Inspection
Before the ceramic shell technician begins a piece in slurry, the technician will inspect the piece. This is to ensure that everything is attached, sprued, and vented properly. It is also necessary for the technician to make a mental note of any potential problem areas for the shelling and casting processes.

The First Dip
Once the shell technician has inspected the waxes, they can be started in shell. The first step in shell is to dip them in the primary slurry tank, brush the piece, dip it in slurry again, and coat it with zircon sand. The initial dip coats the piece with slurry and basically gives the technician some slurry to brush around on the piece. Brushing over the slurry-coated piece helps to work the slurry into all of the details of the piece to ensure that they are all captured. It is dipped again before going to the sand to replace slurry that is brushed off of the piece and to even out the coat. The sand is then applied to the piece to give that layer of shell a tooth for the next layer of shell to stick to. The sand used on the first dip is very fine to help fit into and capture the details of the piece. The piece is then returned to the drying rack where it must then dry before a second dip can be applied.

The Second Dip
Once the first dip has dried, the second may be applied. The second dip begins with dipping the piece in colloidal briefly, allowing the piece to drain, dipping it in the primary tank, and coating it with zircon sand. The colloidal dip helps the separate layers of shell bond to one another. The slurry is not brushed in on the second coat since the details have already been captured by the first dip. The sand is the same fine sand used on the first dip. The piece is then returned to the drying rack where it must dry before a third dip can be applied.

The Third Dip
Once the second dip has dried, the third may be applied. The third dip begins with a colloid dip, followed by a slurry dip just as the second dip above. The fused silica sand on the third dip is coarser, approximately the consistency of table salt. Referred to as B sand, this sand is used to start building thickness and strength to the shell, while still capturing a medium level of detail. After it has been coated with sand, the piece is returned, once again, to the drying rack where it must dry before a fourth dip can be applied. (Are you noticing a pattern yet?)

The Fourth and Fifth Dips
The pieces must again dry before additional coats may be added. The fourth and fifth dips consist of dipping the piece in the secondary slurry (also known as backup slurry) and then coating it in B sand. Dips done with the secondary slurry do not need to be pre-dipped in colloidal. After coating the piece with sand, it is returned to the drying rack.

The Sixth and Further Dips
The pieces must of course dry again before each dip. Starting with the sixth dip, the sand is switched to calcined fire clay grog.   Grog is about the consistency of cat litter. Otherwise the dip is the same as dips four and five. The number of dips on a piece depends on the height, the shape, and the overall size of the piece. The larger the piece, the more dips it gets. Most pieces get a total of nine dips, including the sealer coat. Other pieces may get eleven or twelve.

The Sealer Dip
The sealer dip is the last dip put on a piece, and is not accompanied by any sand. Its sole function is to hold down the last layer of sand. Once the sealer dip dries, the piece is ready to be dewaxed and poured in bronze.
 
 

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