In this guide
- Read the piece before you test it
- The four tests, at a glance
- Touchstone and acid: fast, and it leaves a mark
- XRF: no damage, but only skin deep
- Why a plated piece passes a surface test
- The assay that settles it — and consumes the sample
- Specific gravity: the test that catches a filled base
- What a purity check actually costs
- Questions we are asked
A customer puts an anklet on the counter and asks whether it is real silver. The honest first response is a question back: real as against what?
Three quite different things get called fake silver, and no single test catches all three. There is base metal wearing a coat of silver. There is genuine silver alloyed thinner than it claims — 800 sold as 925. And there is a solid-looking article that is a silver shell around a filler core, so the weight in your hand is not the weight of silver.
This guide covers the tests a jeweller actually runs and what each costs — in rupees, and in damage to the piece. The checks you can do at your own table are in how to know silver purity at home. This is our side of the counter.
Read the piece before you test it
Before anything is tested, the piece is read. It costs nothing and on a modern article it can end the question outright. A hallmarked silver article carries the BIS Standard Mark, the word SILVER, the purity grade and a six-digit HUID; put that HUID into the free BIS Care app and it returns the grade, the article type, the date of marking and the centre that tested it.
Then comes the part that surprises people. Silver hallmarking in India is voluntary — gold's has been compulsory in phases since 2021, silver's has not. Since September 2025 any silver that is hallmarked must carry the HUID, but a jeweller stays free not to hallmark silver at all, so most silver in circulation carries no BIS mark, and the absence of one proves nothing. Your grandmother's lamp is not suspect for being unmarked; it has simply never been tested by anybody.
A 925 punched into a clasp is a different thing again — the maker's own declaration, not a third party's finding after an assay. What the fineness numbers mean is set out in what silver purity numbers mean.
The one-sentence version
No test that reads only the outside of a piece can tell you what is inside it. Everything below follows from that one fact.
The four tests, at a glance
Four tests do essentially all the work in this trade. Two read a surface. One reads the whole object as a lump. Only one reads the metal itself — and it has to take some of that metal away to do it.
| Test | How deep it reads | What it costs the piece |
|---|---|---|
| Touchstone and acid | The exposed surface — or a filed notch, if one is cut | A streak of metal rubbed off; a small permanent notch where plating is suspected |
| XRF spectrometry | The top few tens of microns | Nothing |
| Specific gravity | The whole article, as a single average | Nothing |
| Chemical assay | The sampled metal, exactly | The sample is dissolved and gone |
Touchstone and acid: fast, and it leaves a mark
The touchstone is the oldest instrument in the shop and still the quickest. You rub the piece against a dark fine-grained stone until it leaves a streak of metal, then drop test acid on it and watch the colour.
The usual test acid for silver is nitric acid carrying potassium dichromate. On a streak with a great deal of silver in it the drop goes a strong red; as the fineness falls the red darkens towards brown; on base metal there is no red at all. That is the whole reading — a colour, judged by eye, in under a minute.
What it costs the piece is a mark. Rubbing a streak takes metal off the surface — invisible on the shank of a plain bangle, not invisible on a polished lamp. Worse, if a piece might be plated the streak is useless, because the streak is made of the coating. To get past that you have to file a notch deep enough to cut through the plating and test the metal underneath. The notch does not grow back.
What it cannot do is give you a number. Colour grading separates bands — high-fineness silver from sterling, sterling from 800, silver from brass. It will not settle 925 against 900. It is a screen, not a verdict.
XRF: no damage, but only skin deep
X-ray fluorescence changed counter testing, and its great virtue is that it takes nothing away. The machine fires X-rays at the piece; atoms in the metal fluoresce, each element at its own characteristic energy; a detector counts them and the software reports a composition. Seconds, no contact, no mark — and it reports every metal present, not only the silver.
This is the standard quick read, and it is the first instrument a BIS assaying centre reaches for. In the centre's own operating rules XRF is a gate rather than a verdict: an article whose reading comes back more than 5 parts per thousand below its declared fineness is returned to the jeweller without being assayed at all. The instrument decides what is worth testing properly.
Its limitation is physical and cannot be engineered away — it reads a skin. Instrument makers put the analysed depth in metal at a few tens of microns — a few hundredths of a millimetre, and strongly element-dependent at that. Everything below it is invisible to the machine.
That cuts both ways, and the second direction is the one nobody mentions. A perfectly honest sterling piece can read high. Silver work is annealed and pickled repeatedly while it is made, and pickling strips copper out of the surface, leaving a silver-rich skin that the instrument reads and reports faithfully. An XRF number a little above the true bulk fineness is not necessarily anyone cheating — it can be the making process showing up in the measurement. Same machine, same caveat, as old gold; the mechanics are in checking purity and caring for gold.
Why a plated piece passes a surface test
A silver-plated piece passes a surface test because the surface really is silver. There is no trick in the chemistry. Plating is a genuine layer of silver, microns thick, deposited electrically onto something else. Streak it, drip acid on it, point an XRF at it — everything those tests can reach is silver, and they report silver, correctly.
The body underneath is usually brass or nickel silver. Nickel silver — German silver, in the trade — contains no silver whatsoever: it is copper with zinc and nickel, white because of the nickel. EPNS on an old piece says exactly that: electroplated nickel silver, a silver skin over a silver-free body.
Whether a surface test catches it is arithmetic between two thicknesses. Thin decorative plating is thinner than the depth an XRF beam analyses, so the beam passes through, reads copper, zinc and nickel underneath, and gives the game away. Heavy electroplate laid on thicker than that depth defeats the beam, and the machine reports silver in good faith.
So what does a jeweller do? Three things, in order.
- Look at the wear points first. Clasps, the inside of a bangle, the underside of a lamp foot. Plating wears through where a piece rubs long before it fails anywhere else, and a warm yellow or dull grey showing through the white is the entire answer, free.
- Weigh it and displace it. Density reads the whole article rather than its skin, and plated brass is nowhere near the density of silver — caught without a mark.
- File a notch — with permission. Somewhere that will never be seen, deep enough to be through any coating, then acid on the metal exposed.
Step three is not optional in the hard cases. No non-destructive test is certain about what lies beneath a heavy coating. When a customer tells us not to mark a piece, we do not mark it — and the answer they get is correspondingly qualified. That trade is fair. It should just be made knowingly.
The assay that settles it — and consumes the sample
The definitive test is wet chemistry, not the fire assay most people picture. Cupellation — melting a sample in a bone-ash cupel and driving off the base metals — is the reference method for gold, under IS 1418. Silver has its own Indian Standard, IS 2113, and what settles silver fineness under it is a titration.
A sample is filed or drilled from the article and weighed. It is dissolved in nitric acid. The silver now in solution is titrated against a thiocyanate solution with an iron indicator, which turns the liquid red the moment the last of the silver has been precipitated out. The volume consumed gives the silver content, and the centre reports it in parts per thousand, as single and mean values. That is where 925 and 800 come from — they are assay results before they are stamps.
What it costs the piece is not negotiable. The assay is definitive precisely because it works on metal taken from inside the article, and that metal is dissolved and gone. There is no version of it that leaves the bulk untouched.
A centre must sample representatively and return the article within 48 hours of sampling, assaying and marking. Which tells you what a full assay is for: bullion, scrap, a lot of new work going for hallmarking, or a dispute where somebody needs a figure that will stand up. Not the anklet your daughter wears every day.
Specific gravity: the test that catches a filled base
The density test is the only common one that reads the whole object instead of its surface, which makes it the right tool for exactly one problem: an article heavier than the silver in it can account for.
The method is old and unglamorous. Weigh the piece dry, then weigh it again fully submerged, suspended on a thread. The difference is the weight of water displaced, and in grams that is also the volume in cubic centimetres. Dry weight divided by volume gives the density.
| Metal | Approximate density (g/cm³) |
|---|---|
| Fine silver | About 10.49 |
| Sterling silver (925) | Roughly 10.3–10.4 |
| Silver-plated brass | Roughly 8.4–8.7 |
The gap between silver and brass is wide enough that no careful weighing can miss it, and no surface treatment can disguise it. This is the test that catches a heavy article with a non-silver core — a lamp or candlestick base bulked out with pitch, cement or plaster so it stands steady, wearing a silver shell. Such pieces are sometimes honestly marked weighted or filled, and sometimes not. Either way the gross weight is not silver weight, which matters the moment a piece is valued for exchange.
Where it fails. Hollow ware and anything with an air void. Stone-set work. Lac-filled traditional pieces, where the fill is part of the construction. And, like the acid test, it does not grade purity — it answers is this silver, not how good is this silver.
For the heavy pooja articles families buy here — kuthuvilakku, the traditional oil lamp, along with kalash vessel sets and tumbler and davara sets — this is the test worth insisting on, because on those pieces weight is the price. Silver is sold by weight against the day's silver rate in Vellore, so a filled base is no small matter. The range we keep is on our silver jewellery and pooja articles page.
What a purity check actually costs
There are two cost structures here, and they are not comparable. At a jeweller's counter the touchstone and the XRF read are ordinarily free — and not out of generosity. The shop is testing for its own account anyway. No jeweller buys old silver without knowing what is in it, so the test happens whether or not you ask. The only real question is whether you are shown the result. Ask to see the screen; nobody should feel awkward about it.
At a BIS recognised assaying and hallmarking centre the work is charged per article, and the centre must display its hallmarking charges on a board at the entrance — so the number is public before you hand anything over. BIS's published schedule lists ₹35 per silver article, subject to a minimum of ₹150 for a consignment, against ₹45 per article for gold with a ₹200 minimum, exclusive of tax.
Three caveats, and they all matter. Those are jeweller-side hallmarking charges, not a walk-in testing fee. BIS does publish a ₹200 consumer testing charge, but it is stated for a fire assay under IS 1418 — the gold standard — and we could not find an equivalent published figure for silver. The centre's obligation to verify purity for a consumer is written for jewellery that is already hallmarked, so an unmarked heirloom is a request, not an entitlement. And the pages carrying these rupee figures still refer to service tax, which tells you how long they have sat unrevised. Treat them as the published schedule, not as today's quotation, and ring the centre before you travel.
Before deciding a test is not worth the money: if a hallmarked article turns out to be of lower purity than its mark, the rules entitle the buyer to compensation of twice the amount of the difference — reckoned on the shortage of purity for the weight sold — plus the testing charges. The test pays for itself in exactly the case where you needed it.
Our own practice, for context: the purity of the article goes on the bill, and the rate is confirmed at the time of billing at the showroom.
Questions we are asked
Can silver purity be checked without marking the piece?
Up to a point. XRF and the density test leave nothing behind, and between them they catch plated base metal and a filled core. Neither can prove what lies under a heavy coating, and neither will separate 925 from 900. For a number that settles the question, metal has to be taken from the piece.
Can I take a silver piece to a BIS hallmarking centre myself?
Ask the centre before you travel. A recognised assaying and hallmarking centre must display its hallmarking charges at the entrance, but its published obligation to verify purity for a consumer is written for jewellery that is already hallmarked, so an unmarked heirloom is a request rather than an entitlement. The consumer testing charge of ₹200 that BIS publishes is stated for a fire assay under IS 1418, the gold standard, and we could not find a published equivalent for silver.
Does a 925 stamp mean the piece has been tested?
Not by itself. A 925 punched into a clasp is the maker's declaration about their own metal. A BIS hallmark is a third party's finding after an assay, and it carries a HUID you can check yourself in the BIS Care app. On a small piece the two look similar. They are not the same thing.
Will testing damage a silver lamp or an anklet?
The XRF reading and the water displacement test leave no mark at all. The acid test needs a filed notch if plating is suspected, which we would place where it cannot be seen and would not attempt on chased or stone-set work without asking first. A full assay consumes a sample and is not appropriate for a piece you mean to keep wearing or using.
Bring the piece in and we will tell you what it is
We assess purity and weight in front of you, we will say which test we are using and why, and we will not put a mark on anything without asking you first. There is no charge for finding out what you own.