"Fluxing" questions

[Mike W1]

Couldn't guess just which section this ought to be in, please move it elsewhere if need be.

At age 73, with a couple thousand ingots on hand, I'm probably not gonna process a lot more lead but wonder about a couple things. Used to use candle's for "smelting" then switched to Stearine bars that we used to get at the Telco I spliced cable for.

After reading Mr. Fryxell's chapter on fluxes and guessing he might be on this forum I wonder how that stearine would fit in chemically? The little metal I now accumulate probably doesn't justify learning how to use sawdust correctly and I don't think I really want any of it in my Lee 10#'s.

Current casting procedure I use is to feed my feeder pot with ingots and sprues fluxing it with NEI's flux which I think is rosin of some sort. Then feed the lower pot hot metal into which I stir a pea sized piece of bees wax if the surface loses it's shine. Not every pot full by any means. Seems to work so far.

Am wondering where the stearine and NEI's flux fit in as either reducer agents or fluxes.

 

[Ian]

Stearine is a tryglyceride derived from beef tallow. It's a sacrificial reducant, same as NEI's rosin. So they both fit into the reducant category, not the adsorbent flux category occupied by woods and borates.

 

[Mike W1]

Well then I guess I can use flakes of that if I ever run out of NEI flux. It's my understanding that bees wax also falls under the reducant category also?

 

[Rick]

That's correct Mike. Various waxes and oils will reduce oxides & return them back into the melt (but not clean the alloy). The borax will also but it is also a flux and will remove (not reduce) the oxides including your Sn and Sb not to mention how horribly nasty messy it is to use. The borax flux isn't allowed in my shop.
.

 

[Ian]

Grease/wax/oil/fat or essentially anything that makes fire on top of lead will act in some fashion as a "sacrificial" reducant.

Anything that supports a reduction-oxidation reaction, where oxygen is given up by one substance and transferred to another, will turn oxidized bullet metal into elemental bullet metal, such as turning lead ( or tin, antimony, etc.) oxide into free lead while at the same time turning a blob of hydrocarbon wax into carbon dioxide, soot, water vapor, light, and heat.

As Rick explained, some things are to bullet metal fluxes, some are reducants, some are both. Wood is an example of something that first reduces through the combustion process, then fluxes by producing adsorbent carbon which binds with oxides of things not reduced by the redox reaction such as oxides of zinc, iron, and aluminum. The adsorbed contaminants can then be skimmed away with the ash. Simple hydrocarbon reducants aren't efficient fluxes because most of their physical presence on the melt's surface is eliminated by burning.

 

[Brad]

Maybe Glen can chime in here but I think burning the flux, in my case wood shavings, helps the process. Low order combustion gives off a fair bit of carbon monoxide which happens to be a pretty darn good reducing agent.

It is the ability to adsorb things we don't want that separates the fluxing and reducing properties of wood from the reducing properties of wax.

 

[RicinYakima]

The other issue with borax is that one of the products of combustion is HCl; that combines with water in the air and makes hydrochloric acid. That is what causes the rust issue with borax products.

 

[Rick]

Yep, the borax is incredibly hydroscopic. Even things like your stirring spoon caked with it will suck water right out of the air making for some exciting times when placed under the surface of the melt. Everything that comes in contact with it will gunked up, the inside of the pot will become so packed with it that a stiff wire brush and drill motor is needed to grind it out. One of the happiest days of my casting life was the day I threw that crappolla in the trash. One of the first things I noticed when I started using sawdust was how incredibly clean my pot was and that it stayed that way.
.

 

[Brad]

I did the Marvelux thing for a bit. I don't miss it. The mess, the goo, and the spitting as I place my stir spoon in the pot. It does a great job of cling to everything in the melt. Sadly that includes the pot and the stirring device. It also removes the oxides rather than getting them back into the melt.

Couldn't pay me to use that stuff again.

 

[Maven]

If I didn't have to cast indoors, sawdust would be my first choice as well, but indoors it's Marvelux. The hygroscopic nature of it is a PITA, but resting the stirring spoon on the molten metal to dry it works with nary a problem (don't ask....). Btw, I don't get much Marvelux residue in my furnace either and no collateral rusting at all. Sawdust? I wish!

 

[Rick]

I would quit casting before I would bring a container of that into my shop. Get me started on Marvacrap and I may have to tell how I really feel about it. I did use it for several years and unbeknownst to me I was sucking all the bar tin right out of my alloy, depleting the Sb not to mention the gunk, the mess, the rust, the water.

If you going to use it yes, there is no choice but to heat anything going into the pot sufficiently to drive ALL moisture.
.

 

[62chevy]

Rick nailed it with sawdust and a clean pot

 

[300BLK]

Back when I purchased flux from NEI, it was carnauba wax flakes. These days I am generally using some of my less successful bullet lubes which were mostly beeswax based.

I found beeswax preferable to candles or paraffin (for fluxing) due to its higher flash point. When casting bullets, I'm indoors and under my hood with exhaust fan. I smelt outdoors only with a propane fired burner and 5 quart dutch oven.

 

[Rick]

Don't confuse the terms fluxing and reducing.

Fluxing will clean the alloy and reduce Sn and Sb oxides back elemental metal plus leave an oxygen barrier if left on top of the melt.

A reductant will reduce Sn and Sb oxides back elemental metal plus leave an oxygen barrier if left on top of the melt. Clean (flux) the alloy will not.

Wax and oils are a reductant. Such things as sawdust are a flux in the carbon that is formed as it burns and will "flux" (clean) the alloy.
.

 

[Mike W1]

Well as long as this topic appears to be alive, what is the actual procedure using the saw dust? I'd assume to do any good you have to get it into the melt and stir the heck out of it. And is just the somewhat vigorous stirring gonna get it into the metal at the bottom, or am I missing something here? Sawdust is pretty light weight compared to lead.

 

[S Mac]

I'm sort of a novice myself but I thought ladleing the alloy thru the floating sawdust was the method, what I do anyway.

 

[Brad]

I will tell you what I do.

Once the lead is fully molten and close to final temp I place enough wood shaving to cover the melt. I want enough to cover the pot maybe 1/4 deep. I want the shaving to dry so for maybe 15-30 seconds I use a spoon to lift molten lead from the pot and pour it over the shavings. Why do this? Because even dry wood can have enough moisture to give bad reactions if pushed under the surface. I then use the spoon to push the shaving maybe 1" under the surface and also make sure any oxide film is pushed under too. By now the shavings are smoking heavily. I light the shavings on fire and keep mixing them into the melt. Once the flames stop I can really stir. I use a stirring motion that creates a vortex wishing the pot at a slight angle. Think of beating eggs but in a deep pot with many dozens of eggs. I do this to brings any grunge to the surface. I then skim the ashes and what not off the surface. I will often stir more after the melt surface is skimmed to make sure I won't have suspended materials. Rarely do I find more.

I now ladle cast exclusively so I have no fears of ash plugging the pour spout.

 

[Rick]

Really brad? Well, if it's working for you I guess you should do it that way.

For me I wouldn't do anything to push it under the surface. While it's true the ash is much lighter than lead and logic would say it will float to the surface but I wouldn't bet a cup of coffee on that. Lead is easily dense enough to hold at least some of it in suspension. That's the same reason I would never stir the melt with anything made of wood. It's become popular of late to use paint can stir sticks to stir the melt. Common sense should tell you that the stick will char under the melt, rubbing the sides and bottom of the pot WILL break off pieces of charred wood and again, the lead is dense enough to hold those pieces in suspension. Whatever is held there will end up in your bottom pour spout and in your bullets.

Proper fluxing isn't all that quick. Proper fluxing is using a spoon or ladle to bring up alloy from deep in the pot and pouring it through the sawdust and sawdust ash. It must be done long enough to be reasonably assured of cleaning the alloy in the pot. Putting some magic "flux" on top and giving it a quick stir with a magic stick isn't going to accomplish the goal of cleaning the alloy.
.

 

[Brad]

Like I said, I stir in a manner that brings melt from the bottom to the top. This up current brings suspended material to the surface where it can be removed. I can stir like the dickens later on and I don't find bits of ash anywhere.
It isn't a quick process. Can't be overdone either. Stirring is critical in my opinion.

It hasn't been mentioned here and isn't really "fluxing" per se but I do keep a small black of paraffin by the pot. After a while I find the stream from the spout of the ladle gets some oxide buildup and the flows isn't as focused. A small application of paraffin to the spout clears this right up.

 

[Mike W1]

I gonna keep some notes on you guys' comments and probably talk myself into trying it!