concretions, she is dexterously using a chisel and hammer for their removal. After the cleaning process is completed, a protective coating will be applied to the screw-piles.

Using the air scribe to remove concretions

Heavily concreted screw-pile

Close up of concretion

Screw-piles in Conservation

Two screw-piles from the Drum Point Lighthouse have just arrived at the MAC Lab for conservation treatment. Screw-pile lighthouses were built on pilings that have been screwed into soft river or sea beds (the “screw-pile” is the piling itself with an auger, or drill bit, attached to the end). This type of construction allowed specifically for the yielding bed of the Chesapeake Bay, and screw-pile lighthouses became widespread in the Chesapeake region. Construction of the Drum Point Lighthouse began in 1883 and workers finished screwing the pilings into place in less than three days – the entire structure was completed in less than 19 days! The lighthouse was decommissioned in 1962 and it was moved from Drum Point, at the mouth of the Patuxent River, to the Calvert Marine Museum in 1975 where the admission fee for the museum includes a tour of the lighthouse. Drum Point Lighthouse is one of only three surviving Chesapeake Bay screw-pile lighthouses.

Conservators use the crane to bring the auger portion of
one of the screw-piles into the MAC Lab.

Drum Point Lighthouse in 1915.