Aussie Lapidary Forum

LAPIDARY => Ask a "Silly" Question => Topic started by: tinker on June 23, 2019, 04:16:20 PM

Title: Moulding Gold
Post by: tinker on June 23, 2019, 04:16:20 PM
Hi Learned friends, I am attempting to pore molten gold into a mould to make a ring up have been unsuccessful.  I have attempted Cuttle fish moulds, clay mould and sand moulding with no success, can anybody give me some hints on how I can successfully produce a ring.  I have  previously had success with using Cuttle fish bone to mould stirling silver, but gold doesn't want to play the game. ???
Title: Re: Moulding Gold
Post by: Rusted on June 23, 2019, 05:05:33 PM
Google "Lost wax investment casting"

Short n sweet
Make a wax model
Attach to wax sprue, sprue will become hole that you pour the metal in
Submerge in investment. Investment is sort of like plaster of paris.
When set bake in kiln for 3 or 4 hours untill all moisture is removed and wax is burnt out
For a simple ring you could try just pouring molten gold into the hot investment mold
When the gold has turned solid dump the mold in a bucket of water while still very hot

Basically how it's done, obviously I have left a lot out which Dr google will show you.

Or

Pour your gold into a small bar, then hammer into a ring shape and solder the join, this might actually be the easiest to do as Gold is very malleable and easy to work.
Title: Re: Moulding Gold
Post by: FlashGP on June 24, 2019, 07:36:34 AM
You need to heat the cuttlefish mould before casting gold into it.  I have instructions on homesilversmithing on Google sites
Title: Re: Moulding Gold
Post by: tinker on June 24, 2019, 07:55:18 PM
Thanks everyone, I have tried the gold bar suggestion, but will have a go with the heated cuttle fish bone.  What did you heat the cuttle fish in.
Title: Re: Moulding Gold
Post by: FlashGP on June 24, 2019, 08:21:40 PM
Hi Tinker

I use a square of  screen mesh sitting on a small propane stove, the ones with dizposable gas canasters.

The cuttlefish mould sits i  a jam tin and is held in place with jasper geavel from the garden.

Then I place an upturned 3litre Golden Circle fruit juice tin over the jam tin to form a small oven.  Use a welding glove to remove the tin just before you pour the gold.

Put the burner under the tin on full blast until you are ready to pour, tgdn swigch off the burner and bring the cruicible to the mould, heating it as you go so ghe gold stays liquid.  Then line up and pour.

I get beginners to line up the mould and do a dummy run before starting fhe burner and melting the metal.  With small pours, 50 gms oe less, gold or silver freezes pretty quickly and you want the pour to go smoothly..

Here's a link to the site.  Read the safety first notes. From memory cuttlefish casting notes are under things to do.

https://sites.google.com/site/homesilversmith/for-beginner-silversmiths

Regards
Title: Re: Moulding Gold
Post by: tinker on June 24, 2019, 08:57:25 PM
Thanks Flash, I will give your method a go beers
Title: Re: Moulding Gold
Post by: Moth on June 25, 2019, 08:38:18 AM
Not about to try at this stage but it interests me how you create 9 - 18 ct gold - I understand there is a proportionate addition of copper or brass or something like that but that's about the extent of my knowledge (or lack thereof). Can anyone add to my education?
Title: Re: Moulding Gold
Post by: FlashGP on June 25, 2019, 06:10:15 PM
Hi Moth,

There are tables you can look up to give the ratios neede for the desired colour, yellow, rose, white (also the less common purple, green and black).  You would need ti get the quantities for 18ct and subtract them from 9ct to work out how much impurity to add to 1 oz of 18ct to make it 2 oz of 9ct.

If the percentages are the same, you could use gold alloying beads from AJS or A&E Metals to oncrease the dilution of the hold and turn 18ct into 9ct gold.  These beads are not gold, but an alloy which when added to pure gold makes the quantity of carat gold you want.  They usually also include deoxidising agents.