The difference

XRF vs hallmark vs acid test: what each one really tells you

Read our reviews on TrustpilotIndependent written XRF reportA test result, not a UK hallmarkYour item returned tracked, postage includedNo obligation to sell

Three methods, three jobs. A hallmark is a legal minimum-standard guarantee applied by an Assay Office. An acid test is a quick destructive screen used by jewellers and pawnbrokers. XRF is a non-destructive composition measurement. None replaces the others; each has its own use.

If I already have a hallmark, do I still need an XRF test?Sometimes. For a standard 9ct or 18ct item where you are confident in the hallmark and you only need to confirm the carat band, the hallmark is enough. For inherited pieces with worn or foreign hallmarks, for repaired pieces, or for items being passed through probate or insurance where the actual content matters, the XRF test is the better tool.

Ask first, post later

Start with a question, not a parcel. Send a photo on WhatsApp or call, and you will get a straight answer on what testing tier suits your item and what the report will cover. None of it commits you to posting anything.

This is a UK-wide postal testing service. There is no shop to visit and no counter. Wherever you live, the process is the same: ask first, then decide.

A hallmark

A UK hallmark is a set of legally-controlled marks applied to a precious metal item by one of the four UK Assay Offices: London (Goldsmiths'), Birmingham, Sheffield or Edinburgh. The Hallmarking Act 1973 reserves these marks. Anyone in trade selling a precious-metal item above the minimum weight without one commits an offence under the Act.

The mark guarantees that the item meets a legal minimum standard of purity (e.g. 375 ppt for 9ct gold). It does not say what the actual content is; the actual content could be 375 ppt or it could be 390 ppt, the mark is a floor, not a measurement.

A hallmark is also a record. It identifies the Assay Office that tested the item, the year it was marked, and (where present) the maker / sponsor. Antique hallmarks are themselves valuable historical records.

An acid test

A traditional acid test involves filing a small mark into the item to reveal the metal underneath, then applying a calibrated nitric acid to that mark and observing the reaction. The reaction colour and rate indicate the carat range of the gold. Cheaper and faster than XRF, used widely in pawnshops, jewellers and gold-buying counters before XRF became affordable.

It has three limits. It is destructive (the filed mark is permanent), it is operator-dependent (the result varies with technique and acid age), and it is an approximation (it puts the item into a carat range, not a parts-per-thousand reading).

On most modern Niton-equipped buyers, acid tests are kept for special cases, heavily plated suspects where XRF is being defeated by plating thickness, rather than as the primary method.

An XRF test

XRF spectrometry is non-destructive, fast, and reads the actual elemental composition of the metal, every element, in parts per thousand. Where the hallmark gives a legal floor and the acid test gives a carat range, XRF gives the measured composition itself.

It does have limits worth knowing. It reads only the surface and a short depth into the metal, so heavy plating can occasionally mimic solid metal on a single scan. The SOP defence is a multi-point scan trace (readings at face, edge and corners) which exposes plating signatures cleanly.

It also does not read inside a closed bezel-set stone, and it does not read non-metallic materials. For stones, the in-house gem service is the right tool.

When each method is right

QuestionHallmarkAcid testXRF
Does this meet a legal standard?Yes, that is what it does.Roughly.Yes, and shows by how much.
What is the actual fine gold content?No, guarantees a floor only.No, gives a carat range.Yes, to parts per thousand.
Is this plated or solid?The hallmark may indicate, if present and trusted.Yes, after the filing.Yes, with multi-point scan.
Will my item be marked or damaged?No, applied by the Assay Office.Yes, small filed area.No, non-destructive.
What other metals are in the alloy?No.No.Yes, every element shown.
Is it valid in court / probate / insurance?Yes, legal mark.Not on its own.As a written composition record, yes; it does not replace a formal probate or reinstatement valuation, and court admissibility depends on the proceeding.

Insurance and tracking

Your parcel travels on Royal Mail Special Delivery, and Royal Mail cover may be available up to £2,500 depending on the postal method and cover level used, and if a parcel may be worth more than that we split it across more than one prepaid label at no charge, each with its own tracking number and cover.

The label is Royal Mail Special Delivery Guaranteed by 1pm next working day, with full tracking and signature on receipt. The tracking link is emailed to you the moment the label is issued.

What you get back, and when

Your item is returned by Royal Mail Special Delivery on the same working day the report is issued. Return postage and its cover are included in the testing fee. There is no separate return charge.

If, for any reason, an item cannot be tested (badly damaged surface, non-metallic core, equipment misalignment), we tell you straight, refund the testing fee, and return the item the same day.

The independence pledge

You can use this testing service with no intention of selling, and plenty of customers do exactly that. Nobody here is paid more for turning a test into a sale. The report carries no offer and no upsell, because it is not the front end of anything. We test. What you do next is your own business.

Ask at the end whether the item is something we would buy and you will get an honest answer. Do not ask, and nothing follows.

What this report is, and what it is not

This is an independent XRF (X-ray fluorescence) compositional analysis report. It identifies the elemental composition of the item submitted. It is not a UK hallmark and does not replace the legal requirements of the Hallmarking Act 1973. UK hallmarks may only be applied by an authorised UK Assay Office.

The report identifies the elemental composition of an item to the accuracy of the analyser. It does not replace a UK hallmark, an Assay Office fire assay, or a written valuation from a qualified valuer for insurance reinstatement purposes. We say so in plain English on the front page of every report.

If a report leaves any doubt, we will tell you what the next step would be, typically a UK Assay Office fire assay (destructive but definitive) for high-value disputes, or a written insurance valuation from a qualified independent valuer for reinstatement cover.

Why sellers choose GoldPaid

GoldPaid is a small, owner-run UK business built on one promise: show the working. Every item is XRF-assayed and weighed on calibrated scales. Every offer is itemised in writing. Postage is free and tracked both ways, and there is never a countdown or a hard sell. If something is worth more to a specialist than to us, we say so.

Common questions

Is an acid test enough to know whether to sell my piece?

For a binary "solid or not" question, an acid test will get you most of the way there but it leaves a filed mark on the item. The plating check at £25 is the same binary question, non-destructively, with a written report.

Can XRF and a hallmark disagree?

Sometimes, and when they do, the XRF reading is usually correct. The most common cause is replaced parts (a chain hallmarked 9ct with a 14ct repaired clasp) or solder joints diluting the average. The multi-point scan trace usually finds the disagreement.

Is fire assay better than XRF?

For a definitive, court-grade reading on a single sample, yes. Fire assay is destructive (it consumes a sample taken from the item) and is the reference method the UK Assay Offices use for disputes. For a non-destructive, written composition record across multiple items, XRF is the right tool. The report identifies the fire assay route as the next step on contested high-value items.

Why do you not offer acid testing?

Because the customer is paying for an honest, non-destructive report. Filing a mark into an inherited piece to get a less precise result than XRF would be the wrong service for the customer.

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.

Request a prepaid Royal Mail label for your XRF test

Two quick steps. Tell us which pack you want in the box below and we will confirm the price and how to pay before anything is charged. The label itself is prepaid and costs you nothing, and your items are returned to you free once the report is issued. Testing is a separate, paid service: if you are here to sell rather than to have items tested, the assay is free as part of selling and how it works is the page you want.

Two things worth knowing before you start, rather than after. Everyone sends a photo of a UK passport or driving licence, whatever the parcel is worth — it applies to every seller, so it is never a comment on you. And the parcel is handed in at a Post Office counter rather than dropped in a postbox: the receipt they give you is the proof of postage any compensation claim depends on.

Step 1: What are you sending, and how should the label arrive?

A rough description is plenty. This helps us confirm the right postal cover level before we issue the label. Skip if you would rather not say — the field is optional.

How would you like the label to arrive? Both are prepaid and both use Royal Mail Special Delivery Guaranteed, so pick whichever is easier. The QR code is already selected because it needs no printer, and you can change your mind later — just message us before you post.

Choose how your prepaid label arrives

Step 2: Where do we send it?

Your label arrives by email whichever format you chose, so nothing is posted out to you. We need your address because it prints on the label itself, and because it is where anything you decline is returned. UK addresses only.

Needed so the label can be addressed to you.

Would you rather ask a question first, or send a photo? Message us on WhatsApp. It is the fastest way to get a sense of what something is worth before you post anything.

Related pages

Independent XRF analysis, by post

Message us before you order a test

WhatsApp a clear photo and any question you have. We confirm the pack, the price and what the report will show, and you decide whether to order.

Prepaid Royal Mail Special Delivery label and tracked return included in the pack price. We confirm the price before anything is charged. The result is an independent written report, not an offer to buy, and you are never obliged to sell.