HOW TO SOLDER FOR GOLD ?
Let’s quickly see what is meant by soldering :
By soldering we mean the joining of two or more metal parts in order to obtain a single, strong body. In this case we do this by preparing an alloy whose melting point is lower than the melting point of the alloy of the object to be soldered, and which allows the multiple metal parts to be joined together using heat.
This type of soldering, which is what we usually use in jewellery making, is called BRAZING SOLDERING.
And it is carried out by melting an alloy which, previously prepared in the form of a sheet or wire, is placed between the parts of metal to be soldered. The operation must be carried out with great care in all its steps, so that the weld is stable and strong, as there will be approximately 25% less resistance in the area of the welded object.
If you are interested in more about welding, see our article —–> WELDING
THE SOLDERING OF GOLD FORMULAS
Unlike silver, (but this rule is also valid for silver itself) the soldering agents for gold must have chemical-physical properties as similar as possible to the constituent alloys and to the title at which they have been prepared, (e.g. 750/°°° those of 18Kt gold) so as not to alter and maintain the title, malleability, hardness and colour of the alloy as much as possible.
It is also very important to avoid lowering the title of the object we are working on, whether it is a new jewel or a jewel being repaired or transformed.
Therefore, to avoid lowering the title of the solder to be prepared, we use the same amount in thousandths of gold, varying only the metals added in the solder alloy.
– We always reason in thousandths ( °°° )
– Chemical nomenclature : Au ( Gold ) Ag ( Silver ) Zn ( Zinc ) Cd ( Cadmium )
– Pdf ( Melting point
E.g. : soldering for gold at a fineness of 750/°°° composed of : 750 Au – 93 Cu – 43 Cd – 114 Ag = 1000
Or : 750 Au – 114 Cu – 136 Cd = 1000
Indicatively, to prepare standard solder for yellow gold, we can proceed with these parameters:
Au Ag Cu Zn Cd* PdF ( Melting point )
parts in /°°°( thousandths ) 750Au 83Ag 88Cu 4Zn 85Cd 822° ca PdF
parts in /°°° 750Au 80Ag 73Cu 5Zn 92Cd 808° ca PdF
parts in /°°° 750Au 53Ag 50Cu 4Zn 142Cd 785° ca PdF
*The use of cadmium ( Cd ) in soldering is now prohibited due to its toxicity and has therefore been replaced by other metals.
So as an alternative, we could prepare three grades of gold solder without using cadmium Cd as it is considered carcinogenic, by preparing it this way:
Au Ag Cu Zn PdF ( melting point )
Strong parts in /°°° 750Au 83Ag 88Cu 89Zn 850° ca PdF
Medium parts in /°°° 750Au 80Ag 73Cu 97Zn 830° ca PdF
Soft parts in /°°° 750Au 53Ag 50Cu 144Zn 799° ca PdF
GOLD SOLDERING PREPARATION PROCESS
In the preparation process, once the metals that make up the solder have been quantified in grams, we proceed to place Au Ag and Cu in the cup first, and during fusion when they have reached the PdF (melting point) and are liquid and well amalgamated, we are going to add Zn and Cd, because the latter have very low melting temperatures and therefore tend to evaporate quickly.
So, once these have been added at the end of the melting, also well amalgamated with the others, we proceed to pour them into the ingot, doing this quickly so that as little metal as possible evaporates so as not to alter the percentages contained in the alloy.
In conclusion, the preparation of solder for gold by temperature gradation as can be observed can be prepared in the goldsmith’s workshop without great difficulty, paying attention to the percentages and weights and the preparation procedure, experimenting according to one’s own working needs.
In the working environment where production processes have time and costs to be cut down, today we make use of ready-made soldering, designed by professionals in the sector, which offer high quality technical-practical solutions, speeding up jewellery processing times, allowing more accurate finishes, avoiding problems such as oxidation, toughness, crystallisation, porosity.
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Academy Of Goldsmith Arts