How accurate is XRF, and how does it compare to an acid test?
This page explains how GoldPaid uses XRF when it values items you post to sell. If you want to compare XRF with a hallmark or an acid test before choosing, XRF, hallmark and acid test compared sets the three side by side.
Does it matter whether a gold buyer uses XRF?
| Method | Damages the item? | What it tells you |
|---|---|---|
| UK hallmark | No | That a UK assay office found the piece to be at least the marked standard when it was marked |
| Maker’s stamp, such as 14K | No | The maker’s own claim, not an independent test |
| Acid (touchstone) test | Yes, a scratch on a stone | A rough carat band at the point scratched |
| XRF | No | The metals present at each point tested; plating can hide what is underneath |
| Cupellation (fire assay) | Yes, a small sample is taken | The gold content of the sample. The London assay office uses it occasionally, alongside XRF |
What XRF actually measures
XRF stands for X-ray fluorescence. The analyser directs low-energy X-rays at your item, and the metals in it respond by emitting their own characteristic energy signature. The instrument reads that signature and reports the composition at the point tested: how much gold, silver, copper, zinc, nickel and so on is present. Because it reads the surface, a plated piece is also checked against its weight, wear points and marks.
The analyser we use
GoldPaid assays with a Thermo Scientific Niton XL2 handheld XRF analyser, which reads gold (Au), silver (Ag), platinum (Pt), palladium (Pd), copper (Cu) and zinc (Zn). On a clean, solid surface it reads gold content to roughly ±0.1 to ±0.5 per cent absolute, and every item is scanned at several points rather than once. A reading is not a hallmark, and it does not replace an assay office’s own testing and marking.
It does not damage your items
XRF is completely non-destructive. Your items are not scratched, filed, drilled or dipped in acid. They come back to you in exactly the condition you sent them, which matters if you decline the offer and want them returned.
Why it beats the acid test
The traditional acid test works by scratching the item onto a stone and applying acid. It gives an approximate carat range and it marks the item. XRF gives a precise percentage composition and leaves no trace. For anyone selling by weight, the difference between "roughly 9ct" and a measured purity figure is real money.
Hallmark versus XRF
| Hallmark | XRF assay |
|---|---|
| An assay office’s guarantee of the minimum standard when marked (a bare stamp is only the maker’s claim) | A direct reading of the piece |
| Applies to the item when it was marked | Reads the item as it is now |
| Does not reflect later solder or repairs | Picks up solder, repairs and mixed alloys at the points tested |
| Absent on many genuine items | Works with or without a hallmark |
A hallmark tells you what the piece was when it was marked. XRF tells you what is there now, at the points tested, which is what an offer should be built on.
What you receive
After the assay we send you a written breakdown of the composition we measured, alongside the weight and the offer it produces. If a result surprises you, you can ask us about it before you decide, and you are always free to decline and have your items returned free of charge.
Common questions
Does XRF damage my jewellery?
No. XRF is non-destructive. Nothing is scratched, filed or acid-tested. Items are returned in the condition you sent them.
Can XRF test items without a hallmark?
Yes. XRF measures the metal directly, so it works whether or not an item is hallmarked.
Is XRF more accurate than the acid test?
Yes. The acid test gives an approximate carat range and marks the item. XRF gives a precise composition and leaves no trace.
Will I see the XRF result?
Yes. You receive a written breakdown of the measured composition with your offer.
What is XRF gold testing and why does it matter?
XRF (X-ray fluorescence) testing fires low-energy X-rays at a precious-metal item and reads the elemental signature returned. It is non-destructive, takes seconds, and returns the gold, silver, platinum and base-metal percentages to within a fraction of one per cent. XRF is not a hallmark and does not replace one, although the Goldsmiths’ Company Assay Office in London now carries out the vast majority of its own assaying by XRF and uses destructive methods such as cupellation only occasionally.
How do gold buyers make sure purity tests are accurate?
XRF reads the surface, so a careful buyer tests more than one point on each piece and checks the analyser against reference samples of known purity. Each item is weighed separately and checked for plating, solder and repairs. Fire assay (ISO 11426) is the reference method, but it destroys a sample, so it suits refining rather than a valuation where items may be returned. GoldPaid XRF-tests every item and checks plated pieces against weight, wear points and marks.
Not the question you had? The full GoldPaid FAQ covers the rest, from postal cover and ID checks to what happens if you decline the offer.
Speak to us before you post
Please send us photos on WhatsApp, and we will help you. We give a rough estimate where possible and arrange postage with you after our conversation. Your final offer follows inspection.