March 2025 marked the completion of a commission for Neumann Brothers Inc. sidewalk plaques. These plaques were designed, patterned, sand molded, cast in bronze and finished at Max-cast. Measuring 3×6″ and about 3/4″ thick, they were designed to be set into sidewalks and other project areas the Neumann company completed work at. The patterns were made first from a photopolymer plate made with a Hercules Merigraph machine. They were then made into a double pattern box, with a latched flask and bottom board. (see photo) 5 pattern boxes were made containing 2 photopolymer plates each so that 10 plaques could be sandmolded at a time. The sand molds were then lined up and clamped together in strings of 5-20 patterns in a method called the H method. “H” stands for horizontal, as with this method the sand molds are lined up horizontally and poured so that they each fill with an equal amount of bronze and turbulence is greatly reduced which improves successful castings. Unfortunately it is common for castings to fail and for there to be too many defects to use the piece so the process must be repeated over and over again, making new sandmolds each time. In this case, it turned out to be a number of the photopolymer plates were not uniform and otherwise defective. To correct the problem with the pattern, a rubber mold was made of one of the completed plaques and the pattern was redesigned with the rubber pattern in place of the photopolymer plate. This worked out well for sandmolding the remaining plaques that needed to be completed to fill the order of 80 sidewalk plaques. Once the plaques were finished and the back bolts were welded on they were painted and the face was sanded down perfectly to make for a flawless plaque.
H-method for sandcasting used for Neumann Brothers Inc. 3×6″ bronze sidewalk plaques