How much is carbide sludge worth? Here is the exact math.

Three numbers build your price

Every sludge lot comes down to three measurements, and I show you all three on the settlement so nothing is a mystery. Wet weight is what the drum weighs when it arrives — sludge plus coolant plus oil plus everything. Dry weight is what is left after the moisture and volatiles are driven off. Assay percentage is the laboratory result: what fraction of that dry material is actually tungsten carbide. Multiply dry weight by the assay percentage and you get contained tungsten — the pounds of real tungsten in your drum. That is the number that gets paid for, priced against the current tungsten market. Wet weight tells you the size of the drum. Contained tungsten tells you the size of the check.

Follow one drum through the math

Say you have a 55-gallon drum of grinding sludge that weighs 500 pounds wet. It gets dried, and the moisture and coolant bake off — you are left with 300 pounds of dry material. A lab sample goes in for assay, and the result comes back at 50 percent tungsten carbide. Multiply 300 pounds by 50 percent and you get 150 pounds of contained tungsten. That 150 pounds is what your drum is actually worth, priced at the current market for tungsten content on the day we settle. Notice what happened: the drum weighed 500 pounds, but only 150 pounds of it was payable tungsten. The other 350 pounds was coolant, oil, and moisture — weight you never get paid for, which is exactly why keeping sludge dry matters so much. Now run it the other way: the same 500-pound drum, but this one was drained properly and kept as carbide-only grinding sludge. It dries down to 350 pounds at 65 percent assay — that is 227 pounds of contained tungsten. Same size drum, dramatically different check. The difference is entirely in how the shop handled the material.

Five levers, all in your control

Solid tooling has a board price. Sludge has an assay.

You will notice I publish a firm per-pound price for clean sorted carbide inserts, end mills, and drills — $18 to $20 a pound, standing offer. Sludge does not work that way, and any buyer who quotes you a flat per-pound number on wet sludge is either guessing or shorting you. Two drums that weigh exactly the same can hold completely different amounts of tungsten, and only drying and assaying tells the truth. That is why sludge is always a custom quote: I estimate from your photos and the grinding operation behind the material, put a written number on it, and the final settlement follows the lab result with every line itemized. It is more work than a board price, but it is the only honest way to price a drum of mud — and it is how you make sure you get paid for every pound of tungsten you actually have. The full assay process is explained in contained tungsten, explained.

Read it like a shop owner

When your sludge settles, you get a report with four lines: wet weight received, dry weight after processing, assay percentage, and contained tungsten — then the total. If any buyer ever hands you a single number with no breakdown, that is a red flag. The breakdown is what proves the math, and it is also what lets you improve: if your dry weight is low, drain better; if your assay is low, separate your carbide grinding from your steel grinding. Every settlement teaches you how to make the next drum worth more. That feedback loop is worth real money over a year of grinding.

Want me to run your drums through the math? Text photos to 312-880-8174 — tell me the drum count, how full they are, and what you grind, and I will give you a custom quote.