Tag Archives: london assay office

Goldsmiths’ Company event for students

.Yesterday and Friday the Worshipful Company of Goldsmiths and the London Assay Office held an event for UK jewellery students to learn about all sorts of businesses which support and supply their crafts and skills, from all about hallmarking itself to……pearls………..US!

outside the guild's hall

The flag’s out -outside the guild’s hall

Over the two days we’ve talked ourselves hoarse about pearls (my voice has dropped about an octave at least!) with students and with some of the leaders of the jewellery business in the country. I don’t know if I wasn’t more excited than many  of the students at who was there and who we met.

Through the imposing doors and up the sweeping staircase to our waiting stand, in the livery colour of crimson with Pearlescence in gold lettering, and under the crest of the livery company (www.thegoldsmiths.co.uk)- I know from a previous visit that security is very tight – it has to be because the London Assay Office, which checks and oversees the quality of £millions in precious metals is on the top floors.(www.thegoldsmiths.co.uk/welcome-to-the-assayoffice)

crest of the worshipful company of goldsmiths

crest of the worshipful company of goldsmiths

The Drawing Room is the room used by the film company to stand in for Buckingham Palace in the film The Queen, starring Helen Mirren. It’s all white and gold,

We set up and go round to see who else is here. It’s by invitation, and many of us are as stunned as I am to have been asked. There’s a big buzz of excitement…

The Drawing Room, Goldsmiths' Hall

The Drawing Room, Goldsmiths’ Hall

Pretty soon the students start to flood in and immediately home in on the fireballs I’ve brought. My aim in choosing what to bring was to keep it pared down and show that there is so much more to pearls than white and round and the fireballs and big ripples I selected start their job immediately. By the end of the two days I think I explained how fireballs happen at least once per hour! The students love them, and fireballs.

I did several knotting demonstrations as well during the two days. By the last one my co-ordination had gone completely and I got knots!

me plus demonstration table

me plus demonstration table

At the end, @goldpolisher and I both asked if we could keep our name labels from the front of our stands as souvenirs. We abruptly changed our minds though when it was pointed out that this would mean we would not be coming back. ‘Keep them…Please!’

Special thanks to @stevelao and Alison of the assay office, plus to the wonderful, unfailingly helpful, knowledgeable and friendly Goldsmiths’ Company and London Assay Office staff.

Most memorable moment…Looking at the panels on the wall listing the Masters of the Worshipful Company of Goldsmiths dating back to 1317 and realising that I’m standing right there – by invitation!

Behind securely closed doors: The London Assay Office

The London Assay office, where much of the gold, silver, platinum and palladium sold in the UK is hallmarked, lives on the third floor of the hall or headquarters of the Worshipful Company of Goldsmiths, a stone’s throw from St Paul’s Cathedral in the City of London.

Hall of The Worshipful Company of Goldsmiths

Hall of The Worshipful Company of Goldsmiths

I was fortunate to be one of the lucky few gold and silversmiths to be included in a party allowed in for a day to see the processes involved.


Hallmarking is the the oldest form of consumer protection in the UK, with Goldsmith’s  Guild getting its first royal charter from Edward III in 1327 (the guild HQ has been on the same site since 1339) . Now the guild, through the London Assay Office, is one of four independent

ceiling in main hall

The sumptuous ceiling in the main hall

organisations (also Birmingham, Sheffield and Edinburgh) which assay precious metals as required by the 1973 Hallmarking Act.

A hallmark is NOT a trademark. A hallmark is punched or lasered into the metal after the metal content is analysed and it is confirmed to be of a certain standard. Each hallmark tells you who made the piece or sent it for assay (the sponsor’s mark – Pearlescence’s is WMG in a cartouche shape)  what quality of what metal both in traditional and millesimal (figures) marks, which assay office and in what year.

The Assay office also conducts an annual examination of the coins manufactured by the Royal Mint (known as the Trial of the Pyx) and uses its huge collection of old silver items as a resource for the dating of suspect antiques. Two years ago the head of assay personally checked and hallmarked every gold and silver medal for the London Olympics.

Modern Hallmarking

It seems astonishing that every item sent in for assay is individually checked…but it is. A method dating back to Roman times, touch testing is the quickest and simplest.  Pearlescence’s silver ring was checked in a demonstration (no photos by me, unfortunately due to obvious security needs). In a method which ancient Romans and Egyptians would recognise and still be able to carry out, the piece is simply rubbed onto a highly polished tile of lydite until a 1cm by 2mm ish streak is made. Compare that with the streak made by a touch needle of known quality. check by a drop of acid on both. If they match you have identified the metal and its quality (in this case Sterling 925 silver)

The second ancient method is cupellation (which is a splendid word) and this method dates back to pre-Roman times. It is the most accurate. The gold sample is weighed very accurately then a known amount of silver is added in a process called inquartation. this mix is wrapped in lead foil and shaped into a ball, which is placed in a cupel. the cupel is put into a furnace for 20 minutes  and everything melts. everything except the pure gold and silver is absorbed into the cupel. Dissolve the silver in acid (parting) Weigh the remaining pure gold, subtract the known amount of silver and simple maths then gives the proportion of gold in the assay item. (accurate to one part per thousand)

hallmarking room.

This is the main hallmarking room. Very skilled

Finally there is the ultra modern x-ray fluorescence where an item is placed into a machine and bombarded with x-rays. The resulting spectrum identifies the metal and carat. Pearlescence tried this with some unknown gold made into a fused ring (9ct) and another ring made of silver wire and fused gold (interestingly the silver only came up to 800 proof with a lot of gold mixed in (so will be marked as silver), while the gold was over 18ct)

Once the items have passed assay they will be hallmarked. This, astonishingly, is still mostly done by hand. we had a go. It’s scary to try to put the London mark onto metal properly and cleanly. The brilliant folk in the photo above do it so well that even with the smallest punch you can still count the (three each side on the leopard’s face) vibrissae.

Alternately marks can be applied with a laser now or mechanically with a press for long runs of identical items

Hallmark being applied with a laser

Hallmark being applied with a laser

Top tip from the day – heartfelt plea from the assayers and markers…please do not pack each item into its own packet. We have instantly resolved to use those plastic compartment trays. Make your assayer love you!

An amazing day, I learned so much. And I even got a certificate!

certificate assay tour

Pearlescence got a certificate!