Sealing the Mould's Outer Seams and the Final Clay Layers
Dovetail grooves filled with plaster, ox-hair and hemp facings, and cutting the mould into propped sections
Continuing the Sforza-horse casting instructions, Leonardo addresses the outer surface of the piece-mould. He proposes cutting a dovetailed groove three fingers deep along each outer seam, filling it with fresh plaster and closing it with sheet iron so the bronze cannot dislodge the seal, then specifies the last clay layers of ox hair, hemp and glue laid crosswise. A final note explains how to cut the mould into propped-up sections marked in advance with projecting nails so it will not stick to the ash-coated model. A small hatched vertical bar is drawn uncaptioned in the upper-right margin.
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Sealing the outer seams with a dovetail groove
So the entering bronze cannot dislodge the plaster sealing the mould from outside, cut a dovetailed hollow three fingers deep and wide along the outer side of each seam. Fill it with fresh plaster, then close it off from outside with an iron plate.
The last clay layers of the mould
Make the outer third or fourth of the mould first with earth mixed with ox hair; at the very last, use ox hair, hemp and earth with a little glue. To every layer of earth give a layer of hemp, now lengthwise and now crosswise, then apply the plates and other irons.
Cutting the mould so it releases the model
Build the mould up to the full thickness that runs from the irons inward. Before inserting the irons, cut it into as many pieces as needed and prop the parts liable to fall; but before beginning, mark the run of the cuts with nails, leaving them projecting as far as the mould is meant to be thick where it will be cut.
Small marginal bar sketch
A short vertical hatched bar is drawn in the upper-right margin without any transcribed caption. It appears to be a small diagram related to the mould's construction.