CARBIDE LOT CERTIFICATION GUIDE

An assay is a laboratory test run on a sample of your material. The lab grinds or melts a small, representative piece of the lot and reports what is actually in it. For tungsten carbide, the numbers that run the price are tungsten (W) and cobalt (Co) — clean solid carbide typically reads around 85–94% tungsten with the cobalt binder making up most of the rest. The certificate that reports that test should carry all of this:

• The lab's name — a real, findable testing laboratory, ideally with an accreditation note.
• A report or certificate number — the document's own identity, so it can be traced and re-issued.
• A lot ID and a sample ID — the chain that ties this paper to one specific pile of material.
• The sampling method — how many drums, how many points, and how the sample was prepared. This is the field that matters most and gets skipped most.
• The test date — close to when the lot was assembled, not years before it.
• The lot weights — gross and net, so the paper and the scale can be reconciled.
• The elemental results — tungsten and cobalt first, plus iron, titanium, tantalum, or anything else the lab found, stated to a sensible precision.

Here is the sentence that protects you in every certified deal: the certificate describes the sample that was tested, from the lot named on it — nothing else. A beautiful assay for Lot A says nothing about Lot B, even if both lots came out of the same shop in the same month.

Matching a lot to its paper takes two minutes. The lot ID on the certificate should match the tags or markings on the drums. The drum count and net weight on the paper should reconcile with what is actually there — close is fine, since material settles and scales differ, but a paper weight that is double the physical weight is a different lot's paper. The material description should match what you see: a certificate for clean inserts does not describe drums of mixed sludge. When all four line up — ID, count, weight, description — the paper is doing its job.

Sampling decides everything.

The strongest certificate from the best lab still rests on one thing: the sample. A proper sample for a multi-drum lot pulls material from several drums and from the top, middle, and bottom of each, then blends and grinds it so the tested spoonful honestly represents the whole lot. A weak sample is one scoop off the top of the nearest drum — it describes that scoop, and a lot can be arranged so the top scoop is the best material in the building. When you read a certificate, the sampling line is the one to read twice. When you commission one, the sampling is the part to watch with your own eyes.

• The lot ID does not match. The certificate names a lot, a seller, or a location that is not the material being sold.
• No sampling method is stated. Results without a sampling story are numbers about an unknown spoonful.
• Suspiciously round results. Real assays read like measurements — 92.13%, 6.18%. A certificate that reads exactly 90.00% tungsten and 10.00% cobalt was typed, not tested.
• The date is wrong for the lot. A test dated before the lot existed, or years before the sale, describes material that had a different life.
• The lab cannot be found. No address, no accreditation, no way to call and confirm the report number.
• A fresh check gets resisted. Honest paper survives verification. Anyone confident in a certificate welcomes a split sample and a second reading.

The fix for every flag on this list is the same: verify the actual material. Paper starts the conversation; the scale and the analyzer finish it.

When I buy a lot — certified or not — the verification happens in the open, in front of the seller. Your lot goes on a digital scale you can read yourself. I spot-check with a handheld XRF analyzer across several drums and at different depths, so one friendly corner of one drum cannot carry the whole lot. Heft and magnet checks backstop the analyzer: carbide runs about twice the density of steel and barely answers a magnet, and anything that fails those basics gets separated and priced as what it is.

Then it goes in writing: an itemized weight receipt, form by form, with the per-pound number for each form and the total. We agree the settlement is built on net accepted weight before money moves. In person, I pay cash on the spot. On a shipped lot, I pay immediately — the moment you ship, while you are still at the counter. Clean solid carbide pays my published $18–$27 a pound, and the paper — when there is paper — simply helps us both get to the right end of that range faster.

How sellers protect themselves.

Four habits cover almost everything. Keep a sealed split sample of any lot you had assayed, so a second test can settle any dispute. Photograph the drums, the tags, and the seals before the lot moves. Get the quote in writing, tied to the lot ID and the net weight, before the material leaves your floor. And sell to a buyer who verifies in front of you — a process you can watch beats a promise you cannot, every time.