Bad Days Happen

Yesterday was a bad day. I picked up castings from my local caster and a few had major problems. 

One ring lost it's stone during casting. This one had a beautiful marquise shaped sapphire set directly into the wax. Apparently it fell out during the casting process and never was seen again. Now it will be a real challenge to hand set another similar stone in the impression. Marquise shapes are so tough to set flush into the metal. They break really easy and its hard to get the fit right.

Another ring with a beautiful black diamond was at least fixable. Some silver covered the surface of the diamond, hiding the black beauty underneath. Thankfully silver is so much softer than a diamond, so the silver can be carefully polished away without scratching the diamond. 

But the real bummer was the casting of a rough diamond stacking ring. A quarter of the silver ring is totally messed up. It is porous and has pits all over. Something that can not be fixed. I will have to redo this again. Hopefully I get all the diamonds out of this screwed up ring. The really bad thing is that last week 2 more people ordered those raw diamond rings and one even has to be done in 18 karat gold.  Now I am rally terrified that all those 5 rings will go wrong when I try it again next week. If all goes well it should come out like this ring did. 

It is always a challenge using this method. I had some rings come out great and some others were ready for the scrap bin. It seems to be a 50/50 chance. I really wish I could afford my own casting setup to be able to experiment with this more. Unfortunately this equipment is really expensive and needs a large ventilated space. It also eats a lot of energy, so for my low production runs it would be not very sustainable.

The stone in place casting method allows to create some settings that would be almost impossible to get otherwise using the hand set method after the casting is done. Stone-in-place casting dramatically reduces labor costs associated with manually setting tiny gems.

In stone-in-place casting, a wax model of the jewelry piece is created, and the stones are set into the wax prior to casting. The wax model is placed into a flask and a fine-grained, heat-resistant plaster called "investment" is poured around it. Once the plaster has set, the flask is placed into an oven and heated until the wax burns off, leaving behind an empty cavity and the stones, which are held in place in the cavity by the investment. The burn out timing has to be adjusted slightly when stones are in the casting. The temperature changes have to be more gradually as temperature shocks can damage even the hardest stones.

The jewelry metal — normally gold or silver, since platinum's melting temperature is higher than most stones can tolerate — is melted and poured into the cavity, filling the space left by the wax. After the flask cools, an almost finished, stone-set jewelry piece is removed from the investment. Once the sprue is cut off and metal is smoothened, it just needs to be polished.
There are still limitations to what can be done with stone-in-place casting. For example, only certain stones can be used in this technique. Since the melting temperature of gold is 1,700 F to 1,800 F (927 C to 982 C), stones must be able to tolerate fairly high temperatures. Stones that change color when exposed to high temperatures, such as amethyst or blue topaz, or which will burn at these temperatures, such as pearl and turquoise, are not suitable for stone-in-place casting. The most popular choices, unsurprisingly, are diamonds, ruby and sapphire and synthetic stones, which are durable stones with a high tolerance for heat.

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