Silver Clay and Hallmarking - Silver Clay School

Silver Clay & Hallmarking


The tradition of hallmarking in the UK goes back to the 1300s; it was the early safeguard for any purchaser of precious metals to know that what they were buying was the real deal. This is a tradition that continues to this day and allows the consumer a sense of security when buying jewellery or precious metals.

Metals are rarely used in their purest form, instead it is normal for them to alloyed with other materials to achieve strength or durability. It’s extremely difficult for a layman to identify what percentage is metal as opposed to alloy. That’s where the Assay Office comes in. There are currently 4 Assay Offices around the country, in London, Edinburgh, Birmingham and Sheffield. These are all independently owned companies, not run or managed by the Government, overseen by the British Hallmarking Council who ensures that standards and processes are implemented and maintained.

Legally, you are required to get your pieces hallmarked if you describe them as silver, gold, palladium or platinum unless they are exempt. See below for more information about exemptions.

What’s a Hallmark?

The hallmark consists of 2 separate marks; the first is the makers mark known as the Sponsor’s Mark, which is the unique mark to identify who made the piece. The second is the Assay Office mark. The Assay Office mark guarantees the type of precious metal and its purity. This involves testing a microscopic amount of the metal to ensure that it is what it is meant to be. By this mark, they guarantee the metal’s authenticity. This document by Assayed Assured describes the hallmark in more detail.



Exemptions to a Hallmark

The exceptions to this rule are articles made from precious metal which fall below the minimum weight listed below;

  • Silver – 7.78g
  • Gold – 1g
  • Palladium – 1g
  • Platinum – 0.5g

Silver Clay and Hallmarking

One of the most frequent questions I get asked in my classes is whether silver clay can be hallmarked or not. Well the short answer to that is most definitely ‘YES!’

PMC+, PMC3, PMC Flex and ACS are both fine silver and can be hallmarked as 999 – that is 999 parts out of 1000 are silver.

PMC Sterling can be hallmarked as 925 – which means that 925 parts out of the 1000 are silver, with the other 75 being copper. Once a piece of silver clay is fired, it is silver pure or sterling and can be hallmarked as such.

If you are using an ‘enriched’ fine Silver Clay such as ACS950 or PMC Sterling OneFire, then you could go for either the Britannia silver mark which is 958 – meaning 958 parts out of the 1000 are silver or a 925 mark.

Technically for these products of Silver Clay – they have a higher silver content than that, but with assaying, it’s the MINIMUM silver content that matters. Obviously, both products are not 99% fine anymore – they have more copper content in them and therefore cannot be marked as fine. For your information; ACS 950 is 95% silver and 5% copper and PMC Sterling Onefire is 96% silver and 4% copper.

 Should you Hallmark?

If your piece is over 7.78g in weight, it must be hallmarked as a legal requirement. But anything under that weight is entirely up to you. Students I have talked to in the past have been really interested in hallmarking their work because it adds some sort of ‘authenticity’ or gravitas to their pieces.  They want to reassure their customers that what they are buying is the real thing. I made a decision early on in my jewellery making and selling career to have my own hallmark and make sure all pieces I sold were marked regardless of size. But there is a cost implication of course and that’s normally the second question I answer when talking about hallmarking.

 So what are the costs and the processes involved?

Costs vary with each Assay Office and if you are interested in setting up your own hallmark I would suggest that you contact your local office to find out their charges. The links are listed above in the Introduction section. What I can tell you is that there is a set up process with a one off cost as well as the ongoing costs of hallmarking batches.

Setting up your Hallmark

  • You need to choose a Sponsor or Maker’s Mark from a selection that the Assay Office will give you.
  • You will also make a decision on the size of the mark you wish to be applied to your pieces. Normally the marks that are applied to the piece are tiny for jewellery, but there are larger ones available for that can be used for larger pieces such as tableware.
  • Once you have chosen a mark, you need to purchase a punch. The Assay Office will arrange for this to be made for you
  • You will need to decide where to keep the punch. If you store it at the Assay Office, they will apply the mark for you. If you wish to keep your punch at home, you can apply the mark yourself.

Submitting your batch

  • Batch up your items into metal types and complete a Hall note, which is a form detailing the batch and its contents. The Hall Note should be submitted with your parcel.
  • Once the batch has been processed, the Assay Office will charge you for the following;
    • A batch charge which depends on the number of items within your batch. It is more cost effective to submit more items; the charge per item will be reduced significantly.
    • Per item for every piece to which they apply with your Sponsor’s Mark – this is optional and you can apply your own Sponsor’s Mark.
    • Per item for every piece to which they apply a Fineness / Assay mark.
    • Any return postage costs to you.

In conclusion, the bottom line is that there are legal requirements if you are selling your pieces as precious metal and they fall within the weight criteria. If you make tiny pieces, then you should be fine! But if you make jewellery to sell and you want to be hallmarked, hopefully this guide has given you some insight as to how this works.

Until next time!

Emma xx