Direct Sand Molding for Architectural Castings

Directly molding sand castings from historic original castings or other physical models relies upon the skills of an experienced mold maker to create a sand mold for metal casting without a foundry pattern by using an original casting or model as a loose pattern. A typical foundry pattern is constructed to take advantages of industrial process efficiencies of scale and castings are made less expensive by increasing the volume, but loose pattern molding is economical for a handful of castings or even reproduction of just one casting. There are some setup costs for making a directly molded casting, but most of the work goes directly towards making the sand mold.

Hard tooling or a foundry pattern is sometimes necessary to achieve dimensional precision and repeatability, but a directly molded sand casting can capture some original textures and details better than hard tooling. Rough, distressed, or intricately detailed designs tend to work well in directly molded sand castings.  Whereas castings with geometrically precise or smooth surfaces tend to mold better with hard tooling. Richmond Iron chooses the best molding method for each project based on the volume, shape, size and metal to be poured.

Direct sand molding from original castings for historic reproductions.

Historic cast iron can be reproduced by directly sand molding an original casting. Reproductions are 1% smaller than the original, but they are otherwise exact reproductions of the original and even the smallest details are captured and reproduced. Direct molding small numbers of casings avoids the costs of a foundry pattern.

Direct Molding Cast Iron, Step by Step

Original cast iron panel rigged to follow board for loose piece molding.

Step 1

Prepare follow board for original casting to be used as loose pattern.

Filling cope half of mold with resin bonded sand.

Step 2

Fill mold halves with resin bonded sand.

Opening mold to remove loose piece pattern.

Step 3

Open mold to remove loose pattern (original casting).

Drawing loose piece pattern from drag.

Step 4

Remove loose pattern (original casting) from mold.

Drag half of mold with loose pattern removed.

Step 5

Clean and inspect mold after pattern is removed.

Closed mold ready for pouring.

Step 6

Close up sand mold and pour with molten metal.

Direct Molding for Accurate Reproduction of Details

Directly molding in sand captures the finest details of original castings. Reproductions are nearly indistinguishable from originals including surface aging from rust or wear. Sand castings directly molded from originals will be one percent smaller than the original due to thermal contraction and may have some additional sand texture not found in smooth originals, but otherwise, direct molding is the most accurate way to reproduce sand castings from historic originals.

Comparison Gallery of Historic Original Castings versus Reproductions by Direct Molding in Sand

Direct Sand Molding for Art Castings

Found objects, botanicals and fabrics create amazing castings when directly molded in sand. Sand castings are unexpectedly good at capturing the texture of textiles and botanicals. Unlike a ceramic shell or lost wax casting, sand molds will impart some sand texture to the casting, but the sand texture does not obscure the visual impression of fibrous details. Our brains are exceptionally good at finding patterns of fine lines amongst random grains of sand, and by directly molding in one step, the fuzzy textures of textiles are captured and transformed by casting into metal.