Air-Dry Clay as a Porous RTV Mold Master | RUUIPON

Air-dry clay can be an RTV master if it is fully dry, sealed, and not a sulfur-bearing formula. Unsealed clay is a sponge: platinum soaks in, the face copies pores you did not sculpt, and addition-cure can inhibit against leftover moisture, plasticizers, or sulfur. We would rather reprint or CNC a production master from a scan than pour a library tool against a fragile original you cannot recast when it cracks.

RUUIPON takes clay originals in Bao'an / Shajing since 2018, usually as a pattern to seal or to scan. Prototype 3–7 business days after CAD lock (the lock may be a scan of your clay). Production MOQ 20 pieces per design. Simple 3D is USD $50 when that CAD scope applies. Mix 1:1 or 10:1 by weight; platinum shrink about 0.1–0.3% after full cure. Clay is not a food-contact surface. Steel/LSR *parts* — wydsilicone.com.

Does not apply when the clay is already a finished art object you will not allow us to seal or scan. We cannot pour production platinum against a museum piece with no barrier. It also does not apply to polymer clays that stay sulfur-rich after bake — those need a barrier or a tin chemistry conversation, not a hopeful platinum pour.

Porous clay copies until it inhibits or sheds

Two different failures:

• Porosity / moisture. Air-dry clay that feels dry on the outside can still hold water. Platinum against a damp face skins poorly, copies bubbles, or stays tacky. Dry thoroughly, then seal. Sealer path is its own page: sealer on porous masters.
• Sulfur inhibition. Some modeling clays (the classic oil-based sulfur ones) poison addition-cure. The mold face against the clay stays wet; the back of the pour cures. A clean-lid patty of the same mix cures. That split is the tell — same diagnostic as sticky inhibition.

Oil-based sulfur clay is not "air-dry." Buyers mix the words. Ask for the brand family: water-based air-dry, polymer bake, or sulfur oil clay. We would not treat them as one master class.

Fragile originals: a pour-on box can destroy a thin clay ear. Brush-on detail coat plus a jacket, or a scan-and-print master, is how you keep the sculpture. Structure still follows the Mold Structure Decision once the master is stable.

flowchart TD
  A[Clay original] --> B{Sulfur oil clay?}
  B -->|yes| C[Barrier coat or do not pour platinum]
  B -->|no air-dry or polymer| D{Fully dry?}
  D -->|no| E[Dry first]
  D -->|yes| F[Seal; test a patch of platinum]
  F --> G{Patch cures on the face?}
  G -->|no| C
  G -->|yes| H[Scan for a library master or pour with care]
  H --> I[CAD lock then 3-7 day prototype]

The photo that would prove the master call: clay with a sealed half and a raw half, a platinum patch on each, only the sealed side dry. We are not attaching a staged lot.

Patch-test clay before you bury the sculpture

Mix a 10 g 1:1 or 10:1 shot. Dab a coin on a hidden land after sealer. If it stays tacky while a lid patty cures, do not bury the sculpture. Change sealer, dry longer, or scan. Do not add extra B.

A clay original also sheds grit. Fine sand in a cheap air-dry body becomes craters in the platinum face, then pimples on every resin dump. Seal does not hide grit; it can glue the grit in place. We wipe, then seal, then patch. If the sculpture is the art, we would rather scan and print a production master than keep pouring on a body that is still sloughing.

Do not box-pour a thin clay ear without a support. The hydrostatic head of platinum will fold the ear and you will copy the fold forever. Detail-coat the undercuts, or print a backed master. Permission to destroy a test ear should be in writing before mix day.

ISO 3302-1 M2 will not save a master that sheds grit into the face.

Shop numbers for clay masters

Caption: typical shop values, not a named PO.

Clay originals we would not pour against

We would not recommend platinum on unsealed, still-cool air-dry clay.

We would not recommend using the clay original as the only production master. It will nick. Scan or mold a sacrificial copy.

We would not recommend a food-contact tray poured on clay with no document path. Name 21 CFR 177.2600 on the article; the clay is not the food surface.

We would not recommend sulfur clay "because tin is more forgiving" as a silent swap on a library SKU. Write chemistry on the PO.

A tooling charge is not unrestricted ownership of your sculpture. If the original is one-of-a-kind, say so before we put it in a flask. Say whether we may seal, scan, or box it.

Worked example: 110 mm clay that inhibited until sealed

Figurine, 110 mm, water-based air-dry, still cool in the core. First platinum patch inhibited. Dried, sealed, second patch cured. We scanned, printed a sealed production master (USD $50 3D applied), poured a keyed 15A two-part with jacket. Prototype 3–7 business days after CAD lock of the scan. Production MOQ 20 of that design. The clay went home unsanded — it was never the library master.

Mix-up: treating the clay original as the production master

Artists want the first pour off the sculpture. Production wants a recast path. Those are two masters. The other mix-up is calling every brown clay "sulfur." Read the brand; test a patch.

Questions that keep clay from poisoning the pour

• Brand family: air-dry, polymer, sulfur oil clay?
• May we seal, scan, and keep a printed master?
• Food or craft dump?
• Open-back, split, or glove?
• Who keeps the original after the tooling charge?

Related: 3D-printed masters, figurine molds, contact.

RFQ copy-pack — clay master

Paste into [email protected]:

Object: RTV mold from a clay original, not an LSR/HCR part Clay family: air-dry / polymer / sulfur oil / unknown Permission: seal / scan / box (yes/no) Dump material and peak °C File: photos with a millimetre scale; ship the original only if agreed CAD: USD $50 3D if we scan and rebuild Prototype 3–7 business days after CAD lock, then MOQ 20 per design Patch-test platinum on a hidden land before a full pour

Send clay family and permission to scan. We patch-test — not a blank "free quote." Phone +86 135 3006 2969. Licheng Technology Industry Park, Xinhe Blvd, Shajing, Bao'an. Shop since 2018.

FAQ

Can I pour platinum straight on dry air-dry clay? Dry is necessary, not sufficient. Seal, then patch-test. Moisture and porosity still inhibit.

Is polymer clay safer than air-dry? Some bake clays are still inhibitors. Patch-test. Do not assume "baked" means platinum-safe.

Will tin-cure copy sulfur clay better? Often more tolerant, with ongoing shrink in storage. Wrong for a library SKU you recast next year — see tin shrink.

Can the clay be the food mold? No. Food contact is the cured platinum article plus documents, not the pattern.

If you scan my sculpture, who owns the CAD? A tooling charge is not unrestricted ownership of the scan. Write who keeps the file.