What's your favorite Flux?

Cityboy,

Just FYI, the very best flux I've ever used is sodium hydroxide, or ordinary lye.  It seems to actually reduce the slag oxides back to metal!  But it is NOT one I'd recommend for the average caster:  Lye is VERY dangerous!  It'll eat the skin (and underlying flesh) off of any contacted area quickly, even at room temperature.  You can imagine what it will be like at 600+ degrees.  It is also very hydroscopic, and will absorb water from the air very quickly.  Adding it to a hot melt is just asking for a steam explosion that will throw hot lye all over you and the rest of the room.  Not a good thing.

However, it is not without it's uses if you take these hazards into account.  I was once given a barrel of linotype slag from a print shop.  I recovered it quite nicely by placing some lye and the slag in a cold pot and allowing it to heat together.  The heat drove off the water long before any alloy melted.  Once the pot was up to temperature, the amount of alloy I recovered was phenomenal!  I then poured it into ingots in a normal manner.  When done, I rinsed EVERYTHING with vinegar to neutralize any remaining lye.  If anyone decides to give this a try despite these warnings, be bloody sure you have protective gloves, and a face mask and rubber apron at the very least!  I'd also recommend doing it outdoors, with a good fan to keep any vapors (actually, aerosol particles) away from you.  Notice:  You'll be the only one who is controlling what you do, or how you do it.  You will also be the only one responsible for the results!

I REALLY like the idea of using Ivory soap for a flux.  The main thing fluxing does is wet out metal oxides to release entrained alloy, and what would be better wetting than a soap?  I wouldn't have predicted the lack of residue and smoke you report,  but that's all to the better.  Gotta try this:  It's one of those “Duh!  Why didn't Ithink of that?” ideas.  Thanks!

A couple of other thoughts:  The slag on the top of the melt is mostly good alloy that is sorta mixed up in some metal alloy oxides.  You don't need to flux nearly as often if you don't form so much oxides.  And a good way to prevent forming the oxides is to keep air away from the melt.  (Personally, I think this is mostly what sawdust, etc does.)  I've had pretty good luck by cutting a thin steel disc to fit the top of the melt, with a cutout for the pour release rod of course.  Thread or weld an old machine screw to the center to make it easy to pick up with a pair of pliers if you want to add an ingot or two.  Once the melt is liquid, just set it on top. It'll keep the air away from the hot melt very nicely.  You'd be surprised at the difference it makes, particularly with something that needs a high temperature to pour well.

The other thought is that although the lid approach works, I find it more convenient to simply do away with the fluxing almost entirely:  Just scrape the slag off the top of the melt (I use an old, long handled spoon with a bunch of small holes drilled in it:  Sorta like a collander.) and knock it into an old soup can.  When you have a couple of can's full, run an extention cord OUTSIDE to power your pot, and fill it with your slag scrapings from the last year or so.  Heat, melt and flux THEN, and get a few ingots to go into your next batch of alloy.  This avoids all the smoke and odor, not to mention providing a dramatic improvement in domestic tranquility by avoiding annoying the wife too!

Molly