Fluxing with sawdust, tell me how.

[Murphy]

Okay, it's time for some change in my decades old method of fluxing my alloy.

I've always used a form of wax, bullet lube or Marvelux. I'm done with Marvelux, corrosive and nasty. Don't think so? Try tossing the dross from a fluxed pot using Marvelux and toss it in a metal coffee can, you'll soon see.

Gathering sawdust won't be any issue, plenty of local lumber mills. Is it as simple as just tossing a good handful into my smelting pot and fluxing as usual? Once all the metal clips have floated to the top I remove them with a slotted metal spoon. Then I begin scrapping the sides and bottom, removing every little bit of impurities I can. Once I'm at that point and its time to flux, now what?

Once I have my ingots cleaned and its time to cast, what method using sawdust do I use? The same as usual and leave the burned dust on top of the melt?

This is why I joined castboolits. A person can cast for decades and still learn new things. And it is time for something new.

Thanks,

Murphy

[docone31]

I use Kitty Litter rather than sawdust. For me, on cold days, it acts as an insulating layer and helps keep the melt hot.
With sawdust, I just sprinkle some on top. Then when warm, I stir. It gathers impurities to it and floats to the top. The carbon layer keeps oxidation down.
I am not so sure sawdust is a flux, or a barrier.
I know it does work well. As it burns down, it floats and gathers crud with it.
I use vegetable oil as a flux. I get some shiney clean melts with it. Again, I do not know if it is a flux either, or rather a barrier and deoxidant.

[smokemjoe]

I have used them all, I still like to use beeswax for flux and kitty litter, the kitty litter I just used the large pieces, I use a strainer to get all the small pieces out, Have found them on the sides of the bullets using my bottom pour pot. Joe

[clodhopper]

My understanding of flux is that flux provides carbon for oxygen in lead oxides to bond with under heat. Impurities will come to the top with agitation. Lead oxides willl not form when carbon is present when the lead is stirred.

I live in a dry climate, so I have no trouble keeping sawdust dry.

I tried the kitty litter thing. Yah, it provides a barrier but the barrier requires mantience when ever you add lead to the pot.

Bottem line for me is kitty litter is cheap, sawdust is free.

The parrifin, beeswax, and bullet lubes all make breathing wheezy.

For me sawdust is the perfect flux, free, smells better, works good.

[DeanWinchester]

I have to keep cedar shavings for the dog anyway, so I just use that. Cedar shavings smell awesome and aren't nearly as noxious as the other methods I've tried. I notice that my dross is much less using too. I'm not losing anywhere near the amount of nonlead goodies like tin. I ladle pour so I am constantly scooping off dross. I save it and render it back to usable lead later. Since taking up cedar shavings my bullets are harder too. Air cooled wheel weights, BTW.

[dRok]

I use cross cut shredded paper from my office and it works well. I will also dump in some used motor oil occasionally and light it up, its more fun than paper and will provide heat to melt a full pot faster...

[Bullshop]

I use pencil shavings from the pencil sharpener my kids use. Its mostly cedar and very fine texture. I add a small amount of boolit lube to it and light it to produce more heat at the surface and less smoke. About a tablespoon of pencil shavings and a split pea size bit of lube will clean up a 20 pound pot nicely.
I find the extra heat of burning at the surface especially helpfull when blending enrichment alloys containing a high percentage of antimony.

[Charlie Two Tracks]

Don't push your sawdust under the melt. It will bubble like crazy. I put mine on top and then light it with a torch. Once burned up, I use the ash to stir into the melt and leave it on top of the pot.

[shooting on a shoestring]

When my melt is very close to casting temperature, I cover the top with a handful of dry sawdust. That gives me about 0.5 to 1 inch layer of sawdust. I stir the pot well using a slat of hardwood until all the sawdust is charcoal, then skim the charcoal and dross. Then I dunk my ladel and grab a mould. I too keep the dross and reclaim it, and flux it well.

I do make sure my sawdust is dry. I really don't want moisture on my melt or worse, stirred under for a steam burp.

[merlin101]

I just toss a couple handfuls in a big pot (say aprox 100 lbs) and let it sit in the surface to make sure it's dry, then just as it's starting to glow I stir it in

[Bigslug]

I'm a long way from "Village Elder" status on these matters, but here's how I'm currently rolling:

The smelt of raw materials is done outside in an iron pot on a propane burner. The jackets, clips, and dirt get skimmed off first with a fry spider followed by a bent spoon, then a big handful of sawdust gets thrown on. Once it's hot, I light it on fire. Once it's done burning, I stir it in with the spider for a couple minutes, skim all THAT crud off, then ladle out to the ingot molds.

Actual casting gets done inside, so smoky sawdust is a no-go. The metals go into the bottom-pour pot, get mixed, crud skimmed off, and then covered with kitty litter as a heat insulator and oxygen barrier (we have cats, so not a real extra expense).

I figure after the first flux and the second skim-off (crud floats after all), the metal is "clean enough" and that extra fluxing might be pulling out useful stuff I want to keep (namely tin).

[geargnasher]

Murphy, there is a lot of misinformation given already here as to what exactly does what, so I'm going to try to clear it up for you with scientific facts confirmed with the experience of a whole bunch of us.

OK, here's the deal, as figured out a long time ago by a Ph, D. chemist named Glen Fryxell. There's three things we do with our dirty scrap alloy to process it: There's cleaning dirt out, there's reverting the oxide scum back into useable, elemental metal (called "reducing", the opposite chemical reaction to the process of "oxidizing", which is what makes the scum in the first place), and there's FLUXING, which is removing the dissolved metals we boolit casters consider impurities because they impede the flux, or "flow" of the metal when we try to cast things like boolits out of it.

To get the dirt out, it usually just requires a good scraping, stirring, and skimming because it will float to the top. Unless the dirt is denser than lead, like Uranium, but I haven't seen much of that in my boolit metal.

Then there's getting that tin-rich oxide scum to go back in rather than skimming it and tossing it. This is where the "reduction" of oxides takes place, and that requires only heat and unburned hydrocarbons. You can use wax, grease, oil, tallow, butter, margarine, tree bark, grass, sap, hair, ground coffee, cereal grains, rosin, vaseline, etc. You get the idea. The hydrocarbons react with oxidized metal to make carbon dioxide, water (vapor), and DE-oxidized boolit metal. There will be a tiny bit of ash unless you can make the reaction in your open pot stoichiometric, which you can't, and it doesn't matter. Just skim the pinch of grey powder and call it good.

Now, there's FLUXING. This is the part that is mostly misunderstood. A chunk of candle was DOES NOT constitute flux. Marvakrap does, but it has a lot of drawbacks, and it doesn't REDUCE OXIDES at all, neither does kitty litter. Kitty litter doesn't even flux, but I digress. Back to fluxing. Most lead scrap has all sorts of evil junk in it like calcium, iron, aluminum, zinc, cadmium, you name it. We want that stuff GONE but want to keep antimony, arsenic, copper, and tin, along with any trace gold, silver, or copper that might be in there. The thing that does it all is CARBOHYDRATES, and sawdust has plenty. Yes, you can flux with potato chips, if you don't mind the salt corroding things. But you said you hate the stuff I call Marvakrap, so that rules out salty snacks for flux.

Since Rosin and sap makes an excellent sacrificial reducant, and carbohydrates do too, sappy pine shavings make some of the very best flux/cleaner/reducant to be had anywhere at any price.

But in order to get the fullest effect you must expose as much of the metal to the smoldering sawdust as you can so it can soak up that nasty calcium, aluminum etc. etc. while also sitting on the top and keeping oxides reduced. Oxides float, and putting the sawdust on top takes care of reducing them back into the alloy, but to really get the bad junk out you have to expose all the metal in the pot to it. To do this when smelting, first I toss in some wax to reduce the oxides out of the clumpy, dirty junk floating on top after getting all the scrap melted and skim all that off. Then I put about an inch of chainsaw debitage on top (the bar oil residue helps some too) and let it start charring really good. Then I take my big ladle and scrape the heck out of the bottom and sides of the pot and get it stirred up good, then start bringing up big ladlefulls of alloy and drizzling it through the smoldering sawdust layer. I do this over and over again until the sawdust is just a grey ash, which I skim off and toss, then add another layer and repeat. If there is a lot of the junky metals in there, you will notice a big difference in the ash from the first fluxing to the second or third fluxing. The ash from the first fluxing will be more like burnt aluminum foil and later fluxing ash more like fine powder.

That's it! After cleaning, fluxing, and ingotizing, you may not need to flux any more. When casting, if you got the bad junk out during the smelt, all you need to do is keep the oxides reduced, if even that. Kitty litter is good for sealing the surface of the casting melt from oxygen on a bottom-pour setup or to insulate and keep heat in during cold-weather casting, but in and of itself does nothing to absorb impurities or reduce oxides. During casting, you can use wax to keep the oxide scum reduced, stir with a wooden stick, or do what I do and float about a quarter inch of sawdust on top of my casting pot, because as it burns to ash it seals the surface just like kitty litter does, only is easier to clean out and less dusty. The charring sawdust layer, while actively charring and before it turns to ash, is also a great reducant for the flash-oxide that forms on sprues, so if you toss them back in the pot as you cast it will help keep the excess scum caused by that process from forming. You might skim and refresh the sawdust periodically if you wish while casting. Otherwise, grease/wax/oil will keep the oxides at bay.

Hope that sheds a little light,

Gear

[Hardcast416taylor]

Well said Gear.Robert

[Murphy]

Thanks for all the information gentlemen.

As the old saying goes "Keep doing what you've always done, and you'll get exactly what you've always gotten".

I'll eventually get around to trying sawdust and get back with my experience.

Thanks again,

Murphy

[clodhopper]

Thanks geargnasher, your info did make sense. The burnt tin foil part, yeah I've scraped it off, never understanding the composition of the material.
The grey ash.
Good stuff, I need to read your post again!

[Nose Dive]

Gearnasher is dead on. Kitty litter is best used by the kitty. Need Carbon in the SMELT.. Sawdust is the best...Mix well. Scrap bottom and sides. I get range scrap..dirt, ****, cig buts, rocks, sticks..name it. Spread on driveway...water wash with hose...sit over night. Shovel up in AM..put in COLD POT..FILL IT UP...come up SLOW on smelt pot..slow...slow cook off any water...FLUX ...FLUX..>FLUX with saw dust...it offers the carbon needed... mix...scrap the dross... Do it three times with sawdust... Make ingots.... ..Now ready for alloying later... Kitty need to pee in litter..does nothing for smelt....

NEVER...NEVER ADD THE SCRAP TO A HOT POT OF SMELTED RANGE SCRAP. KAAABOOOMMMB! One pot of scrap at a time.

Read the stickies on this site about wet lead and smelt pots. I have smelted some Nasty Wet ****.... Slow..slow...slow... FLUX...FLUX...FLUX... don't get greedy and in a hurry....

Nose Dive.

Cheap, Fast, Good. Kindly pick two.

[fishnhunt]

Murphy,
I've been adding dry sawdust and a little paraffin and stirring - before the ww clips come out; I'd be interested in what geargnasher has to say about that and whether I've been doing it wrongo. It seems that it help the clips to shed lead and they are darker and just more "clean" I guess is the way to describe them.

[a.squibload]

That`s been my experience. I add sawdust before removing clips,
then again to skim dirt, sometimes a third time just for.
Good writeup by Gear.

[geargnasher]

Sawdust in with the clips works well too, they come out completely clean of lead, no drossy strings or clumps clinging to them. The only reason I use wax to clean the clips before skimming is that I recycle them and want my sawdust ash separate, plus I'm too lazy to shake all the sawdust off the clips as I skim them with a slotted spoon.

Gear

[Pb Burner]

Gear,
Great info, makes sense and most importantly, easy for a new boolit caster to understand. Your info and help in the past have been a huge help to me. Keep up the great posts!
Thanks, Burner