Flux/ Smelt Questions

[milprileb]

May I please ask this

I smelt wheel weights and they got grease on them and smoke , I can often toss a match onto them and it burns . I stir the molten wheel weights with a large stick and when the crud and metal clips are all afloat , I skim them off.

Now having said that, does this grease/oil that is smoking aid the fluxing of the metal or once I pull out the junk and metal clips, do I need to flux again ?

Secondly, I don't have access to sawdust but I have a lot of cob media that is too large for cleaning brass (came from pet store) and I use this as a flux but I sure don't pour molten metal about. I stir this cobb and its burning to ash and I stir a lot and then skim any impurity that surface on the melt.

Please comment on what I just said and let me know what you think. Am I missing something or going about this wrong or making bad assumptions?

Thank you

[Wayne Smith]

Nope, your assumptions are right on. As long as your melt is clean you are good to go. If you have excessive heat you will get a scum on top after a while. That is just the tin/lead oxidizing, fluxing will return you to a clean melt.

[lwknight]

You are exactly right.

[cbrick]

does this grease/oil that is smoking aid the fluxing of the metal or once I pull out the junk and metal clips, do I need to flux again ?

All depends on how clean you want your alloy. Yes, the grease & oil will serve as a flux, sorta. After I get all the clips and other lumps of whatever out of the pot I flux with sawdust stirring vigorously and skim off the ash & whatever may be in it. I then flux again with sawdust. I want my ingots as clean as I can get them, when I add an ingot to my casting pot I have confidence that it is as clean an alloy as is practicle.

Greases, oils & waxes will not reduce tin back into the melt but will remove some of the other impurities including the tin.


Secondly, I don't have access to sawdust but I have a lot of cob media that is too large for cleaning brass (came from pet store) and I use this as a flux but I sure don't pour molten metal about. I stir this cobb and its burning to ash and I stir a lot and then skim any impurity that surface on the melt.

I can't imagine not being able to find sawdust, its about as common as stink on poop. There must be a lumber yard, cabinet shop, Home Depot or some such place. Get some one gallon zip lock freezer bags and go to one of these places and fill up the bags. A few of these bags is enough to last a good while. Or if you prefer, Pat Marlin on this forum sells a hardwood sawdust that's pretty reasonable.

I have never used corn cob but I would think it should work, don't know why not. I have read of people using kittie litter and haven't tried that either, I have always thought that kittie litter was made from clay. This may form an air barrier on top of the melt but I can't see it being much of a flux.

Rick

[D Crockett]

Cbrick just to let youy know kitty litter is used as a barrier to keep the tin from oxidizing it's not as a flux here is a list of things I have used as a flusing agent --- a paint stir stick ,candle wax, used moter oil ,bees wax, pine tree sap, a hand full of oak leaves, bambo chop sticks , you can use anything that has a carbon base to it as a flux D Crockett

[milprileb]

Just a note on Marvelux. I got a big tub of it and what a mess it makes in my casting pot. While it smokes less than other flux options, this black gunk is terrible to get off innards of the pot.

This last casting blitz I ran 5 ten pound pots of lead thru my Saeco No.24 pot and used the corn cob as flux, Seemed to work fine (yeah it smokes) but it also seemed to take Marvelux crud out of the pot.

I am using a split 2x4 to stir the melt in a dutch oven when I smelt WW. I trust this is adequate for the purpose unless anyone had a better stirring tool. How long do you all stir by the way?

[Jim Flinchbaugh]

Isn't the stir stick enough of a flux if you get it charred good?

[geargnasher]

Isn't the stir stick enough of a flux if you get it charred good?

For already mostly clean alloy with just a little oxide scum on top (as in a casting pot) it usually is. For a smelt done with filthy wheel weights or similar, a round with the sawdust after initial skimming is a good idea, because it acually FLUXES the melt by removing contaminants from the mix that aren't removable by simply adding a reducant like wax or oil and skimming.

Grease, wax, and oil DO reduce oxides back to elemental metals very well, and DO NOT remove tin (that's what borate fluxes do, and that's why I detest them), but the grease/wax/oil doesn't remove the other mixed-in elemental junk that are contaminants to boolit casters like sawdust does. Grease/oil/wax is a good reducant, but poor flux. Sawdust does both.

I find the dog pee residue found on most WW to be a good reducant, as is tobacco juice and blobs of tire mounting lube. :kidding:

Gear

[firefly1957]

Tire mounting lube is sometimes sulfuric acid! Just to let you know I am not sure which one you are using. I have also used bar soap as flux it is best to keep shim to a minimum and I no longer use it going with wax instead.

[Wayne Smith]

Isn't the stir stick enough of a flux if you get it charred good?

I ladle cast from an iron pot on a gas burner. When I run the pot hot for some molds the oxidation happens fast enough that a stick is not adequate. Some old candle wax is easily sat hand and does a good job reducing the accumulation of oxides.