ASTM F136 vs F67 vs G23: What "Implant-Grade Titanium" Really Means

Search for titanium earrings and you'll be handed four different labels within the first page of results: implant grade, ASTM F136, G23, medical grade. Some listings stack all four.

Here's the short version. ASTM F136 and ASTM F67 are published material specifications — they define what the metal contains and what it has to be tested against. Grade 23 (G23) names a specific titanium alloy, which is accurate but doesn't tell you whether the material was supplied against an implant specification. "Medical grade" has no published definition at all.

Below is what each term actually tells you, what it doesn't, and the five questions that settle it before you buy.

"Implant Grade" Isn't a Standard by Itself

It's a descriptive phrase the industry uses for metal made to a published specification for materials intended to go inside the human body. The phrase itself isn't regulated. The specifications behind it are.

Those specifications are written by ASTM International, and they govern two things: exactly what the metal is made of, and how tightly that composition has to be controlled from batch to batch.

That second part is the whole point. Any factory can produce one clean batch of titanium. A material specification defines requirements every batch has to meet — and a mill certificate is the document showing that a particular batch was tested and met them.

So the useful question is never "is it implant grade." It's which specification.

For body jewelry, two of them matter.

ASTM F136 — Titanium Alloy (Ti-6Al-4V ELI)

This is the specification most flat-back earrings are made to, including everything TISTELLA sells.

F136 covers a titanium alloy: roughly 90% titanium, 6% aluminum, 4% vanadium. The "ELI" stands for Extra Low Interstitials — oxygen and iron in particular are held below the limits allowed in the conventional version of the same alloy. Lower interstitials improve ductility and resistance to fatigue cracking, which matters when a piece of metal will be bent, threaded, and flexed repeatedly.

In practical terms, F136 is strong. Strong enough to hold a 0.8mm post without deforming, to cut fine threads that don't strip, and to hold prong-set stones securely. That mechanical headroom is why it dominates jewelry with small parts and detailed settings.

ASTM F67 — Commercially Pure Titanium

F67 covers unalloyed titanium — at least 99% pure, no aluminum, no vanadium. It comes in Grades 1 through 4, which differ mainly in residual oxygen and iron content.

F67 is equally legitimate. It's widely used in dental implants and is accepted by the Association of Professional Piercers for initial piercings, exactly as F136 is. Anyone telling you F67 isn't implant grade is either misinformed or selling something.

What F67 gives up is strength. Pure titanium is softer than the alloy, which leaves manufacturers less mechanical headroom for fine threading, very thin posts, or precision stone settings. It's used in body jewelry constantly — more often in simple, substantial pieces than in delicate ones. That's a design constraint, not a safety one.

Where "G23" Fits In

This one causes the most confusion, and it's the label stamped across product photos from most Asian manufacturers.

G23 is short for Grade 23 — and Grade 23 is Ti-6Al-4V ELI, the same alloy ASTM F136 covers. The two terms describe the same metal from different angles: "Grade 23" names the alloy, "ASTM F136" names the implant specification that alloy can be supplied against.

So a listing marked "G23 Titanium / ASTM F136" isn't contradicting itself. It's saying the same thing twice.

But the two shouldn't be treated as interchangeable labels. Grade 23 names a material. ASTM F136 sets requirements that material has to be tested against, with a mill certificate documenting the result. A supplier can accurately call their metal Grade 23 without any batch ever having been supplied against the implant specification. The alloy is right; the documentation may not exist.

You can't resolve this from a product page. What you can do is notice which term a brand leads with, and whether they'll answer a direct question about material documentation.

Side by Side

	ASTM F136	ASTM F67
Material	Ti-6Al-4V ELI alloy	Commercially pure titanium
Grade designation	Grade 23	Grades 1–4
Composition	~90% Ti, 6% aluminum, 4% vanadium	99%+ titanium
Nickel as alloying element	None	None
Mechanical strength	High	Low to moderate
APP-accepted for initial piercings	Yes	Yes
Headroom for fine posts and set stones	Substantial	Limited

The Nickel Question

If you're reading this because your ears react to earrings, here is the short version: neither specification includes nickel as an intentional alloying element. Not F136, not F67. Nickel isn't part of either composition.

Trace residual elements can still be present, as they can in any refined metal, and both specifications cap those under their residual-element limits — documented on the mill certificate when one exists.

This is the structural difference between titanium and the material it's most often compared against. Surgical steel — 316L — contains 10 to 14% nickel by design. It's bound into the alloy and many people wear it without incident, but it's deliberately present rather than residual. We cover that comparison in detail in our titanium vs surgical steel guide.

Between F136 and F67 there's nothing to choose on composition. Choose based on what the jewelry needs to do structurally. And if you have a diagnosed nickel sensitivity, don't stop at "hypoallergenic" — that word identifies nothing. Ask what the earring is made from, and whether the answer covers every component.

Two Kinds of Coating, and Only One Is a Problem

Here's where labels get genuinely misleading, and it's worth being precise.

"Titanium-plated" or "titanium-coated" usually means a different base material with a titanium layer on the surface. That base is commonly steel or a brass alloy, and the listing rarely says which. Surface layers wear with use, and once one wears through, whatever the base metal contains is against your skin. For a nickel-sensitive wearer, this is the worst kind of listing: it reads as safe without being it. The question to ask isn't about the coating — it's what's underneath.

Decorative PVD over solid implant-grade titanium is a different thing entirely. Gold-toned titanium jewelry, including ours, is implant-grade titanium with 18K gold applied by physical vapor deposition — a colour layer bonded to a titanium body. The distinction that matters for your skin is the base material: with titanium-plated steel, the base is the concern. With PVD over titanium, the base is titanium whether the finish is pristine or worn.

One language point worth separating out: gold-toned titanium is not solid gold jewelry. If a listing says "18K gold," check whether it means solid gold, gold-filled, plating, or PVD. All four are legitimate at their respective prices. Only vagueness isn't.

And One Label That Isn't Titanium At All

"Titanium steel" appears on a very large number of jewelry listings, particularly on marketplace and dropship storefronts. It sounds like a titanium alloy. It isn't one.

There is no such material. Titanium and steel don't form a standard alloy — the two metals produce brittle compounds when combined, which is why they can't even be reliably welded to each other. What "titanium steel" almost always describes is stainless steel, relabelled to borrow titanium's reputation.

That matters more than it might seem. Stainless steel is a legitimate jewelry material with real advantages. But 316L contains 10 to 14% nickel by design. Someone with a nickel allergy who buys "titanium steel" believing they've bought titanium has bought the one thing they were trying to avoid — and they'll conclude they're allergic to titanium when they react.

The test is the same as everywhere else on this page: a real titanium listing names a grade or a standard. Grade 2, Grade 5, Grade 23, ASTM F67, ASTM F136. "Titanium steel" names nothing.

Five Questions That Settle It

"Is it titanium?" isn't enough. These five are:

1. Which titanium? ASTM F136, ASTM F67, or just "titanium"? A named specification is verifiable. "Medical grade," "surgical grade," and "skin friendly" are not — they aren't necessarily false, they just identify nothing. Watch for "titanium steel" in particular — it names no material at all.

2. Does the claim cover the whole earring? Decorative front, post, push-pin, flat-back disc, setting. A listing that specifies "titanium post" has told you about one component. The rest touch your skin too.

3. Solid, or coated? "Titanium" and "titanium-plated" are opposite claims. If a listing doesn't say, assume it's the one that costs less to make.

4. What does "gold" mean here? Solid gold, gold-filled, plating, and PVD are four different things at four different prices.

5. Will they answer? Ask which specification, whether it covers every component, and whether material documentation exists. How a brand responds tells you as much as what it says.

What This Means at TISTELLA

Every TISTELLA earring is ASTM F136 implant-grade titanium throughout — decorative front, post, push-pin, and flat-back disc. Not the post alone.

Gold colourways add an 18K PVD finish over that same titanium body. The base material doesn't change when you choose gold instead of silver; the colour does. Silver colourways are the natural finish of the metal, uncoated.

That's the complete answer to all five questions above. It's the answer you should be able to get from any brand you're considering.