Gold · July 31, 2026
Testing Gold: Acid, Electronic, XRF — What a Buyer Uses
Before anyone can price your gold, they have to prove what it is. The three testing methods a buyer uses, what each one sees, and what each one misses.
Market guide: This article explains valuation factors. It is not a customer testimonial, completed transaction, promise or appraisal.
No offer on gold means anything until the gold has been tested, because a karat stamp is a claim, not a certificate, and plating carries the same stamps as solid metal. A buyer's testing step is not an insult to your honesty; it is the foundation the entire price rests on, and understanding the methods lets you tell a thorough buyer from a careless one. There are three main ways a buyer verifies gold — the acid test, electronic testing, and X-ray fluorescence — and each sees something different, with real trade-offs between speed, accuracy, and whether the test marks your metal.
The acid test is the oldest and cheapest, and it is still widely used because it works. The buyer rubs the piece on a touchstone to leave a small streak of metal, then applies nitric acid solutions calibrated to different karats. Lower-karat gold and base metals react and dissolve; higher-karat gold resists. By finding the strongest acid the streak survives, the tester brackets the karat. It is quick and inexpensive, but it is somewhat destructive — it leaves a tiny scratch on the piece and consumes a speck of metal — and it reads only the surface, so a thick plating can fool it if the tester does not scratch deep enough.
That surface-only limitation is the acid test's real weakness and the reason a careful tester scratches through to base metal on a suspect piece. Gold-plated and gold-filled items can pass a shallow acid test because the acid only ever touches the gold layer on top. A good tester files a small notch or streaks deeply enough to reach beneath any plating, which is why acid testing is often paired with a magnet check and a look at the stamps. Used carefully it is reliable for solid pieces; used lazily it can misread plated junk as solid gold or, worse for you, misjudge the karat of real gold.
Electronic testers are the fast, non-marking middle option, and they work by measuring a physical property of the metal rather than dissolving it. Most gauge electrical conductivity or a related property, since gold alloys of different purities conduct differently, and they display an estimated karat in seconds without acid or scratches. They are convenient for quickly sorting a pile and screening for obvious plating, but they are sensitive to surface condition, to the exact alloy, and to the probe contact, and they are generally less definitive than a proper assay. They are a screening tool more than a final word, best confirmed by another method on valuable pieces.
X-ray fluorescence, or XRF, is the most informative method and increasingly the standard for serious buyers. An XRF analyzer bombards the metal with X-rays and reads the characteristic energy each element emits back, producing a breakdown of the actual elemental composition — not just gold content but the silver, copper, palladium, and other metals in the alloy — without scratching, dissolving, or otherwise marking the piece. It is fast, non-destructive, and quantitative, which is exactly what you want, and it is especially valuable for variable-purity material like dental gold where there is no reliable stamp to lean on.
XRF has one limitation worth knowing, and it is the mirror image of the acid test's: it also reads a surface layer, just a slightly deeper one. Because the analyzer measures the composition near the surface, a sufficiently thick plating could in principle skew the reading, so a careful operator interprets XRF results in light of the piece's weight, stamps, and a magnet check rather than trusting a single number blindly. In practice, combined with those sanity checks, XRF is the most accurate non-destructive tool available, which is why the best-equipped buyers use it as their primary method.
Notice the pattern across all three methods: no single test is perfect, and good buyers combine them. A magnet rules out a steel core in seconds. Weight and dimensions catch density fakes like tungsten. Acid confirms karat on a fresh, deep streak. Electronic testers sort quickly. XRF reads the actual alloy without damage. A buyer who leans on one method alone is more likely to be fooled than one who cross-checks, and the combination is what lets a buyer pay you confidently rather than building a cushion into the offer to cover the risk of misidentification.
This is why the testing step is something to welcome and even watch closely, not to rush past. A buyer who tests thoroughly and lets you see it is demonstrating that your offer is built on verified facts, and thorough testing tends to work in an honest seller's favor because it confirms exactly what your good gold is. Be wary instead of a buyer who barely tests, tests out of your sight, or quotes a flat low rate to avoid the work — that is where variable-purity and higher-karat pieces get underpaid. Our sell gold process uses non-destructive testing so pieces are priced on their real composition.
For you as the seller, the takeaways are practical. Expect your gold to be tested and do not be offended by it; prefer a buyer who uses non-destructive methods like XRF on pieces you want to keep unmarked; understand that dental gold and mixed scrap especially need real testing rather than an assumed rate; and watch that the testing happens in front of you. The method a buyer uses is a window into how seriously they take accuracy, and accuracy is what stands between you and either a misread karat or a padded margin. A buyer who tests well is a buyer you can trust to price well.