fluxing with sawdust

[Oklahoma Rebel]

I flux with cedar sawdust as many others do, but I always end up with metal in the burned up sawdust when I skim. not sure but I am guessing my tin is separating?? I know it isn't antimony because it happened today with 20:1. if it was just some of the alloy it would be ok, it isn't a lot, but if it is my tin then it is a problem, because it is enough to effect the ratio of my alloy. please help and/or if anyone has recommended alternatives I'm all ears. thankyou, Travis

[Ola]

I always end up with metal in the burned up sawdust..

Metal in the ashes? Really? Do you let the sawdust burn completely? Do you light it up so it burns with flame?

I do that, and I don't think there is any metal in the ashes afterwards..

[nagantguy]

never noticed metal ash but I don't use saw dust any more cause I'd get so much thick black crud in the bottom and sides of my pot, might be the saw dust I uesd, a flaw in my technique but since I went back to a wax based Flux no more black sludge.

[dtknowles]

My sawdust flux burns to ashes. It sometimes has small silver dots mixed with the ash and even when it doesn't it still has a density much greater than plain ashes, it has dross or metal oxides mixed in. I save those ashes and mix them with even more flux and heat them in a pot and stir. I recover a fair amount of metal from the combination of the dross and ash. I have not tested the recovered metal for composition or hardness. It is at least mostly lead guessing from its apparent density, it could be higher in tin than my normal alloy which has only a couple percent tin to start with.

Tim

[runfiverun]

it's just some alloy.

[Oklahoma Rebel]

hey run, yeah dtknowles explained whats happening to me perfectly, its like the alloy is "sweating" up into the ash, forming into drops. I also have been saving the skim too, I melted some the other day and doing the drop test, it must have at least a fair amount of tin because it rings instead of a thud. it is frustrating though, because this hasn't always happened, when I was first starting it didn't happen. but I hadn't heard of using sawdust, I was I think using paraffin based boolit lube that I rejected. I think I should I try a mix of sawdust and lube, and if it still happens, then I will try just lube. im just not a fan of using paraffin, with the flare-ups, smoke and everthing. ok, well any more ideas let me know, next day or two I will try to get the lee 20 warmed up and try that, i'll let y'all know. have a good one, Travis

[runfiverun]

you need a fire or something else that creates an oxygen free barrier to return the oxides back into the alloy.
[it's a reductant not a flux]
this is where the wax comes into play.
when you burn different things they can release small amounts of carbon and all you need is some in the alloy to do the job.
I light wax off with a little strip of paper and stir everything in while the fire is going.
the ash is carbon and it is a flux but not a reductant it carbourizes the alloy which allows the different metals to bind together properly.
the carbon is a huge pain to get back out of the alloy though.

[triggerhappy243]

I seem to get quite a bit of "soot" residue in my pot as well. I do not sweat over it, I work around it. But it is good that OK Rebel sees this.

[dtknowles]

you need a fire or something else that creates an oxygen free barrier to return the oxides back into the alloy.
[it's a reductant not a flux]
this is where the wax comes into play.
when you burn different things they can release small amounts of carbon and all you need is some in the alloy to do the job.
I light wax off with a little strip of paper and stir everything in while the fire is going.
the ash is carbon and it is a flux but not a reductant it carbourizes the alloy which allows the different metals to bind together properly.
the carbon is a huge pain to get back out of the alloy though.

Once the Wood flux is burnt to ash it no longer has much free carbon, the carbon has been oxidized to CaCO3, CO2 and CO. The ash is mostly Calcium Carbonate with the CO2 and CO going into the air. There will be metal oxides in the ash with Fe2O3 being the most come but with Copper, Zinc and other metal oxides present as well. With wax flux you don't have much calcium or other non-HydroCarbon molecules so the flux helps pull those contaminates from the melt and reduces the Tin and Lead Oxides back to free metal.

Tim

[Oklahoma Rebel]

ok cool, ill do a little sawdust , let that burn down, then the wax, light it on fire, and stir. thanks!

[lightman]

I always saved candles and fluxed with them before I became a member here and learned about sawdust. I put enough on top of the melt to cover it and let it char completely and then stir it in really good. I even light it when it starts smoking. I'm not finding metal in mine like you describe.

[mold maker]

I have seen the tiny beads of metal, especially when working with really dirty lead or WWs. It doesn't amount to much weight wise.
Can't say I ever saw them when using wax or oil.

[Strtspdlx]

Get the melt hotter. The only thing that should stick to the dross is oxides that weren't reduced back in and dross. More heat helps carbonized the wood quicker allowing it to seperate instead of bond to and cool what you're trying to reduce.

[dtknowles]

Get the melt hotter. The only thing that should stick to the dross is oxides that weren't reduced back in and dross. More heat helps carbonized the wood quicker allowing it to seperate instead of bond to and cool what you're trying to reduce.

I think what is happening in my dross is when I flux it reduces oxides back to metal but these small beads of metal stay in the ash. Stirring will get most of them back into the melt.

Tim

[waksupi]

Go to kitty litter on top, and stir with a piece of dry dowel. Flux sitting on top of the melt does nothing. The stick gets to the bottom, and lets you scrub the sides.