jewellery manufacturing problems!

[shahravij]

Hi People,

This has been a really informative forum. I think this might not be the right place for the question, but I thought some one might be able to help me out here, especially if someone has experience with jewellery making.

We are facing problem with casting of gold jewellery of 14k. The gold loss is quite negligible when we cast 22k gold, but whenever we cast 14k gold, there is around 0.5% which is lost in the casting process. Does anyone know what could be the reason ?

Also, does anyone know a table with vacuum set up which can collect the gold flakes suspended in air in the gold jewellery manufactring workshop.

Thanks in advance,
Ravi

 

[butcher]

can I guess at this quiz ?

My guess as to the 0.5% loss in lower karat casting, base metals (oxidation) if all other fators are the same. (??)

 

[nickvc]

I think Butcher is spot on.
You will find that the assay will creep up when melting metals due to burn off of the base metals, you might find that as your used to casting 22 k that your casting your 14 k too hot and this will burn more base metals off. One of the large casting houses here in the UK make their own 9 k grain and always alloy at 374 as the casting process increases the assay to 375+ which here is needed or the item will not pass the Hallmarking rules.

 

[Dr. Poe]

Butcher is most likely right, however I've crushed and panned used investments in the past by very experienced jewelers and have gotten up to a gram of gold. That is caused by not completely removing all air from the investment in the lost wax process. Instead of using vacuum or vibration, try using both simultaneously. If you are producing any smoke when you melt, your zinc or copper is being vaporized. Dr. Poe :roll: