Custom Silicone Molds for Sculptures and Figurines

A figurine mold has to protect two fragile things at once: the RTV skin around a narrow undercut (finger, ear, weapon) and the casting that comes out of it—plaster that chips, or PU that you yank while it's still green. The decisions are wet mass (even a 220 mm bust is kilograms of slurry), undercut peel vs split, a mother-mold jacket so Shore 10A–20A doesn't balloon, and a seam that misses the face. One-piece gloves that look cheap in a photo get cut apart on the first pull.

RUUIPON builds these as custom RTV tools in Bao'an, Shenzhen (since 2018): photos, sketch, or CAD, then a 3D-printed pattern, often a temporary silicone flip, a resin production mother, then batch RTV with a planned peel or split and a rigid support shell. Prototype 3–7 days after CAD lock; MOQ 20 molds per design. This is not an LSR cold-runner *part* tool. If the master is a print, finish it before anyone pours—layer lines become every casting.

Wet mass, undercut, jacket, Shore

Wet mass. Name the filled kilograms for the real material: gypsum, PU, or concrete-fill. A 220 mm figure can be 1–3 kg of plaster or a few hundred grams of PU; a larger bust climbs. Unsupported sag of about 0.5–1.5 mm is the conventional number on a tray-scale span. On a standing figure it shows up as a fat belly or a twisted stance if the jacket is missing. Design the jacket for the heaviest chemistry you will pour, not the empty rubber.

Undercut. Crossed arms, a staff, ears, and a deep cloak are not “the silicone will stretch.” If the peel would load a green plaster finger or tear the RTV, you need a keyed two-part, a removable plug, or a cut seam that you can live with in cleanup. Put the parting line behind the ears, down the back, or along a natural cloak edge—not across the face. See split lines and keys.

Jacket. Soft Shore 10A–20A skins for sculptural peel almost always sit in a plaster, GRP, or printed mother mold. The jacket splits on the same logic as the rubber so you're not prying. Details: mother mold / support shell. A solid RTV block is how shops hide a missing jacket, and it still creeps.

Shore. Typical cavity 10A–20A platinum so fingers and ears peel. Don't raise Shore to “hold the pose”—that's the jacket and the keys. A thick 25A wall can feel stiffer than a thin 40A lip; geometry first. Platinum shrink ~0.1–0.3%. If a base has to sit flat, put shrink on the master and measure a jacketed cast. ISO 3302-1 is a rubber-*part* class, not a figurine-mold slogan.

Master finish is part of tooling. SLA layer lines, sealer blush, and inhibition print into every face. Finish and barrier-coat before the pour. Options: master models.

Common mix-up

Sending a posed character render and asking for “one-piece, no seam.” Full-3D with a face means a seam *somewhere*. The job is to hide it. The other mix-up is copying a plaster-bust mold for a fast PU pull (or the reverse). Chemistry changes demold time and how much yank the casting can take—see plaster and PU resin.

Worked example: 220 mm standing figurine

Geometry: 220 mm tall, arms close to torso, show face is the front, base 70 mm, plaster or PU (buyer to lock).

Tool family: approved master (print artifacts gone, face signed off) → two-part platinum RTV Shore 10A–20A, keys, optional arm plug, vents at the head if PU → two-piece jacket → prototype in the *real* casting material → MOQ 20.

Acceptance: seam off the face and along an agreed line; fingers/ears survive demold; jacketed sag in the 0.5–1.5 mm typical band or better; no copied layer lines; registration returns after ten open/close cycles without a step in the seam.

If the pose adds a staff across the body, budget a plug. Don't stretch the two-part quote.

Failures you will actually see

Symptom	How to confirm	Fix
Seam steps across a cheek or forehead	First cast vs agreed line	Move the split; keys that actually register
Fingers, ears, or cloak points tear	Watch peel in the real material	Softer local peel, plug, or split; don't raise Shore
Face prints layer lines or pores	Raking light on master vs cast	Finish the master; don't recast a defective pattern
One-piece glove cut to get the figure out	The cut itself	Two-part from the start
Fat belly / twisted stance	Jacketed vs unjacketed pour	Mother mold for wet mass

A photo that would prove the claim: keyed split open with the face in one half, jacket closed, first cast with seam on the back. Request it at prototype.

Typical shop values

Reference values only. Confirm material-specific limits against the supplier’s technical data and agree project acceptance criteria before production.

Item	Typical shop value
Cavity Shore	10A–20A platinum RTV, jacket behind it
Mix	Platinum 1:1 or 10:1 by grade; vacuum degas until the foam collapses
Linear shrink	~0.1–0.3% (platinum)
Loaded sag, unsupported	About 0.5–1.5 mm
Prototype	3–7 days after CAD lock
Production MOQ	20 molds per design

What to ask when you're buying

Where does the seam go, and can I see it on the master before pour?
Plaster, PU, or both—and which one is the acceptance test?
Which undercuts need plugs vs a two-part split?
Jacket for wet mass, even on “just a figurine”?
Who owns the master, keys, and jacket after the tooling charge?
Will the master be finished, or are we copying the print?

We would not recommend a one-piece glove for a posed full-3D figure. We would not skip the mother mold because the sculpture “isn't as heavy as a paver.” We would not raise Shore A first to hold the pose. We would not pour RTV against an unfinished SLA face. We would not treat plaster and PU as interchangeable on the same untested skin.

RUUIPON Mold Structure Decision:

Flat-back relief? - full-3D figure -> Deep undercuts / pose?
Deep undercuts / pose? - silicone can peel safely -> Open-back RTV
Deep undercuts / pose? - arms, ears, staff lock -> Two-part / removable plug
Wet casting or Shore 10A-20A? - tiny shallow badge -> Open-back RTV
Two-part / removable plug -> Mother mold / jacket required
Open-back RTV -> Wet casting or Shore 10A-20A?

When this page is the wrong quote

Open-back wall plaques with hangers belong on plaster and gypsum. Fast PU with a 3-minute pot life needs the vent discussion on polyurethane resin. A 40 mm board-game token with no face can be a simple open-back tray. Injection-molded plastic figures in the tens of thousands are not RTV. High-volume silicone *parts* are an LSR/HCR quote.

Sculpture / figurine RFQ — copy this

Artwork, STL, or physical sculpt; which is the master
Finished height; flat-back vs full-3D
Casting material (plaster, PU, other) and filled mass
Show face; forbidden seam zones
Undercuts, fingers, weapons, cloak
Master finish target (print artifacts not acceptable on the face)
Jacket yes; Shore if already validated
Prototype in the real material
Quantity: prototype + production (MOQ 20)
Ownership of master, keys, jacket; recast of the RTV skin
Current failure: seam on face, torn fingers, copied layer lines, belly

Send the sculpt or STL, the show-face constraint, and the casting material. [email protected] · +86 135 3006 2969 · Licheng Technology Industry Park, Xinhe Blvd, Shajing, Bao'an, Shenzhen.

Matched CTA: Send the pose, show-face seam constraint, and casting material for a split-and-jacket review. Contact / RFQ · master models · split lines.

FAQ

Can this be a one-piece mold if I don't want a seam? Full-3D with a face almost always has a seam. We hide it; we don't pretend a posed figure is an open-back tray. One-piece gloves get cut.

Where should the parting line go? Behind the ears, down the back, or along a cloak edge. Don't put it on the face. Keys keep the halves from stepping.

Do figurines still need a mother mold? If you pour wet plaster or a large PU block into Shore 10A–20A rubber, yes. Typical unsupported sag is about 0.5–1.5 mm—enough to fatten a belly.

Will a 3D print work as the master? Yes after you kill layer lines, seal, and barrier-coat. An unfinished print becomes every face you ship.

If I paid tooling, do I own the sculpt and the jacket? Only if the PO says so. Tooling charge is not unrestricted ownership. Recasts need the same master and keys.