Reducing 24k gold?

Hi everybody,

I've been given some 24k gold from a client to make into a ring. I want to reduce the carat to 18k but haven't done this before and am not finding much help online. I know I have to multiply the weight by something...but that is the extent of what I know.

Can anybody help by posting the steps for doing this?

Thanks for your help in advance!

Alex

Hi Alex,

Here are some facts, 18ct. gold is an alloy of 75% of 24ct.(fine gold) mixed with 25% of other pure metals. Depending on the colour you want. A standard 18ct yellow gold would be 75% of pure gold (24ct.) alloyed to 15% fine copper and 10% fine silver. If you want a red gold just increase the fine copper percentage. If you want a pale gold, sometimes referred to as Green gold, then you can just add 25% fine silver to the 24K, I use this alloy for making small carved leaves on antique restoration jobs.
To be simpler, if you have been given 10 grams of 24ct., then you will need to melt it in a crucible with 1.5 grams of fine copper and 1 gram of fine silver. which will give you approximately 12.5 grams of 18ct. yellow gold.

I hope this all makes sense.

James

Quote:

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Originally Posted by Goldsmith

Hi Alex,

Here are some facts, 18ct. gold is an alloy of 75% of 24ct.(fine gold) mixed with 25% of other pure metals. Depending on the colour you want. A standard 18ct yellow gold would be 75% of pure gold (24ct.) alloyed to 15% fine copper and 10% fine silver. If you want a red gold just increase the fine copper percentage. If you want a pale gold, sometimes referred to as Green gold, then you can just add 25% fine silver to the 24K, I use this alloy for making small carved leaves on antique restoration jobs.
To be simpler, if you have been given 10 grams of 24ct., then you will need to melt it in a crucible with 1.5 grams of fine copper and 1 gram of fine silver. which will give you approximately 12.5 grams of 18ct. yellow gold.

I hope this all makes sense.

James

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That would make it 80% pure gold, i think
75% is 9.375g i think
Feeling very nervous challenging you james so preparing to eat humble pie

Quote:

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Originally Posted by trialuser

That would make it 80% pure gold, i think
75% is 9.375g i think
Feeling very nervous challenging you james so preparing to eat humble pie

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In my experience what you start off melting is not what you finish with, if you want to guarantee getting an 18ct. hallmark when melting your own alloys then be generous with your gold alloy to make sure it reaches 18ct. If it's 19ct. it will get an 18ct. hallmark but if it's 17ct. it will get a 14ct. hallmark. So it's best not to be too pedantic with percentages. I always add more than the 75% of fine gold to my melts and I have never been refused an 18ct. hallmark.

James

You could approach it differently by starting with 10g of 9ct gold. This contains 3.75g of pure gold.

Add15g more of pure gold and you have 18.75 g 0f pure gold in 25g of alloy.

Check my maths, but I make that .75, or three quarters pure gold. In other words 18ct. As James has said, to be sure you could slightly overdo it. Dennis.

I was taught that you should aim for a slightly higher %age allowing for inaccuracies within the weighing process. If your balance is accurate to the weights that you are using then that is OK but is it calibrated accurately, mine not, so aim for a richer melt.
Les

James, can you tell me what i am doing wrong please as I am having difficulty soldering a piece of 9ct bezel gold to a flat 9ct gold disc, (the disc is 2mm thick and soldered to a bangle, which is 1.50mm sterling silver). I have got 9ct hard solder and 9ct easy solder and neither will solder, by the time the gold disc gets hot enough for the solder to melt the bezel has melted too. i have done two gold bezels now and will have to make another one, but getting a bit fed up with trying to get the solder to melt, the bezel gets a nice cherry red but the solder hasnt melted. Cant very well use silver solder as it will show where it runs through the underneath of the bezel.

I always aim higher, what burns off in alloys and mixes cannot be guaranteed.....you need to be confident you have at least the minimum gold content....

Quote:

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Originally Posted by Goldsmith

Hi Alex,

Here are some facts, 18ct. gold is an alloy of 75% of 24ct.(fine gold) mixed with 25% of other pure metals. Depending on the colour you want. A standard 18ct yellow gold would be 75% of pure gold (24ct.) alloyed to 15% fine copper and 10% fine silver. If you want a red gold just increase the fine copper percentage. If you want a pale gold, sometimes referred to as Green gold, then you can just add 25% fine silver to the 24K, I use this alloy for making small carved leaves on antique restoration jobs.
To be simpler, if you have been given 10 grams of 24ct., then you will need to melt it in a crucible with 1.5 grams of fine copper and 1 gram of fine silver. which will give you approximately 12.5 grams of 18ct. yellow gold.

I hope this all makes sense.

James

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Hi James,

Thanks for sharing your info and everybody else that did as well. It makes a lot of sense.

Alex

Quote:

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Originally Posted by Patstone

James, can you tell me what i am doing wrong please as I am having difficulty soldering a piece of 9ct bezel gold to a flat 9ct gold disc, (the disc is 2mm thick and soldered to a bangle, which is 1.50mm sterling silver). I have got 9ct hard solder and 9ct easy solder and neither will solder, by the time the gold disc gets hot enough for the solder to melt the bezel has melted too. i have done two gold bezels now and will have to make another one, but getting a bit fed up with trying to get the solder to melt, the bezel gets a nice cherry red but the solder hasnt melted. Cant very well use silver solder as it will show where it runs through the underneath of the bezel.

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Pat, I am afraid that you have gone about this job the wrong way. You should have completed the gold soldering of the bezel onto it's backplate before soldering the gold onto the silver bangle. As you have now found out you need a tremendous amount of heat to make the solder flow when soldering the thin bezel onto what is 3,5mm. thick metals. If you cannot get someone to perhaps lazer the bezel in place, then a final desperate option is to solder a thin gold backplate to the bezel, pierce out the middle of the backplate leaving a 2mm. flate around the inside of the bezel base, polish the bezel, then you can use a few spots of super glue to attach the bezel in position to the gold plate on the cuff, then use a 1mm. drill and drill through the bezel backplate and also through the gold and silver of the cuff and finally rivet the lot together using silver wire.

Best of luck
James

James, could Pat maybe heat up the bangle enough to get the solder to run again and remove the gold backplate from the bangle and then do it in the correct order? I suppose she might need to remove all the solder but would that work?