An acid test kit costs £50 to £85 and tells a trained eye the carat of the metal it touches, to within about 5%, after you file through any plating. An electronic tester costs £350 to £700, reads yellow gold quickly and struggles with white metals and platinum. A handheld or benchtop XRF analyser costs £10,000 to £30,000, gives a full elemental breakdown in seconds, and still only reads the top 10 to 50 microns of the surface, so it can be fooled by thick plating and cannot see a tungsten core. No single instrument is enough for a counter that buys from the public; the sensible kit is an acid kit and a specific gravity set on day one, XRF when the volume justifies it, and a file for everything.

The comparison

Prices are UK retail where a UK supplier publishes one, checked 19 August 2026, and US list prices where the only published figures are American. XRF vendors in the UK quote on request.

Method What it costs (Aug 2026) Time per test What it tells you What it misses
Touchstone and acid kit £48.95 (Quicktest 3-bottle, Cousins UK) to £80.40 inc VAT (Troytest 5-bottle, Cooksongold); Quicktest quotes £52.50-£82.50 for its own kits 1-2 minutes Carat band of the metal at the filed spot: 9, 14, 18, 22ct; silver 925/800/500; platinum with the green bottle Anything below the surface you did not file; exact fineness; white golds and platinum are harder to read; destructive mark
Electronic (de-plating) tester, e.g. GemOro AuRACLE AGT3 Pro £675 inc VAT (Dynagem UK); Quicktest puts the class at £350-£600 Under a minute Karat reading 8K-24K and a gold percentage; flags plate and gold-filled on yellow gold Quicktest: "not reliable on platinum", inaccurate on white metals, cannot test silver, needs a filed spot; calibration standard extra
Specific gravity (hydrostatic weighing) Quicktest kit about £160-£169 incl. scales; bench densimeters £2,000-£3,000 3-5 minutes with averaging Density of the whole object, so it sees through plating on a solid piece Useless on hollow, stone-set or mixed-metal items; slow; 22ct vs tungsten-alloy forgeries close in density
Handheld XRF, e.g. Thermo Scientific Niton XL2 100P, Evident (Olympus) Vanta GX, Bruker S1 Titan, Hitachi X-MET8000 UK: quote on request (Niton UK). US list, Alloy Geek: Vanta GX $19,990, Niton XL2 100P $22,500, Bruker S1 Titan and X-MET8000 $39,995, Niton XL5 Plus $49,990; pre-owned XL2 100P $19,995. Quicktest: £10,000-£30,000 5-30 seconds Percentage of every element above magnesium at the surface: Au, Ag, Cu, Zn, Ni, Pd, Pt, Rh, W Only the top 10-50 microns; thick plating reads as solid; tungsten core under a gold shell invisible; small or curved pieces need care; radiation safety and training
Benchtop XRF, e.g. Niton DXL, Vanta Element US list: Niton DXL $24,500, Vanta Element $24,995 10-60 seconds Same as handheld with a shielded chamber and a camera for spot placement Same surface limit; not portable
Low-cost XRF (unbranded, mostly Chinese) eBay UK listings £600-£17,700; most units £6,000-£13,000 Seconds An elemental reading of unknown calibration Calibration, support, radiation certification and resale value are all in doubt
Coin and bar verifier, e.g. Sigma Metalytics PMV Trusti Metrix (UK distributor): Original £830, Investor £1,479, Pro £1,999, Pro with external bridge £2,599 (VAT status not stated) Seconds Electrical resistivity through the piece; catches tungsten-cored bars and wrong-alloy coins Not for jewellery - needs flat regular shapes; will not give a carat
Fire assay at an Assay Office Quicktest quotes about £80 a test; free in effect when selling to a refiner Days The definitive fineness Destructive; useless at the counter

What does an acid test actually tell you?

The touchstone method is the oldest and still the most common. You rub the piece on a black stone to leave a streak, or file a small notch, and apply acid of a known strength: 9ct acid dissolves anything under 9ct, 18ct acid anything under 18ct, and so on up the bottles. You watch for the streak fading or changing colour.

Quicktest, which supplies most UK pawnbrokers and gold buyers, says "results to within 5% can be achieved" and that "good eyesight and steady hand" are required (Quicktest, twelve methods). Its own guide to the kits is blunt about the main weakness: "You must file the item first ... so that you are testing whatever might be underneath any plating" (Quicktest, acid tests). A heavily plated brass bangle passes an unfiled acid test every time.

Acid is also poor on white gold (the nickel or palladium alloy confuses the colour change), on platinum (a separate bottle and experience) and on anything under a few grams where a filed notch costs a visible fraction of the piece.

Cost is not the issue. Cooksongold lists the Troytest 5-bottle set at £80.40 inc VAT, Cousins UK the Quicktest 3-bottle at £48.95 and Troytest 4-bottle at £63.50. Bottles need replacing roughly yearly and the acids are corrosive, so gloves, goggles and somewhere sensible to keep them are part of the kit.

What does an electronic gold tester add?

Electronic testers such as the GemOro AuRACLE AGT3 Pro measure the electrochemical behaviour of the metal under a probe and report a karat value. Dynagem UK lists the AGT3 Pro at £675 inc VAT and says it tests yellow gold from 8K to 24K plus platinum and "identifies non-gold, gold plate and gold-filled items", with a one-step calibration using an 18K reference that is sold separately (Dynagem).

The advantages are speed and no acid on the bench. The limits, per Quicktest's description of the class: "not reliable on platinum", inaccurate on white metals, cannot test silver, and you still need a filed spot because the probe reads the surface. For a counter seeing mostly yellow 9ct and 18ct it is a fair step up from acid for new staff. For one seeing white gold, platinum, silver and coins it replaces nothing.

What does XRF do that the others cannot?

X-ray fluorescence fires X-rays at the sample and reads the characteristic energies each element emits back. The result is a percentage breakdown - gold 37.4%, silver 10.1%, copper 48.2%, zinc 4.3% - in seconds, with no mark on the piece. It converts "about 9ct" into a number the refiner's assay will roughly agree with, and it catches under-carat alloys that pass acid.

The hardware costs are real. Niton UK's page for the XL2 100 gold kit lists what is in the case (analyser, two batteries, Pelican case) and no price (Niton UK). The only published figures are American: Alloy Geek, a US distributor, lists the Evident Vanta GX at $19,990, the Niton XL2 100P at $22,500, the Niton DXL benchtop at $24,500 and the Bruker S1 Titan and Hitachi X-MET8000 at $39,995, with pre-owned units from $16,990 (Alloy Geek, August 2026). Quicktest's UK ballpark of £10,000-£30,000 fits once shipping, duty and a UK service contract are added. Budget for the service contract; the X-ray tube is a consumable.

Unbranded units on eBay UK run from a few hundred pounds to £17,700, most between £6,000 and £13,000. Before buying one, ask who calibrated it against what reference standards, who services it in the UK, and whether it comes with the paperwork you need to hold an X-ray device on business premises.

What does XRF miss?

Three things, and they are the three that cost buyers money.

It reads the surface. Typical penetration in a gold matrix is 10 to 20 microns, up to about 50 in lighter alloys. A thick plate - heavy gold plating over brass, or a gold shell over tungsten - reads as solid gold if the plating is thicker than the beam can see through. The standard mitigation is to file a spot or test a worn edge and take the reading there, which makes the "non-destructive" claim slightly less true at a buying counter.

It cannot see a tungsten core. Tungsten's density (19.3 g/cm³) is close enough to gold's (19.3) that a plated tungsten bar passes specific gravity as well. XRF cannot see through the shell. That is why bullion desks run a Sigma Metalytics verifier, which measures electrical resistivity through the piece, alongside the XRF.

Geometry. Small items, curved surfaces, chains and stone-set mounts do not present a flat area to the window, and the reading drifts. Benchtop units with a camera help; handhelds in a hurry do not.

XRF is also an ionising radiation source, so it needs a radiation protection adviser, local rules and staff training. The suppliers help, but it is not plug-and-play.

Specific gravity still earns its place

The hydrostatic test - weigh dry, weigh suspended in water, divide - gives the density of the whole object, which is exactly what the surface methods lack. Quicktest's kit with scales is about £160-£169; dedicated densimeters are £2,000-£3,000. Quicktest calls it "fiddly" and says it needs several readings averaged, so it is slow for a busy counter. But on a solid plain band or a bar it is the cheapest way to see through plating, and it is the check that turns an acid "18ct" into a confident one.

Which does a counter actually need?

It depends on what crosses it.

Counter Minimum kit Upgrade when
Jeweller taking occasional scrap from existing customers Acid kit, loupe, magnet, 0.01 g scale, file Never, provided a refiner's assay is the final word and you price with headroom
Independent gold buyer or pawnbroker seeing public walk-ins daily Acid kit plus specific gravity set plus file, and an electronic tester for speed on yellow gold XRF when monthly purchases are consistently above a few hundred grams, or when white gold, platinum and coins are a regular part of the intake
Bullion or coin desk XRF plus a Sigma Metalytics verifier plus SG From day one - a single tungsten-cored kilo bar pays for all three
Refiner or high-volume buyer Benchtop XRF with chamber and camera, SG, fire assay relationship -

The reasoning is arithmetic. Our piece on how gold buyers make money puts the gross margin on a 20 g lot of 9ct at about £70. One plated bangle bought as 9ct at 20 g loses roughly £650. A £10,000-£20,000 XRF pays for itself after fifteen to thirty avoided mistakes, sooner if the mistakes are organised. A £60 acid kit, a £160 SG kit and the discipline to file every piece catch most of the same mistakes for £220, at the cost of two minutes per item.

Whatever you use, record the result against the purchase - method, reading, who tested - because the refiner's assay will eventually disagree with the counter, and the only way to tell whether it is the instrument, the operator or the supplier is to have the data.

What we could not verify

  • UK prices for branded XRF. Thermo Scientific (Niton UK), Evident, Bruker and Hitachi quote on request. The US list prices from Alloy Geek are the only published figures we found; UK landed cost will differ.
  • VAT status of the Sigma Metalytics prices at Trusti Metrix; the page does not say. Chards listed the PMV Pro as "coming soon" without a price on the day.
  • Penetration depth figures. The 10-50 micron range and the 10-20 micron figure for gold come from XRF vendors' technical guides, which we have no reason to doubt but which are not independent.
  • Electronic tester accuracy claims. GemOro's "20% improved accuracy" is the maker's own phrase; we found no independent test.

Sources

This is general information, not a product recommendation or a safety guide. Prices were taken from the suppliers' pages on 19 August 2026 and change without notice; VAT treatment varies by supplier. X-ray equipment carries legal obligations under the Ionising Radiations Regulations 2017 - take advice from the supplier and a radiation protection adviser before you install one.

Milleso's gold desk records the test method and reading against every counter purchase alongside weight, fineness and spot, so when the refiner's assay comes back you can see which lots, which tester and which member of staff the difference traces to.