Hallmarking and solder

Was: Soldering tube settings together


To hopefully clear up the confusion about solder for hallmarking I
have copied below the table from the British Hallmarking Act which
defines the minimum purity of solder which may be used in articles
sent for hallmarking to any of the UK Assay Offices. In order to
achieve a reduced melting point the solder alloys will virtually
always have less precious metal in than the carat metal - the only
exception I know is maybe enamelling grade solder which is very hard
and so close to the melting point of the carat metal that can be
quite difficult to use. I have also copied below a table showing
representative alloy compositions for various grades of silver and
silver solders…


Precious metal fineness is expressed in parts per thousand by

GOLD 999 750
GOLD 990 750
GOLD 916 750
GOLD 750 750
GOLD 750 Filigree or watch case 740
GOLD 750 White 500
GOLD 585 Yellow, Red 585
GOLD 585 White 500
GOLD 375 375
SILVER 999 650
SILVER 958 650
SILVER 925 650
SILVER 800 650


Two or more of gold, silver, platinum and palladium to total 950


*The excessive use of solder is not permitted. *

Silver Type M.P. Deg C

95.84Ag, 4.16Cu Brittania Silver
92.5Ag, 7.5Cu Standard (sterling) silver 920
92.5Ag, 5.75Cu, 1.75Cd Standard cadmium silver
92Ag, 8Cu Silver-rupee 920
90Ag, 10Cu Silver U.S. coins 890
80Ag, 20Cu Jewelry 820
80Ag, 13Cu, 6.8Zn Silver solder, hard
70-5Ag, 20-3Cu, 5-7.5Zn Silver solder, medium
66Ag, 23Cu, 10Zn Silver solder, French
63Ag, 30Cu, 7.5Zn Silver solder, common
55Ag, 29Cu, 12Au, 5.5Zn Gold solder, very easy melt
70Ag, 25Pd, 5Co Platinum substitute (Cooper’s)
73Ag, 27Pt Platinum solder 1160
70 Ag, 25Pt, 5Ni Platinum substitute (Cooper’s)
66.7Ag, 33.3Pt Platinum silver 1230
40Ag, 40Sn, 14Cu, 6Zn Silver solder, Bu. Stands

this is from http://tinyurl.com/32d33b

and a little more… from Cupalloys web page

467 is a hall marking quality, cadmium free silver solder with a
minimum silver content of 67%.

It is available ex stock as wire 0.5mm dia in 1 metre lengths. Price
�4.80 per metre incl P&P

It is available, ex stock, in four grades - “Extra Easy”,
“Easy”, “Medium” and “Hard” to enable two joints to be made on
the same article. All have a narrow melting ranges to produce neat
strong joints.

“467 Extra Easy”
68%Ag 20% Zn 13% Cu
Melting Range 680 - 700 deg C

“467 Easy”
67% Ag 11% Zn 22% Cu
Melting range 700 - 720 deg C.

“467 Medium”
74%Ag 7% Zn 19% Cu

“467 Hard”
76% Ag 6% Zn 28% Cu
Melting range 750 - 780 deg C.

The alloys are available ex stock as wire 0.5mm dia x 1 metre
lengths. Price UKP4.50 per metre incl P&P

The “Easy” grade is also available in wire form at 0.25mm dia.
Price UKP3.70 per metre incl P&P.

Best wishes,
Ian W. Wright
Sheffield UK

It's a pity that none of the UK bullion suppliers seem to carry
plumb solder or even have heard of it, as it works beautifully and
is surely a better solder to use when having to send stuff off for
assay and hallmarking! 

Methinx that all the solder in the UK is plumb. Plumb is a
designation employed in the US. The US used to allow gold solders to
have less gold than their designated karats. You probably don’t have
solders that are designated cadmium free either, because cadmium is
a carcinogen that is allowed n US solders.

Cookson carries Hoover’s Plumb gold solder repackaged as fine gold
solder, fine silver solder…or they did a year or so ago RER

Hi Ian,

The assay offices always take a sample of the solder used and for
silver, whether of Sterling or Britannia standard, the solder must
be at least 650 parts per thousand pure. 

I know about hallmarking and its laws but I didn’t know about them
actually testing the solder joints, so thanks.

I practice all you say about soldering and always have done, apart
from painting with ochre. I use torch control to stop previous
joints from flowing and haven’t had a joint leak yet.

US plumb solder, however, is different from our solder. Plumb or
karat solder is the same karat as the metal it is to solder. So
plumb sterling solder contains 92.5% pure silver and the other metals
manipulate the melting point to a bit lower than that of sterling
silver. I used it for a few weeks while it lasted, and they were the
best solder joints I have ever achieved. No puddling, no jumping
away to a different place. Every joint went smoothly, running along
the joint or around a bezel by capillary action, etc. I will be
buying the solder from the US as it worked for me. Nobody in the UK
sells it and I have tried virtually every supplier now (almost) but
all they sell is the 67% silver solder which I am already using. None
of them have even heard of it and assume it must be a brand name but
top American jewellers won’t use anything else. John Donnivan uses it
exclusively and confirmed what I thought to be the case, ie. same
karat as the metal to be soldered.

But thanks for your recommendations. Manchester Minerals is a
supplier I’ve not yet used.


Thank you Ian for clearing up the permitted solders issue.

In order to achieve a reduced melting point the solder alloys will
virtually always have less precious metal in than the carat meta 

However, what you say in the above sentence is apparently not the
case. A number of American Orchidians have publicly confirmed what I
am saying about “plumb” solder and I’m not going out of my mind -
honestly, although it almost feels as though I am.

I don’t have a problem with using UK solder and understand that what
we sell has to pass assay standards but I have used this mysterious
plumb solder and it was such a joy to use that that is the reason for
my quest. It’s like looking for the Holy Graille!

I will carry on with the UK solder but if I get desperate I’ll buy it
from across the pond.

Thanks again for the very useful I’ll print it out and
keep it.


Well all I can tell you Bruce, is that I was sent the mysterious
plumb sterling solder by an American friend and was assured that it
was cadmium free and still 92.5% silver.

Our own Mr Donnivan uses plumb solder exclusively so it definitely
exists and I’ve used it too. I’m beginning to wish I’d never asked
this question as most American jewellers and all English jewellers
seem never to have heard of it and I feel as though people think I’m
going mad and am a bit confused!!!

It exists, I’ve used it, I liked it and I may well buy some more.

Thanks again.

UK solder is basically a mixture of silver and fine brass. Carat gold
solder varies in composition but has the same gold content as the
gold. The reduced melting point is normally achieved by having a
quantity of cadmium and tin in the alloy which would preclude you
from making your own as they are more volatile metals than silver
etc and Cd is particularly unhealthy for you. You can make your own
higher silver content solders by alloying you own using pure silver
and bronze or brass. Dont use plumbers or electrical brass as they
contain lead, try gunmetal. Will the end result be any better than
commercial solder? If you work with Britannia or enamelling silver
the answer can be yes but otherwise one has to wonder.


Hi Helen,

Otto Frei sells ‘Plumb solders’ but, as far as I can see, they only
refer to gold solders which are a little different to silver
solders. Gold solders are made to comply with the various carat
standards by varying the alloy content. The following is from a
jewellery FAQ on a website at ifsjewellery.com which may explain

  Plumb gold (KP): http://tinyurl.com/2fpum5 

  In general usage, it means gold that has the same purity as
  the mark stamped on it. Therefore, 14KP means gold jewelry
  which had been soldered could be stamped 14K. according to
  current US and Canadian law, the pure gold content must be
  within 3 parts per thousand of the stamped karat mark for
  unsoldered items and 7 parts per thousand for soldered items.
  This means that technically all marked gold sold now is plump
  gold. In reality, not all gold jewelry is. When jewelers
  describe their jewelry as plumb gold, they are emphasizing that
  they abide by the law. 

  In the US and Canada, gold solders have to comply with the
  plumb-gold laws. A 14K solder might range from 12 to 14K. If
  jewelers want specify that they want a solder which is actually
  14K they may request a plumb solder. _When you have repairs
  done you should ask if they will use a plumb solder! 

Best wishes,
Ian W. Wright
Sheffield UK

It’s sorted now thanks. The solder I have been searching for IS
"plumb" and NOT plumbers solder - it is 92.5% silver and contains NO
cadmium and I can get hold of it.

Thanks to all the people who helped with suggestions and those who
tried to help by basically saying it doesn’t exist :wink: