Industrial vs Food-Grade Silicone: Real Differences

If you're quoting industrial versus food-contact silicone, translucent is not a compliance class.

Industrial silicone and food-contact silicone often share a polydimethylsiloxane backbone and a Shore A number. That's where the similarity stops. Food-grade is not a sticker on a drum. It's a formulation plus a cure plus a finished-article extraction result under a named regulation. Industrial grades are allowed to contain processing aids, fillers, and catalyst residues that those extractions will fail.

This split applies to molded OEM parts-HCR compression and LSR injection-and to some food-contact trays. An industrial 50A HCR gasket can outperform a food-contact 50A LSR on tear and still be illegal in a baking tray.

Translucent is not a food-contact class

A lot of RFQs treat “food-grade platinum” on a website as the spec. Color, smell, and catalyst family do not substitute for 21 CFR 177.2600 or LFGB/BfR XV paperwork on the article. Paying a tooling charge on a cover photo does not tell you which compound, post-cure, or pigment package you bought.

Why one baking mat gets three compound quotes

Say you need a 120 × 80 mm baking mat, Shore 50A, 300 first articles and about 15,000 a year, US and German retail.

For the 300, a shop may run an aluminum one-cavity HCR tool-or an RTV prototype mold only to check geometry, not to qualify food contact.

For a few thousand millable mats, you'll usually cut a heated two-plate HCR tool. Platinum HCR with a ventilated post-cure is the realistic food path; peroxide HCR is the harder sensory route.

If annual volume justifies LSR, the production tool needs cavity heat, gates, vents, and usually a cold-runner. Don't call that a “LIM hot tool.” The cavity is heated; the runner, when it's a cold-runner, is kept cool. Those three PDFs can all say “food-grade mold.” You're not buying the same asset, and a spatula-line certificate does not cover this mat.

Lot-file questions for food vs industrial

Before you compare prices, get answers on:

• Named standard and food type: 21 CFR 177.2600 (aqueous / fatty / dry) and/or LFGB + BfR XV?
• Process: HCR compression vs LSR injection (cold-runner vs dump-runner); is any RTV sample only a geometry check?
• Cure family (platinum vs peroxide), post-cure temperature/time/thickness, pigment freeze?
• Who owns the plates and inserts after the tooling charge, and can you move the tool?
• Will first-article inspection (FAI) run against a ballooned print, including ISO 3302-1 (M2 is a common default)?

If those lines are missing, the cheaper quote is usually the incomplete one.

Industrial and food-contact share a polymer backbone, not a spec

Unmix the processes before you unmix the grades.

• Tin-cure RTV: condensation, tin catalyst, byproduct leaving the network. Not the default food-contact path. Prototype prototype mold only.
• Platinum RTV: addition-cure, room temperature. Some food-contact mold rubbers live here after post-cure and article testing. Still a prototype mold or a jacket, not HCR/LSR steel.
• LSR: platinum, liquid, injection, heat. Common for food-contact consumer parts.
• HCR: millable, peroxide or platinum, compression or transfer. Common for sheets, gaskets, and some bakeware.

Industrial in a catalog usually means mechanical and thermal performance for non-food use. Carbon black, extending oils, non-food pigments, peroxide systems that leave aromatic residues, and recycle content may be in-bounds. No extraction ceiling is claimed.

Food-grade in a catalog, used correctly, means the article (or a representative article from that compound and process) has been tested to a food-contact rule. In the US, the rubber rule most often cited is 21 CFR 177.2600 (rubber articles intended for repeated use). In Germany and much of the EU buyer conversation, LFGB plus BfR Recommendation XV (silicones) sits on top of Regulation (EC) 1935/2004. Those are different tests. A pass on one is not a pass on the other.

Fillers, oils, and pigments industrial compounds may carry

The material differences that matter to a lab are mostly what can leave the rubber into food, not the Si-O backbone.

Industrial compounds may include:

• Extending fillers that raise hardness cheaply but raise extractables or leave a dusty face
• Plasticizing or processing fluids that bloom
• Pigments and masterbatches that were never screened for food contact
• Peroxide cure systems whose decomposition products need a thorough post-cure, and some that still fail sensory tests
• Mold-release and bloom additives that help demold industrial parts and then migrate

None of those are automatically illegal in a pump diaphragm or a machine bumper. They become the failure mode in a water or n-hexane extraction, or in an LFGB sensory check (taste/odor).

Food-contact compounds start narrower: listed or evaluated constituents, platinum addition-cure as the usual chemistry, controlled pigment packages, and a post-cure designed to drive off cyclics and catalyst residues. Peroxide HCR can be formulated for food contact. It is the harder sensory and volatiles path. Tin-cure RTV is the wrong starting chemistry for a food-contact article program.

Hardness still does not tell you the grade. Shore 70A industrial and Shore 70A food-contact can feel similar in the hand and diverge in a reflux flask.

Extraction testing food-contact cannot skip

21 CFR 177.2600 is not a recipe approval for a gum. It sets composition constraints and extraction limits on the finished rubber article in the form that will contact food.

For repeated-use rubber in contact with aqueous food, distilled water at reflux: total extractives not to exceed 20 mg/in² in the first 7 hours, and 1 mg/in² in the succeeding 2 hours.

For fatty food, n-hexane at reflux: 175 mg/in² in the first 7 hours, and 4 mg/in² in the succeeding 2 hours.

Dry-food use has a GMP/suitability statement rather than those two extraction ceilings. The regulation also expects the finished article to be thoroughly cleansed before food contact.

LFGB, via BfR XV for silicones, is a different stack: composition rules, volatile organic matter limits, migration against food simulants (commonly water, 3% acetic acid, and 95% ethanol, at time/temperature matching use), and a sensory (organoleptic) evaluation. A part that clears US extractables can still fail German sensory or volatiles if post-cure was short.

Neither test is a medical biocompatibility test. ISO 10993 and USP Class VI are a different conversation.

Typical HCR shrink is ~1.5-2.5%; LSR ~2-3%. Those numbers belong on the steel, not on the extraction certificate.

Platinum chemistry plus post-cure as the practical split

On the shop floor the split is usually:

1. 1. Catalyst family. Platinum addition-cure for food-contact parts. Industrial may be platinum, peroxide, or tin depending on the part.
2. 2. Post-cure. Food-contact articles almost always need a ventilated oven post-cure to drop volatiles before testing and before use. Skip it and you are testing (and selling) a different article than the data sheet implied. Thickness changes the required time. A thin LSR baby-product skin and a 20 mm industrial bumper do not share a bake.
3. 3. Pigment and additive freeze. Once a food-contact compound is qualified, you do not swap a cheaper red or a new release oil without retesting.
4. 4. Process identity. The test article must represent production: same compound lot logic, same cure, same post-cure, same cleaning. A compression-molded plaque does not automatically qualify an injection-molded bottle nipple.

Industrial production can skip that freeze. That's the cost advantage. It's also why you must not use the industrial leftover translucent for a baking mold.

Paperwork that belongs in the incoming lot file

Ask for, and file:

• The named standard (21 CFR 177.2600, LFGB/BfR XV, and the food types: aqueous, fatty, acidic, alcoholic)
• A test report on a finished article (or a defined test plaque from the production process), not a raw-gum statement
• Cure and post-cure used on that article (temperature, time, thickness)
• Compound identification and pigment package
• Whether the report is for the mold rubber, the molded consumer part, or both. A food-contact LSR spatula and a platinum RTV candy mold are different articles.

Refuse: food-grade platinum with no method; a certificate that tests only the base polymer; a tin-cure RTV sold as bakeware; an industrial HCR relabeled because it is the same Shore; a fake SGS report number.

When this article is the wrong quote

If you need a reusable RTV cavity (gummy, chocolate, resin) rather than a vulcanized silicone part, food-contact still matters on that jacket-but the quote is a master + box + jacket job, not HCR/LSR steel. If the part never sees food (a pump diaphragm, a machine bumper), don't buy a dual-market extraction package you will not use. Geometry can also override quantity: a mating food-contact gasket at a few thousand a year is still a food-contact HCR job, not a catalog ice tray.

Related reading: passing FDA 177.2600 and LFGB, medical-grade ISO 10993 vs USP Class VI, silicone mold tooling explained, HCR compression molding.

What to send for a food vs industrial quote

Copy this into the RFQ.

• STEP/STL and 2D with critical dimensions and a rubber tolerance class (often ISO 3302-1 M2)
• Markets: US / DE-EU / both; food types and use temperature (oven, boiling, freezer, dishwasher if claimed)
• What ships: molded silicone part, or a flexible cavity
• Target Shore A, polymer family (HCR / LSR), color, post-cure
• First quantity and annual quantity
• Process preference: HCR compression vs LSR injection (cold-runner vs dump-runner)
• Who should own plates/inserts after the tooling charge
• Explicit: food-contact is not ISO 10993, not USP Class VI, not a color

Send the STEP file, the market and food type, annual quantity, and HCR vs LSR preference. That is enough for a plate-stack sketch before anyone mills steel.

Do not run leftover industrial gum on a tray

Do not run an industrial HCR leftover as a baking mat because it is the same Shore, or cutting a steel LSR tool with a cold-runner before a 120 × 80 mm mat has run as a one-cavity HCR prototype mold-unless annual volume and automation are already on the PO. Do not treat a tooling charge as ownership. Do not accept a raw-gum statement as article testing.

WYD Prototype → Compression → LSR (use this on the RFQ, then ignore quantity if geometry disagrees):

Route the RFQ from what actually ships: if Reusable RTV cavity, go to an RTV master-and-jacket quote on the WYD quote form; if Molded silicone part, go to Food contact or industrial?; if Tens to low hundreds / validation, go to Aluminum one-cavity prototype mold; RTV geometry only; if Thousands, millable HCR, simple shut-off, go to HCR compression: mill, preform, flash land, deflash; if Higher annual, LSR grade, automation, go to LSR injection: cavity heat, gates, vents, cold-runner.

Geometry and what actually ships override the process name. A tiny food-contact gasket at 400 pcs/year is still a compression job. A deep undercut at 50,000 pcs still needs side actions no matter which rubber family you pick.

RFQ comparison bands: 120 × 80 mm baking mat

Route	Typical first qty	Hardware	Typical shrink allowance	Typical drawing class
RTV prototype mold / jacket	20-50	Master + box + jacket	Platinum RTV ~0.1-0.3%	Cavity, not a rubber-article class
HCR compression	Low thousands	Two-plate, flash land, platen or cartridge heat	~1.5-2.5%	ISO 3302-1 M2 unless the 2D says M1/M3
LSR + cold-runner	High annual, automation	Steel, cavity heat, gates/vents, cold-runner	~2-3% (grade/temp)	Same drawing class + FAI remeasure

These are shop-normal bands for RFQ comparison, not a named lot.

FAQ

Does translucent or platinum-cured on a website mean food-contact? No. Translucent is not a compliance class. Food-grade is a formulation plus a cure plus a finished-article extraction result under a named regulation. Color, smell, and catalyst family do not substitute for 21 CFR 177.2600 or LFGB/BfR XV paperwork on the article.

Can a US extraction pass stand in for LFGB? No, those are different tests. A pass on one is not a pass on the other. Dual-market programs run both; they do not nest. A part that clears US extractables can still fail German sensory or volatiles if post-cure was short.

Why can an industrial 50A HCR gasket outperform a food-contact 50A LSR on tear and still be illegal in a baking tray? Food-grade is not a ranking of better rubber. Industrial compounds may carry extending oils, unscreened pigments, peroxide residues, and bloom additives that those extractions will fail. Shore 70A industrial and Shore 70A food-contact can feel similar in the hand and diverge in a reflux flask.

Does ISO 10993 or USP Class VI count as food-grade paperwork? No. Neither food-contact test is a medical biocompatibility test, and the reverse is also true. File the named food-contact standard, the food types, and a report on a finished article from the production process.

Will a certificate on the factory spatula line cover a platinum RTV candy mold or this baking mat? No. A food-contact LSR spatula, a platinum RTV candy mold, and a compression HCR mat are different articles. Ask whether the report is for the mold rubber, the molded consumer part, or both, and refuse a raw-gum statement or an industrial HCR relabeled because it is the same Shore.