Platinum vs Tin RTV for Resin Craft Molds | RUUIPON

Pick the cavity chemistry from the dump and the master, not from a kit label. For resin figurines, craft soap, pillar candles, wax melts, plaster, and architectural concrete, platinum (addition-cure) RTV is the default when you need a library mold you can recast, low leftover odor, and a shrink band that stays put after a full cure. Tin (condensation-cure) RTV is the shop answer when the master is dirty, the run is short on purpose, and you can live with ongoing shrink plus a leftover smell in the first dumps.

This page is the resin/craft fork. Food-contact cavities have a separate document path (platinum, wash, extraction on the finished article). Do not treat this as that page. RUUIPON pours the tool in Bao'an / Shajing since 2018: master, mold box, A/B, vacuum degas, keys, jacket, recast. Prototype is 3–7 business days after CAD lock. Production MOQ is 20 pieces per design. Simple 3D is USD $50 when that CAD scope applies.

Does not apply when the silicone *is* the product (a gasket, a baby teether, an LSR keypad). That is a steel or aluminum tool and a wydsilicone.com parts quote. It also does not apply when you already locked a food-contact platinum tray and only want the 21 CFR 177.2600 packing list — send that RFQ to the food-mold desk, not this chemistry comparison.

What actually changes between the two drums

Platinum RTV is addition-cure. Mix is 1:1 or 10:1 by grade, by weight. Vacuum until the foam collapses, then pour. After a complete room-temperature or mild-oven cure, linear change on the rubber is typically about 0.1–0.3%. The cavity you recast next season is still the cavity you poured, provided you kept the unsanded master.

Tin RTV is condensation-cure, often 10:1. It is more tolerant of a sulfur clay, a dusty plaster master, or a print that was never sealed. Byproducts leave for weeks. The mold keeps moving in storage. Fine for a one-weekend concrete pour or a dirty architectural master you will not reopen in six months. Wrong for a resin SKU you intend to recast from the same tool next year.

Odor is a procurement fact, not a marketing adjective. New tin tools can leave a condensation smell in the first wax or resin dumps. Platinum is quieter. If your buyer is a craft brand that ships unscented soy wax, tin leftover is a return, not a "cure longer" note.

Inhibition: the resin/craft failure, not a food lecture

Platinum RTV fails in a specific way: the face against the master stays tacky while the back of the jacket is fully cured. That is inhibition, not "cheap silicone." Common masters that do it on this floor: some SLA/DLP resins (especially if you skipped UV post-cure and a barrier coat), sulfur-bearing clays, latex gloves, condensation-cure (tin) residue on a reused box, and certain amine coatings.

Tin RTV usually copies that dirty master. That is why shops reach for tin on a garage sculpture. The trade is mold life and dimensional drift, not a free pass on quality.

Confirm inhibition before you argue Shore. Press a clean nitrile (not latex) glove on the cavity face. If the print stays shiny and the back is dry, scrap the tool for any dump that needs a fully cured skin. We remake from a sealed or post-cured master. Tell us what the master was printed or modeled in — that sentence belongs on the RFQ.

The photo that would prove it: cavity face in raking light, a fingerprint that stays wet, jacket back that snaps clean. We are not attaching a staged lot photo here.

Typical shop values

Caption these as typical shop values, not a named PO or a lab report number.

When we would still pour tin — and when we would not

We would not recommend tin as a "cheaper platinum" for a resin jewelry line you will recast. You will pay the difference in warped cavities and a smell complaint.

We would not recommend platinum poured against an unsealed, fresh SLA master "because platinum is better." You will get a sticky face. Seal, UV post-cure, or barrier-coat the print first. See 3D-printed masters.

We would not recommend mixing a tin glove and a later platinum pour in the same box without a contamination plan. Tin residue is a platinum inhibitor.

We *would* quote tin for a short architectural concrete run off a dirty plaster master, when the buyer says the mold is disposable after the pour and size drift is acceptable. Write that sentence on the PO so purchasing does not reopen it as a library tool.

Worked example (anonymized)

A 90 mm resin figurine, deep undercut hair, 12 cavities, PU dump at room temp. The buyer sent an unsealed SLA master and asked for tin "because resin isn't food." We sealed the print, poured a platinum 15A skin in a keyed two-part with a rigid jacket, CAD-locked the split, and ran the prototype in the 3–7 business day window after that lock. First PU dump released. A parallel tin quote would have copied the print faster and then drifted. Production followed at MOQ 20 per design. The $50 3D line was not charged — they already had a watertight STL in millimetres.

Common mix-up: tin is for craft, platinum is for food

Purchasing bins the drums that way because the food page on this site (and every TDS) repeats platinum for food-contact. Craft is not a free tin zone. Craft is "what are you pouring, how long must the mold live, and what is the master made of." A soy-wax melt line and a UV-resin earring line both fail on leftover tin odor and on platinum inhibition if the master is wrong. Ask those two questions before the drum.

ISO 3302-1 M2 is a common default *drawing class* for a rubber article. It does not pick platinum or tin, and it is not another word for precision.

A tooling charge is not unrestricted ownership of the master or the CAD. If you need the pattern in your custody for a recast, say so on the PO.

What to ask when you're buying

• What will you dump (PU, epoxy, UV resin, wax, soap, plaster, concrete), and at what peak °C?
• What is the master (CNC, sealed SLA, clay, existing part), and has it been UV-post-cured / barrier-coated?
• Do you need to recast from this tool next season, or is the mold disposable after the run?
• Platinum or tin, mix 1:1 or 10:1, cavity Shore, jacket yes/no?
• Who keeps the unsanded master after the tooling charge?

A platinum glove on a hooked figurine still tears if you skipped the split. Chemistry does not delete a hook — mark structure on DFM before tooling.

flowchart TD
  A[Name the dump and the master] --> B{Need a library recast and low odor?}
  B -->|Yes| C[Platinum RTV]
  B -->|No, dirty master, short run| D[Tin RTV is in play]
  C --> E{Master SLA / sulfur / latex?}
  E -->|Yes| F[Seal, post-cure, or barrier coat first]
  E -->|No| G[Pour platinum after vacuum]
  D --> H[Write disposable + size-drift accepted on the PO]
  F --> G
  G --> I[CAD lock then 3-7 day prototype]
  H --> I

Related: resin / PU molds, epoxy resin molds, craft resin solutions, contact.

RFQ copy-pack — resin/craft chemistry

Copy this to [email protected]:

• Dump material and peak °C (PU / epoxy / UV / wax / soap / plaster / concrete)
• Master type and whether it is sealed / UV-post-cured
• Recast next season: yes/no (unsanded master custody)
• Preferred chemistry: platinum or tin, and why
• Cavity Shore target if you have one; jacket yes/no
• Files: STEP/STL in mm, or photos with a millimetre ruler, or a sample
• Quantity: prototype, then MOQ 20 per design
• Simple 3D: charge USD $50 only if that CAD scope applies

Matched next step: send dump + master notes, not a blank "platinum or tin?" chat. Phone +86 135 3006 2969. Licheng Technology Industry Park, Xinhe Blvd, Shajing, Baoan. If you actually need a molded silicone *part* in LSR or HCR, that RFQ leaves this site.

FAQ

Can I use tin RTV for resin jewelry if I am not selling food? You can, for a short run off a dirty master. For a recast library and low odor in UV or PU dumps, we spec platinum and seal the print. Craft-only does not make tin the default.

Will platinum always copy my SLA master better? Only if the print is fully UV-post-cured and barrier-coated. An unsealed SLA is a classic platinum inhibitor. Tin may copy it and then keep shrinking. Fix the master first.

Does tin shrink more than the 0.1–0.3% platinum band? Platinum after a full cure typically sits in that 0.1–0.3% band. Tin keeps moving as byproducts leave. Do not freeze a tin cavity as a library dimension you reopen in six months.

Can leftover tin in the box ruin a later platinum pour? Yes. Tin residue inhibits platinum. Clean or dedicated boxes, or write a contamination plan. Do not assume a wipe is enough.

Is the $50 3D fee how you pick platinum vs tin? No. USD $50 is simple 3D when that CAD scope applies — turning measured photos or a rough file into a model. Chemistry is a separate line: dump, master, recast intent. Prototype clock starts at CAD lock, not at the first email. Production stays MOQ 20 per design.