Making Perfect Casts From Molds

Mold making is deeply entwined with casting. In fact, it is impossible to make a cast without making a negative impression of the model in the form of a mold. Learning both the arts becomes essential.

The casting process always begins with how to make a mold. The artist can choose the mold making material and the technique depending on the nature of the model, the preferred casting material, personal dexterity and so on. While the mold can be made using clay, wax, plaster, resin or rubber, the method can vary from simple block molds to more complicated blanket molds using the brushed, poured or glove mold making system.

Here, the artist also has to decide whether they will be making a mold in its entirety at one go or in parts. The latter is quite an intricate and time-consuming process. But it becomes essential if the model has deep indentations, protrusions or undercuts. This calls for making keys and sprue holes in the parts of the mold as well.

Once the mold parts are ready, the artist can move to the casting process. First timers often wonder if the cast will also be made in parts and need to be fused together later.

This is not actually the case in reality. In fact, making a cast in multi-part molds is similar to casting in a single piece mold save for a few extra steps.

The casting process

The mold parts are thoroughly cleaned and dried before coating with a release agent. Then the parts will be lined up using the keys so that they align properly. Mold straps or heavy duty rubber bands are needed to bind the mold parts together and keep the casting material from leaking out. In case the mold is flexible, backing boards are placed on either end of the mold to keep the mold from bending or collapsing on itself. The bands go over the boards and hold the entire arrangement in place.

Now all that is required is pouring the casting material into the mold through the sprues. This should be done slowly to avoid air bubbles. The mold is tapped a few times to allow the plaster, rubber or resin to fill the indentations and settle everywhere properly. It is advisable to continue pouring till a bit of the material starts flowing out from the holes.

The mold should be allowed to sit for a couple of hours or even overnight to ensure proper curing. Once set, the bands can be removed and the mold parts separated with a gentle hand. This will reveal the cast in its entirety!

The cast is then removed and finished with sandpaper and paints as needed.

Therefore, newbies need to know how to make molds and casts of different types before attempting any project. Perfection comes with practice and they can learn the tricks through trial and error. Very soon they will also be able to create flawless casts from impeccable molds.

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