What 'Food-Grade Silicone' Has to Prove: FDA and LFGB

Ask ten Chinese molders whether their silicone is food grade and ten will say yes. Ask for the document and roughly three send something back. Of those three, two send a one-page certificate with a blue stamp, an eagle logo and the words "FDA Approved" — a document that cannot exist, because the US Food and Drug Administration does not approve, certify or register silicone compounds or the factories that mold them. Understanding food grade silicone FDA 21 CFR 177.2600 and LFGB compliance for molded parts starts with accepting that "food grade" on its own is a sales phrase. It becomes a technical claim only when it is attached to a named instrument, a named test, and a named part.

This matters outside the obvious kitchenware categories. Silicone parts that touch food incidentally — seals in dispensing equipment, cup holder liners in a vehicle, a sleeve that gets washed in a sink alongside dishes — end up in the same conversation, and buyers who assumed the raw compound's paperwork covered them find out at retailer onboarding that it does not.

The US route is a rule you comply with, not a certificate you receive

For rubber articles intended for repeated food contact, the relevant provision is 21 CFR 177.2600. It does two things. It sets out the base polymers and adjuvant substances permitted in the article's formulation, and it prescribes extraction testing on the finished article — the article is subjected to specified extraction media under specified conditions, and the extractable residue is measured against limits, with a separate and tighter limit for a successive extraction than for the first.

Three features of that structure decide whether a supplier's paperwork is worth anything:

• It is self-determined compliance. No agency issues a pass. The responsible party — normally the importer or brand owner — determines compliance and holds the evidence. A third-party laboratory report stating that a sample met the criteria of 21 CFR 177.2600 is the evidence. A certificate asserting government approval is not evidence of anything.
• The test subject is the finished article, in the form in which it will be used. Not a pellet of compound. Not a plaque molded by the raw-material supplier in Japan or Germany. Your part, from your mold, in your colour, at your wall thickness.
• The successive-extraction limit is the one that fails parts. The first extraction can carry away whatever the surface was holding. The second one measures what keeps coming out of the bulk. A part that was pressed and shipped without adequate post-cure passes nothing on the second pass, because there is a reservoir of low-molecular-weight material still diffusing to the surface.

Read the current text of the regulation for the actual media, times and numerical limits before you write any of them into a purchase order. They are specific, and quoting them from memory or from a supplier's marketing sheet is how a spec ends up unenforceable.

The German route is a different instrument entirely

LFGB — the Lebensmittel-, Bedarfsgegenstände- und Futtermittelgesetzbuch, Germany's food, consumer goods and feed code — is national legislation. It sets the legal duty: articles intended for food contact must not transfer constituents in quantities that endanger health or unacceptably change the food's composition, taste or smell. What it does not do is tell a laboratory what to measure.

That technical content comes from the BfR Recommendations, issued by the German Federal Institute for Risk Assessment. For silicone elastomers the relevant one is Recommendation XV (Silicones). It is a recommendation, not a binding standard — but in practice it is the yardstick German laboratories and German retail buyers apply, and a report saying "tested according to LFGB" without naming BfR XV is telling you very little.

The practical difference between the two routes, and the reason a part can pass one and fail the other:

The single most useful thing in that table is the row about what catches under-cured parts. The German route has an explicit volatile-content criterion. The US route reaches the same physical problem indirectly, through the successive extraction. That is why a molder can honestly report a passing US extraction result on a thin part and then fail a German volatiles test on a thick one from the same compound.

Post-cure is the process step that decides the outcome

Here is the mechanism, because it is the part almost no sourcing article explains and the part that determines whether any of the above is achievable.

A silicone part leaves the press cured but not finished. Depending on the cure system, what remains inside it includes decomposition byproducts of the curing agent — peroxide-cured high-consistency rubber leaves acidic residues that platinum addition cure largely does not — along with unreacted low-molecular-weight species and residual cyclic siloxanes carried through from polymerisation. These are volatile. They are also mobile: they diffuse through the elastomer toward any free surface, over weeks and months, at room temperature.

Post-cure (also called post-bake) is a secondary oven step, in a hot-air-circulating oven with active air exchange, that drives those volatiles out before the part ships. Compound datasheets commonly specify something in the region of a few hours at a couple of hundred degrees Celsius, but the number varies by compound, cure system and section thickness — take it from the datasheet for the actual compound, not from a general article.

Four things about post-cure that separate people who have run a silicone line from people who have read about one:

Air exchange matters more than setpoint. The purpose of the oven is to remove volatiles, and volatiles cannot leave a saturated atmosphere. An oven at the specified temperature with the damper closed and a densely packed rack will return parts that are hot and still loaded. A properly vented oven at the same temperature, with trays spaced, will not. When you audit, look at the exhaust and the loading pattern before you look at the controller.

Parts shrink in post-cure. Additional shrinkage occurs during the bake — small, but real, and on top of mold shrinkage. If your dimensional approval was done on green parts straight off the press and production ships post-cured, your cutouts move. Approve dimensions on post-cured samples or you will re-approve them later, unhappily.

Thickness changes everything. Diffusion path length is what governs how long the bake has to be. A 1.5 mm skin and a 6 mm reinforced corner bumper are not the same problem, and a schedule validated on the thin one does not validate the thick one. Where a case has both — most rugged cases do — the schedule has to suit the thickest section.

Post-cure costs money and time, so it gets skipped. It is oven capacity, energy, floor space and a day of work-in-progress. On a price-driven order with no test requirement in the contract, it is the first step to quietly disappear. This is precisely why the test report, not the promise, is the thing you buy. The upstream choice of molding process shapes what the bake has to remove — the comparison of compression molding versus LSR injection sets out how the two routes differ on cure chemistry and residuals.

WJM Silicone's published capability text names food-grade and industrial silicone compression molding, temperature and pressure controlled, among its processes, and lists food-grade silicone among the materials it works with. Treat that the way you would treat any supplier's own description of scope: it tells you what to ask about, not what has been proven. The factory's own credential page states that certificate details remain pending verification, and nothing published shows a food-contact extraction report on a finished part. That is the gap your document request has to close.

The scoping trap: what a report actually covers

A food-contact test report is scoped to a specimen. Change any of the following and the report no longer covers what you are buying:

• The compound, including a change of grade from the same supplier.
• The pigment or masterbatch. A colour change is a formulation change. Heavy-metal and extractables behaviour follows the pigment, and a report on a natural translucent part covers nothing about your black or your safety orange.
• The cure system. Peroxide and platinum cure leave different residues.
• Wall thickness and part geometry, for the reasons above.
• Secondary operations. Printing inks, adhesives on a bonded assembly, and surface coatings all introduce substances the base compound report never saw.

So the correct request is not "send me your LFGB certificate". It is: a report from a named laboratory, dated, naming the test standard, naming the compound and colour, describing the specimen in a way that matches the part you are buying, and stating the results against the limits rather than only "pass". If reading these documents critically is new territory, the guide to how to read a China certificate of conformity covers the common failure modes, and the broader document request list for a first order puts this one in context.

Common questions

Is the raw-material supplier's food-grade declaration enough?

It is necessary and not sufficient. A declaration from the compound maker establishes that the base polymer and adjuvants sit within the permitted lists — a real and useful input. It says nothing about your pigment, your cure conditions, your post-cure, or your part geometry, all of which are decided downstream in the molding plant. Collect both: the upstream declaration and a finished-part test report.

My part is a device case, not a food container. Do I need any of this?

Depends on your channel, not on your intent. Some retailers apply food-contact criteria to anything hand-held and washable as a general chemical-safety proxy, and some product categories drag it in — a cup holder liner or a dispensing seal is a food-contact part in practice whatever the catalogue calls it. Decide early, because retrofitting a post-cure step and a test programme onto a running order costs more than specifying it at RFQ.

Can I ask for both FDA and LFGB testing on one sample?

Yes, and it is usually the efficient move. A laboratory can run both programmes on specimens from the same molded lot. Insist that the specimens come from a production-condition lot — same mold, same press settings, same post-cure schedule — and not from a hand-made sample batch that received a longer bake than production will ever get. Sample-versus-production divergence is the oldest problem in this trade, and post-cure is one of the easiest places to hide it.

What to ask the supplier next

Write the outcome into the contract rather than the email thread: name the standard, name the compound and colour, name the acceptable laboratories, state that testing is on production-condition parts, state the retest trigger, and state who pays for retest. Note that a compound or colour change made for compliance reasons can also move the tariff classification, which is worth checking against the Section 301 exposure analysis before you approve it; contract language on certification generally is covered in the product certification overview.

Before tooling, send this:

1. The compound trade name, grade and supplier, plus the technical datasheet, for every silicone used in the part.
2. The raw-material food-grade declaration from that compound supplier, with issuer name and date.
3. The cure system — peroxide or platinum addition — stated explicitly.
4. The post-cure schedule the factory intends to run: oven type, temperature, dwell, air exchange, and how the rack is loaded.
5. A finished-part extraction report against a named standard, on a part matching your compound, colour and thickness — or a written quotation for producing one if none exists.
6. Confirmation that test specimens will come from a production-condition lot, with the press and oven settings recorded.
7. The pigment or masterbatch identity and its own compliance documentation.
8. A written change-notification undertaking: no change of compound, pigment, cure system or post-cure schedule without prior written notice.

Run that list against any molder you are considering. WJM Silicone is a workable example to practise on — a Shenzhen compression-molding plant whose published material list includes food-grade silicone and whose credential details are, by its own statement, still pending verification. You can review the scope on the WJM Silicone factory profile, then treat every item above as a document to be produced rather than a question to be answered in an email.