Platinum vs Tin Cure for Food-Contact Molds | RUUIPON
For food-contact RTV cavities we spec platinum, not tin. Why the catalyst path matters, which docs actually ship, and what to put on the RFQ before mix
Kyler Yang · Founder8 min read
For a food-contact RTV cavity — chocolate, gummy, ice, baking, popsicle — we spec platinum-cure rubber. We would not spec tin-cure for those food cavities. Platinum (addition cure) is the path that matches the document packs buyers actually need: 21 CFR 177.2600 is extraction of the finished article, not an FDA-approved factory stamp, and LFGB / BfR is a separate European pack. Tin-cure (condensation) is a craft chemistry with a different leftover profile, ongoing shrink, and a smell conversation we do not want sitting under couverture.
RUUIPON pours those platinum tools in Bao'an since 2018: master, box, A/B mixed 1:1 or 10:1, vacuum degas, post-cure when the PO asks for it. Prototype is 3–7 business days after CAD lock. Production is MOQ 20 pieces per design. Simple 3D is USD $50 when that CAD scope applies.
If you need a molded food-contact *part* (spatula, teether, lid), that is not this page. Send parts to wydsilicone.com. Longer food-doc walk-through: food-grade molds.
Does not apply when the dump is PU resin, plaster, concrete, or a candle you will never plate food on. Tin can be a legitimate craft conversation there — still name it, still do not borrow a food extraction PDF. Also does not apply to LSR food *parts* in steel. Different factory, different shrink.
What the catalyst is doing in the drum
Platinum RTV is addition-cure: two parts, often 1:1 or 10:1 by weight, no condensation by-product. Mix, vacuum, pour, cure. Linear shrink on platinum grades we use for cavities sits in a typical 0.1–0.3% band. Size holds in storage better than a tin skin that keeps shrinking for months.
Tin RTV is condensation-cure. It is more forgiving of a dirty master and of some sulfur-adjacent clays. It also keeps moving dimensionally, can leave a leftover odor, and is the chemistry hobby kits use when the listing says "food safe" with a smile. Forgiveness on the master is not a food-contact argument.
Inhibition is the platinum tax: sulfur clay, latex gloves, tin residues, and some SLA resins leave the cavity face sticky while the jacket back is fully cured. That mold is scrap for food. We remake from a sealed or post-cured master. Tell us what the master was printed in. The 3D-print version of this problem is printed masters.
Why tin stays off our food RFQs
We would not spec tin for a food cavity because the leftover and shrink story fights the document pack. 21 CFR 177.2600 is a finished-article extraction (water and n-hexane style conditions on *that* rubber article). A gum-supplier letter for a tin kit is formulation evidence, not a tray extraction. LFGB / BfR files do not transfer from a cousin grade you found in a ZIP.
Colorant and oil bleed are easier to hide in a cheap tin tray and harder to defend when a chocolate buyer tastes them. If you already own tin stock trays and they work for craft, keep them for craft. Do not ask us to "match that Shore in food tin." We will quote platinum and a jacket if the tray loads.
Post-cure and a first wash still belong on platinum food tools before the first dump — that is a separate article: post-cure before food contact. Catalyst choice is the RFQ line that has to be right before that bake.
Typical shop values
Caption: typical shop values. Not a named lot.
| Item | Platinum food cavity (what we quote) | Tin (craft only; we would not spec for food) |
|---|---|---|
| Cure | Addition, 1:1 or 10:1 by weight | Condensation, kit-dependent |
| Vacuum | Yes on food detail | Often skipped in hobby pours |
| Shrink | about 0.1–0.3% linear | Keeps moving; do not copy our master compensation |
| Food-doc path | 177.2600 extraction and/or LFGB on the named compound | Do not borrow a platinum PDF |
| Odor at first use | Low if washed and post-cured | Common leftover conversation |
| Master sensitivity | Inhibition on sulfur / some SLA | More forgiving, still not a food argument |
| Prototype | 3–7 business days after CAD lock | Not our food clock |
| MOQ | 20 pieces per design | Stock kits are not this PO |
Common mix-up: "FDA silicone" as a tin-kit PDF
A buyer forwards a one-page "FDA approved" sheet from a craft drum and asks us to pour 24 cavities to match. 21 CFR 177.2600 does not approve a factory and does not approve a cousin grade. We would not run that sheet as the food path. Name US retail, EU, or craft-only on the RFQ. Buyer-spec fields: food-grade buyer spec.
Worked example (anonymized)
A 16-cavity chocolate shell for US retail plus a later EU listing. The first RFQ said "food-grade tin, cheaper." We refused the tin line, quoted platinum 25A open-back with a jacket (loaded edge sag is often 0.5–1.5 mm), $50 CAD only because the shell STEP had no fill line, locked CAD, poured in the 3–7 business day window, and listed 177.2600 extraction on that compound plus an LFGB pack for the EU SKU. The craft resin version of the same shell, sold as a hobby mold with no food claim, could have been a different conversation. The chocolate SKU could not.
Craft tin is still a named choice, not a silent food substitute
If you are pouring PU, plaster, or a decorative candle, tin can be on the RFQ when you have a reason (dirty master, kit match, cost). Write it. Do not later move that skin onto a chocolate line and forward the craft TDS as a US retail pack. We recast food in platinum. MOQ 20 per design still applies. The $50 CAD still applies if the craft master was never dimensioned for a food logo that has to wash. Mix 1:1 or 10:1, shrink 0.1–0.3% on the platinum recast — do not keep the tin compensation.
We would not recommend
We would not spec tin-cure rubber for food cavities. Full stop on chocolate, gummy, ice, baking, and popsicle tools from this shop.
We would not recommend using a platinum food extraction PDF to bless a tin recast you poured in-house.
We would not recommend calling RUUIPON an FDA-approved factory. We pour a compound path. The extraction is on the article.
We would not recommend skipping vacuum on a food logo well because a tin hobby video did.
Comparison tool (copy onto the RFQ)
| RFQ line | What to write for food | What we will not accept |
|---|---|---|
| Cure system | Platinum RTV, mix 1:1 or 10:1 | "Food tin" / unspecified kit |
| Docs | 177.2600 on this article; LFGB if EU | "FDA factory" ; gum letter only |
| Master | CNC or sealed SLA, inhibition check | Sulfur clay, raw SLA |
| Structure | Open-back / split / jacket named | Shore-only |
| Clock | 3–7 business days after CAD lock | "Ship next week" with unlocked art |
| Qty | Prototype, then MOQ 20 / design | One tray as production |
flowchart TD
A[Food-contact RTV RFQ] --> B{Dump is chocolate / gummy / ice / baking?}
B -->|Yes| C[Platinum only — we would not spec tin]
B -->|No, craft resin/plaster| D[Name tin or platinum on purpose]
C --> E{Docs: US 177.2600 and/or EU LFGB?}
E -->|Named| F[Mix 1:1 or 10:1, vacuum, post-cure plan]
E -->|FDA factory stamp| G[Stop — that is not a document]
F --> H[CAD lock → 3–7 business days → MOQ 20]What to ask when you're buying
- Platinum or tin, written on the PO — not "food-grade" as a blur?
- Which extraction pack ships with *this* compound and color?
- Will the master be sealed if it is SLA, so platinum does not inhibit?
- Post-cure and first-wash required before your first dump?
- MOQ 20 per design after the witness food pour?
RFQ copy-pack (food catalyst)
Email [email protected]:
- Dump: chocolate / pectin / gelatin / batter / ice / other
- Market: US / EU / both / craft-only
- Cure: platinum (default here for food)
- Reports that must ship with the lot
- CAD state; $50 if we still model
- Prototype after lock, then MOQ 20 of that design
Matched next step: send dump + market + the report names. We will not quote tin for those food cavities. Phone +86 135 3006 2969. Desk: contact.
FAQ
Can tin-cure silicone be used for chocolate molds? We would not spec it for a food cavity from this shop. Platinum is the food path we will put on a PO. Craft resin is a different sentence.
Is platinum RTV the same as FDA approved? No. 21 CFR 177.2600 is extraction of a finished rubber article. It is not a factory stamp and it is not automatic because the drum said platinum.
Why do hobby molds use tin if food shops use platinum? Tin is cheaper, more forgiving of dirty masters, and common in kits. Those are craft reasons. They are not our food RFQ.
Does platinum shrink less than tin? Typical platinum cavity shrink is about 0.1–0.3% linear and holds better in storage. Tin keeps moving. Compensate the master for the chemistry you actually pour.
Will you mix platinum and tin in one tray? No. Residues from tin can inhibit platinum. If a previous tin skin contaminated the master, we seal or remake the master before a food pour.
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