Recently our mold shop was contracted to make four reproductions of a large historic column base. The bases were to be made of a low-cost structural material, so we decided to go with concrete.
The base has an impressive 33” diameter, a height of 8″, and an 18.5” diameter hollow center. The sheer size of the piece meant that a concrete casting was going to be a fairly heavy piece. However, the hollow center greatly reduced the overall weight of the base, while at the same time adding a new level of complexity to the fabrication. Each final casting is around 240lbs.
The first challenge was to make a mold of the original piece. The mold was made using our flexible, self-leveling MasterMold 12-8. To make the mold, we first laid a support form down around the prepped original piece, which was offset 2.25” from the perimeter of the column base. After that was set and sealed, we poured the 12-8 into the form and let the material flow throughout the detail of the original base. The result was a perfectly detailed, symmetrical mold of the original piece. The hollow center was simply represented by a symmetrical rigid plug.
Next, the mold and plug were cleaned, prepped, reinforced, and set to receive the concrete. The casting was made of high-strength concrete, which was reinforced by rebar coated with epoxy. The casting was allowed to harden overnight. The following day the mold was removed and a beautiful, exact replica was revealed. Minor holes, which are typical with concrete even after vibrating, were filled in with a slurry mixture. The casting process was repeated three times with the same mold and plug. Many more castings could be made with the same mold, if needed.
The conclusion of this project proves that combining high-tech solutions with some low-tech ones can still produce outstanding results that are hard to match. We look forward to seeing these new column bases in place and painted at our client’s restoration project in Little Rock, Arkansas.