How We Made a 30CM Lady Justice Silicone Mold

This project shows the real workshop process for making a 30 cm Lady Justice silicone mold with a rigid support shell, followed by a plaster casting test. The sequence is based on this specific workshop run: a small first pour, a second pour about 40 minutes later, about 4 hours of curing, silicone demolding and trimming, plaster pouring, plaster demolding, sanding, and final inspection.

The recorded times describe this project only. Follow the instructions supplied with your own silicone and casting material.

Materials: Lady Justice master used for this G6003 workshop run; silicone used to form the flexible inner mold; rigid sectional support shell; double-sided tape; binder clips; plaster for the casting test.

Tools: mixing and pouring containers; trimming tool; basic assembly tools shown in the workshop video.

Seat the Lady Justice master inside the rigid support shell. Seal the bottom edge with double-sided tape and clamp the shell sections together. Mix a small first batch of silicone and pour only a shallow amount. Keeping the first pour small reduces pressure on the bottom seal and lets you check for leakage before continuing.

After about 40 minutes in this workshop run, check that the first layer and bottom seal are holding. Pour the remaining silicone slowly to fill the mold to its planned level. This 40-minute interval records what happened in this build; it is not a universal timing rule.

Leave the assembled mold undisturbed. In this recorded run, the silicone was ready for the next operation after about 4 hours. Before opening the shell, confirm that the silicone is fully cured and no longer tacky. Use the cure schedule for the silicone system you are working with.

Remove the binder clips and separate the rigid shell sections. Ease the cured silicone mold away from the Lady Justice master a little at a time, supporting thin or detailed areas as they release. Inspect the mold surface before moving on.

Trim away the thin flash and excess silicone around the opening and edges. Work gradually so you do not cut into the detail surface. A clean opening helps the silicone liner sit correctly when it is returned to the rigid support shell.

Place the trimmed silicone liner back inside the rigid support shell and clamp the sections securely. Mix the plaster according to its own instructions, then pour it steadily into the mold. Add it in a controlled stream so the material can reach the sculpted details.

Wait until the plaster is firm enough to handle. Remove the clips and open the rigid support shell, then peel the flexible silicone away from the plaster casting. Release detailed areas slowly rather than pulling the mold off in one movement.

After the casting has dried enough for finishing, remove small seam marks and rough edges with fine sandpaper. Support projecting details while sanding and check the surface frequently so the sculpted features stay crisp.

Brush away the sanding dust and inspect the finished Lady Justice casting from every side. Check the face, hair, shoulders, base, and other detailed areas for clean reproduction. The completed piece from this workshop run measures approximately 30 × 20.3 × 19.7 cm.

A longer workshop record of this build is available at https://www.bksilicone.com/how-30cm-lady-justice-silicone-mold-uses-support-shell-g6003/