Flux this is difficult!

How's that for a subject line? nooB Ben back with another fundamental
question. I'm having consistent issues with picking up O2 in my sterling
casts and suspect I'm fluxing up. Dealing with small enough quantities that
I melt right on the flask in a cavity I create in the investment before
burnout then use steam method to force the metal down the sprue. Can't
afford a vacuum and furnace so suggestions to improve using assuming this
method are most appreciated.
I am not holding the oxygen rich blue part of the flame in the molten metal
and am sprinkling borax on it when molten. I remember now from threads a
while ago someone discussing "covering" in flux. How much flux should be
used on a 22gr button and at what stage(s), meaning
1.) melt, flux, cast....or
2.) melt, flux, re-heat to optimal, cast?
3.) Something else?
4.) Is borax vs something like Griffith Casting Flux my issue??
Thanks guys/gals, much appreciated.
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When you do your first melt, add borax. As the silver melts the borax should cover the entire surface of the silver from crucible side to side. You should see a glassy coating on top of the silver. The coating will get thicker at the edges because it will flow out to the crucible sides. There should also be a layer of molten borax under the silver as well. NO surface of the molten silver should be exposed to the air. Use a carbon arc gouging rod to stir the molten metal. While you are stirring the crap should come to the surface and be trapped in the flux. The borax is just regular old 20 Mule Team borax from the grocery store, just be sure you get borax and not their detergent instead. As for the steam casting, i'v never done it like that. I either used vac or a centrifugal caster. I would be doubtful that you will get good results using your mold as a crucible-too much chance of getting impurities in your mold and having the mold temp dropping while you are melting your silver. When you cast, your mold should be almost as hot as your silver so the silver does not cool before the mold completely fills all the details. If it does you will have incomplete castings as a result
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Thanks for the reply. I actually have the steam method down pretty well and haven't experienced incomplete castings since my second attempt (have about 2 dozen under my belt now). I don't think contamination or improper mold temps are the issue. I'm fairly certain it's gas that is.
The reason I stopped using the crucible was I was dealing with such small amounts and how fast the silver cools even right after a pour leaving you BARELY have enough time for steam before it freezes. I'm going to try using the same method with pure silver this weekend and see if I get the same tiny bubbles in the metal. If that happens with pure silver then we'll know it's not o2 that's the issue but it is in fact contamination right?
It's tough doing this on a budget. All the *proper* equipment will run $2500-$4000 easy: ace/ox tank, tips, burnout oven, vacuum, centri, tools, partridge, pear tree, etc.....I'm going minimal right now. I am told with practice, great results CAN be achieved using the basics....and when you look at some of TUTS wares, I gotta believe it's true =)
Thanks again and have a good evening,
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