Part 2: Red Gold’s Unique Properties and Working with Red Gold Alloys

Following from last week’s post we will share some information on working with red gold alloys, particularly tips around melting, cooling, and fabricating.

Common practice for red alloys after heating/annealing is to allow the metal to come off red before quenching.

Because of the quantities of Copper necessary for the colour of these alloys upon casting a large grain structure can occur. This can result in grain boundary separation/cracking.

Ways around this if applicable are pouring a smaller ingot or annealing the metal prior to working.

Some reds require air cooling after casting whereas others can be quenched once the red glow has dissipated or they can be immediately quenched into hot water.

Once an alloy has been worked down and annealed/heat treated then its structure can balance out to a more user friendly condition. This is the stage our customers would receive the metal.

So at this stage as an alternative to air cooling quenching in hot water can be beneficial as the element of shock is reduced.

Quenching into water that contains a small amount of alcohol i.e. 5% of methylated spirits or Isopropyl alcohol will help with surface oxidation.

All alloys behave differently.

Methodical testing will give definitive results. i.e. Air cooling/quenching but this is not always possible for a Jeweller who has limited product.

Breakdown should be restricted to 50% or twice the original length after elongation although some alloys respond better to higher percentages. Too little work and frequent annealing can have adverse effects.

Our general fabrication annealing temp. is 650˚c or by hand torch/eye a dull red. A controlled atmosphere always produces better results when annealing red alloys.

Here are links to websites where you can learn about soldering based on extensive testing on a range of different solders and alloys:

http://www.ganoksin.com/index.htm

http://www.santafesymposium.org/papers/index.php

Curb Chain: Diamond Cut (Unfinished)

This chain has been soldered and diamond-cut on a lathe. It has not been polished since and if you look closely you can see light drag marks where the diamond tooling tracked on the flat areas. What do you think of this raw, industrial looking chain?

This chain is awaiting polishing / finishing after the diamond cutting stage.

This chain is awaiting polishing / finishing after the diamond cutting stage.

Part 1: Red Gold’s Unique Properties and Working with Red Gold Alloys

With the increase in popularity of red gold alloys, we thought it would be appropriate to share some information about what makes these alloys unique and how to address challenges that arise from the special properties of red golds.

–        Composition of Red Gold Alloys.
Red gold alloys are characterised by a relatively high copper content. Copper has a higher melting temperature and different structure to gold and silver. This means that red golds can behave quite differently to most precious metal alloys. Lower carat red gold in particular may have a higher overall percentage content of copper, creating challenges when working the metal.

–        Difference between Rose, Pink and Red gold.
Typically, red golds are described as either Rose, Pink or Red. This may vary between suppliers and recipes and is mainly based on the colour. Here are some typical examples for 18 carat red golds:
18K Red gold: 75% gold, 25% copper
18K Rose gold: 75% gold, 22.25% copper, 2.75% silver
18K Pink gold: 75% gold, 20% copper, 5% silver

Next week we will share some information on working with red gold alloys, particularly tips around melting, cooling, and fabricating.

 

Flux or No Flux? Welding and Soldering Platinum

Credit: http://www.jmny.com/

Apart from the high temperatures involved, platinum alloys weld readily without the need for fluxes. Because filler metal, if needed, is the same as the components to be joined, it is easily possible to close the seam without any visible colour change. This is a decided advantage in sizing rings, for instance. Even so, it is good practice to minimise the amount of filler needed (whether welding or soldering) by making joints as closely and accurately as possible; platinum alloys do not readily bridge large gaps with filler metal (which is not pasty at any stage).

The absence of fluxes, except for the lowest melting point solders (where the flux is to protect the solder, not the platinum – see below table), means that the usual adhesiveness of flux cannot be used to support the solder paillons in place. In practice, a small amount of non-borate flux may be used for this purpose, although it is not necessary metallurgically. Alternatively, solder may be clipped in the joint or supported by a thin extension of stock wire that is allowed to melt free at the last moment.

Platinum Solder Guide