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Rubber Molds Made for Columbia University Post Tops

Rubber Molds Made for Columbia University Post Tops

New Haven, CT – Grand Light was contracted by Columbia University to reproduce lighting components on existing lamp posts throughout the Morningside campus. Grand Light will cast bronze finial components for 15 of the existing lamp posts, which are replicated from an existing that was removed from one of the posts.


Each finial is made up of 5 components: finial base, finial bottom, finial top, finial ball, and an eagle. Grand Light will create a separate mold for the casting of each part. Shown below are three steps in the first process of mold making, there are many steps to each process and each is very time and labor intensive. There will be days of individual steps for each step of the entire process, until pouring day and that day is a one shot deal, you either yield a good casting or start all over. That is why this process is so intensive because each step is critical to yield a good casting.

The molds are cast in rubber and split to pull off the original piece. Then the molds are put back together and filled with wax encapsulating the entire component. The mold then moves to the “slurry room”. An intensive process of dipping and applying slurry (ceramic based mixture) in a temperature and humidly controlled environment will began. This process will take several days to complete as the slurry has to completely cure out and dry before applying the next coat. This process continues until the slurry walls have a consistent thickness and is strong enough to hold together under the pressure of 2300 degree bronze. The slurry form is then supported by applying wax (structural) rods to hold the voids open and support the ceramic shell in every area to keep the mold from collapsing during the pour. Once the rods are in place and the ceramic shell is completely cured out the mold is ready to pour. They will get each piece of this assembly in a cured state of slurry and pour all of them at one time using one heat of the furnace.

 

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