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Casting Metals Management


#1

Hi All,

I have been sending my casting out for years. Soon, I will be doing it in house again. As I recall the rule of thumb for mixing sprues and buttons with new gold is 50/50. Is that still the case? Does it apply for all golds and sterling? Is pickling and ultrasonic cleaning of the sprues and butttons enough to remove all investment and flux? I’ll be using Prestige Optima for investing. In the past I used boric acid powder for a melting flux. Is it still the flux to use.

Thanks,

Gene


#2

Hi Gene

You are allowed only one cast with silver!!! Jo Heimer (spelling?) shares my thoughts. Cast with Silver only once and get it refined. If not, you will have multiple pin-holes almost everywhere. I had over 525 grams of silver for a new casting, I decided to give him ‘clean silver’ instead and we all were happy with the next casting results.

***Gerry Lewy ***

Toronto.


#3

Hi Gerry,
That’s helpful. I never did much silver casting in the past. But all new silver for each casting is something I didn’t know. Seems to me that it’s different for yellow and white gold. Am I correct that 50/50 is the rule of thumb.
Thanks,
Gene


#4

If you are just going to dump metals together and cast then yes, 50/50 is the way to go.


#5

Are we talking lost wax investment casting or casting ingots and basically re-manufacturing the silver. I heat the ingot mold to get the moisture out and then put it into my burnout oven at 300C. I melt my scrap adding new as needed to get to the amount that I need to make the ingot. Add a little borax and stir with a graphite rod. Once the melt is ready, I get the mold out of the kiln (hopefully without burning half my middle finger like I did last week), pass a propane flame without O2 over the mold, assemble the mold, remelt the silver, pour, remove the ingot and then prepare the ingot. I prepare the ingot by sanding off all of the flashing down to clean metal. Then I forge it in two different directions, anneal and then roll, forge, draw or whatever to get to the shape that I need annealing on a regular basis. I don’t have pin holes or porosity and it works just like silver off the roll from Hoover and Strong even though some of it may have been through this process a number of times. I only do this when I need a piece of stock that I don’t have new from the refinery, but I am very comfortable using it when prepared this way. I am not a metallurgist, so I don’t know what is right or wrong, I just know what works for me. Regarding maintaining a .925 content, I try to add enough fine silver to compensate for any solder that might be in the scrap, however, in preparing the scrap I cut out all the solder that I can find and then run a magnet over the scrap. Comments please because I would not want to lead someone in the wrong direction. Thanks…Rob