flux magic

[bigted]

ok been casting for awhile and i do flux with my lube...[small pee size ball every time i cast]...but ive always wondered what is the thing that happens when i drop that ball of lube onto the melt. it smokes and turns the top black immediately and i stir it in for around 5 minutes before starting to cast. seems to make the melt pour better or i imagine it to do so anyway.

question is this.......what exactly happens to the melt when a person flux's the pot...and why do i have to do so every time i cast boolits? been wondering this for a couple years...keep doing it but really would like to know what in tarnation happens when this small ball of lube gets mixed with my melt?

[montana_charlie]

http://www.lasc.us/FryxellFluxing.htm

[geargnasher]

You asked!

First, there are two things we want to do to our alloy once it's molten, REDUCE it, and FLUX it.

Chemical REDUCTION is the opposite reacton to oxidation, so all that grey oxide scum from the surface of your ingots that floats on top of the melt is oxides of the metals in your melt, and it's usually richer in tin content than anything else because a) tin oxidizes faster than lead or antimony when in a molten solution, and b) because tin oxidizes on the surface of the metal when it is molten, so that surface oxide on your ingots and boolits/sprues you remelt is rich in tin also.

FLUXING is the act of removing things we consider (as boolit casters) to be contaminants. We want to rid ourselves of calcium, aluminum, iron, etc. because things like that affect casting quality in a negative way.

To REDUCE the oxides to elemental metal, we need to introduce a "sacrificial" substance that will donate hydrocarbons, which turn metal oxides into elemental metal and combine the oxygen with the hydrocarbons to create carbon dioxide gas. This is where boolit lubes, or any grease/wax/oil will turn that oxide scum back into shiny metal. The part you don't see is the release of small amounts of CO and CO2 from the melt's surface as the reduction/oxidation reaction takes place. It's best to light the wax because that consumes extra oxygen from the metal and gives more active oxidation (combustion) to the reaction, which in turn boosts the reduction of the oxides considerably.

FLUXING is done with many things, but NONE of them come close to the effectiveness of plain sawdust, or rosin-rich wood shavings/chips like Pat Marlin's California Flake Flux. Any of the borate fluxes are worthless IMO because they remove tin from the alloy and don't reduce oxides at all.

Sawdust is also an excellent sacrificial reducant, to in effect it is the best single substance you could flux with, combined with stirring/scraping the sides of the pot with a dry wood stick, which forces the sacrificial reducant (wood) under the melt to get at any trapped oxides beneath. Be sure and scrape the bottom of the pot with something metal, like a long-handled teaspoon, and NOT your stick, because the stick sloughs ash off underneath the melt where it can get trapped and migrate to the spout, where you get little pits and inclusions in the surface of your boolits.

For an excellent article on this, read Glen Fryxell's "The simple act of fluxing" on the LASC dot US site.

So there you have it!

Gear

[geargnasher]

CM has the link I was talking about.

Gear

[bigted]

very interesting article charlie...thanks for the link and ive saved it for more future parusal as time allows.

[bigted]

i understand these points and if i were to bottom pour it prolly would be better for the flux...however i dip and seems like the sawdust would become trapped inside my ladle when dipping melt.

i do understand better now what happens with my lube ball in the melt. makes sense that it returns the needed tin to the melted state where i can and do dip it out for boolit making.

thanks again for the explanation and if others want to chime in id gladly read your comments as well.

[geargnasher]

If you dipper pour you have a couple of choices, either skim the ashes off (after working them into a pile against the side of the pot and squeezing out the droplets of captured, reduced alloy) or just leave it alone. The ash on top of the lead will stay so, and you can just keep your ladle floating in the mess. What comes out the bottom of the ladle will be clean, and that's what matters.

Ladling introduces a tremendous amount of the alloy to air over and over again, so it's nice to have a constant reducing action going on there, and an oxide-barrier of ash/charcoal floating on top. Lots of folks just stir and scrape with a stick and get to casting.

Gear

[cbrick]

bigted, here is some more reading, chapter 4 is on your question of fluxing but I highly recommend reading the entire book. It is by the same author as the mentioned artice but explained here in better detail.

From Ingot To Target (http://www.lasc.us/Fryxell_Book_textonly2.pdf)

Rick

[Bret4207]

You asked!

Be sure and scrape the bottom of the pot with something metal, like a long-handled teaspoon, and NOT your stick, because the stick sloughs ash off underneath the melt where it can get trapped and migrate to the spout, where you get little pits and inclusions in the surface of your boolits.


Gear

One of the many benefits of going from a cast iron pot to a stainless pot was the interior finish. My stainless pot is even smoother than my SAECO pot. I had never considered you theory of ash getting trapped beneath the melt, but then I'm pretty aggressive in my stirring and ladling. I'll have to give some added observation to that possibility accounting for some of the flecks I get in the melt.

[geargnasher]

Bret, I bottom-pour just about everything, so the ash IS a problem for me if I'm not careful, but since you ladle, it really doesn't matter at all if anything gets stuck on the bottom or trapped under the melt. One of the advantages of the ladle!

Gear

[303Guy]

You know, gear, you are a very knowledgeable man! I enjoy the way you observe and interpret. You have a whole lot to contribute to us all on these forums. Thank you.:drinks:

[Inkman]

You asked!

First, there are two things we want to do to our alloy once it's molten, REDUCE it, and FLUX it.

Chemical REDUCTION is the opposite reacton to oxidation, so all that grey oxide scum from the surface of your ingots that floats on top of the melt is oxides of the metals in your melt, and it's usually richer in tin content than anything else because a) tin oxidizes faster than lead or antimony when in a molten solution, and b) because tin oxidizes on the surface of the metal when it is molten, so that surface oxide on your ingots and boolits/sprues you remelt is rich in tin also.

FLUXING is the act of removing things we consider (as boolit casters) to be contaminants. We want to rid ourselves of calcium, aluminum, iron, etc. because things like that affect casting quality in a negative way.

To REDUCE the oxides to elemental metal, we need to introduce a "sacrificial" substance that will donate hydrocarbons, which turn metal oxides into elemental metal and combine the oxygen with the hydrocarbons to create carbon dioxide gas. This is where boolit lubes, or any grease/wax/oil will turn that oxide scum back into shiny metal. The part you don't see is the release of small amounts of CO and CO2 from the melt's surface as the reduction/oxidation reaction takes place. It's best to light the wax because that consumes extra oxygen from the metal and gives more active oxidation (combustion) to the reaction, which in turn boosts the reduction of the oxides considerably.

FLUXING is done with many things, but NONE of them come close to the effectiveness of plain sawdust, or rosin-rich wood shavings/chips like Pat Marlin's California Flake Flux. Any of the borate fluxes are worthless IMO because they remove tin from the alloy and don't reduce oxides at all.

Sawdust is also an excellent sacrificial reducant, to in effect it is the best single substance you could flux with, combined with stirring/scraping the sides of the pot with a dry wood stick, which forces the sacrificial reducant (wood) under the melt to get at any trapped oxides beneath. Be sure and scrape the bottom of the pot with something metal, like a long-handled teaspoon, and NOT your stick, because the stick sloughs ash off underneath the melt where it can get trapped and migrate to the spout, where you get little pits and inclusions in the surface of your boolits.

For an excellent article on this, read Glen Fryxell's "The simple act of fluxing" on the LASC dot US site.

So there you have it!

Gear

Thanks for that. I'm going to need to read it a few times before it sinks in, but very nice and simple explanation for NOOBS like me.

Al

[Bret4207]

FWIW, I used the waxes and oils for years and contended with the smoke and flame and not so clean metal. The guys here turned me onto stirring with a dry wood stick. I've given up the other stuff for the stick, except when reducing large batches of WW to ingots, at which time I use a lot of sawdust chips. I know Pat sells aromatic chips folks like and others have their own favorites. Myself, when I went to a stainless pot my dross dropped by half at least. I can see the diff between my stainless ladle pot and my ferrous steel SAECO BP pot. While Gear warns against it I don't use anything but the stick and stir and scrape through the casting cycle and the stick scorches away during the stirring and scraping. I can;t help but wonder if individual style of stirring and scraping puts a lot more carbon under the melt for some than others, seems logical. I have a hard time getting sawdust under the melt, or the ash it produces.

Now on the idea of an air barrier of BP, yeah, I can see the sawdust working great for that.

[Three44s]

I'll take Gear's admonishment about wooden stick stirring under advisement ........... other than that, I'm all go for throttle up on the rest of his info!

I like sawdust and a wooden stick.

Then I'll keep using my metal spoon to get everything to the top like I've always done.

It seems to me that as light as carbon particles are and as heavy as lead is .......... that a modecum of metal spoon stirring should get the soot out. I scrape the sides of the pot and carefully envelope some air into the lead and restir. If the carbon from the stick is hanging around in the melt .... to me it seems that it's stuck on something that needs to come out as well. More metal spoon agitation is in order.

Since I've gone "wooden" .......... my casting sessions have gotten much more productive (ie. far less rejects) so the proof for me is there.

Best regards

Three 44s

[geargnasher]

Lordy how I struggle to be understood sometimes [smilie=b: Lemme try again:

I never said it wasn't a good idea to stir with a stick and scrape the sides of the pot with it. I use a stick too for most of my pot work, in fact I have several stuck into a coffee can behind the bottom-pour. I prefer little 3/8"x3/4" maple "ricks" that are edge trimmings from my friend's cabinet shop. The hard maple is moisture-resistant and has no sap in it to pop or sputter.

The problem I found is when I scratched around hard on the bottom and bottom corners of the pot with my stick, THAT'S when ashes get sloughed off the tip of the stick and trapped under the melt. Not IN the melt, UNDER it. Don't get wild with trying to scrape the bottom of your bottom-pour with your stick and everything else will float to the top. If you need to scrape the bottom of the pot really well, use a spoon. If you ladle-cast you'll likely never know if anything is trapped under the melt, because it stays there and hurts nothing.

Gear

[cbrick]

I concur Three 44s,

I use a slotted stainless spoon and sawdust. I stir in a manor to continually bring as much alloy to the surface and in contact with the burning/burnt sawdust as practicle. I have never tried to get the sawdust under the melt but rather bring as much alloy up to the flux as I can.

I've yet to use a wood stick to stir though with as much as I've read here about it I did pick up a handfull of paint stir sticks at the Home Depot a while back. I'll try that one of these days but I'm skepticle that I would end up with alloy any cleaner than I have now. Who knows, maybe an old dog will learn another trick. Skepticle because it seems so logical that a charing stick under the melt will add junk into the alloy even if you don't scrape the bottom of the pot. I'll try it one of these days but . . .

Rick

[Three44s]

cbrick,

I think we are on the same page now that Gear clarified he's using the stick on the sides of his pot.

I would try a stick for sides but be careful and heat it up first ..... you'd be surprised how much moisture is in "dry" wood.

The relatively blunt nose of a spoon makes the best "bottom scraper".

The stick forces some carbon to be shed in the middle of the melt.

My experience with the saw dust is it stays on the surface and is only dragged down a little ways into the melt.

Hence the stick.

Thank you Gear,

I never really thought about the bottom and the stick but my spoon must have been getting me by but then, I just never really went crazy on the bottom with my sticks as that pointy nose just did not seem to cut much slack anyways.

Learn something new every day!

Best regards

Mark

[Mal Paso]

The way steel pops to the top of molten lead I never thought anything but lead would be on the bottom. I emptied my 20# Lee bottom pour to put in a thermocouple and found the bottom Covered with crud. Surface tension? I now know where my inclusions came from. [smilie=b:

[geargnasher]

That's right, Mal Paso, ash, dross, oxides, etc will get trapped under the melt due to surfact tension. Most anything inside the alloy "bubble" will float to the top and get worked out as you stir and skim, but stuff on the bottom won't penetrate the surface for the lead to rise up. Stuff trapped on the bottom WILL migrate to the spout on a bottom-pour and make those ugly little pits visible in the surface of your boolits.

Another big contributor to the dross inclusions in boolits is due to adding sprues/culls back to the pot as you cast. I did it for years until recently I did one of my routine empty/clean routines on my pot, and started getting inclusions about halfway through the session! Impossible, I thought, there's nothing down there but a clean pot and clean lead, and I didn't force any ashes down there. Well, turns out, it was the oxide on the sprues and cull boolits I was throwing back in. The solid, cooler lead sinks straight to the bottom and carries the oxide layer with it, and when the boolit/sprue melts, the little skin of oxide gets stuck to the bottom since it doesn't melt at casting temperatures. Since then, I run the pot down to about 1/4 full, add back all my sprues and culls, flux and skim, then add preheated ingots, scrape the bottom and up the sides with a spoon, reflux the top while stirring with my stick.

Since I started doing that, I haven't had to clean my pot once, and the inclusions went away.

Gear

[olafhardt]

I just started using a wooden stick and it makes a world of difference in my Lee 4 lb pot

[GRid.1569]

You know, gear, you are a very knowledgeable man! I enjoy the way you observe and interpret. You have a whole lot to contribute to us all on these forums. Thank you.:drinks:

I agree fully....

Indeed there are many contributors that give good guidance and have helped my understanding of the silver stream... they all deserve thanks...

[MikeS]

While I use a stick to stir the melt, and scrape the sides of the pot, I also use a metal 'spoon' to scrape the bottom, as well as try to capture some of the wood flakes floating on the top, and bringing them down into the melt. The best spoon I've found (and one that's really cheap too) is the Lee lead dipper. While I think it's about useless as a ladle, for stirring the pot, and scraping the bottom, it can't be beat!

While Gear is knowledgable, he's also great at explaining fairly technical subjects in a fashion that folks like me that never graduated from college (heck, I barely graduated from high school!) can understand! Knowledge alone is useless if you don't understand what it is, and Gear as well as several other folks here know how to explain things! Thanks Gear, and all you 'others' for doing such a good job of educating us!

[randyrat]

I learned something today..........thanks........ i never realized or understood the theory of stuff stuck under the melt. Makes sense.

[Calamity Jake]

I to us a stick to flux me bottom pours (3) and I have modified a old table knife by grinding the blade tip to match the radius in the bottom and added a long wood handle, it allows me to scrape a lot more area at one time.

After a good flux I add kitter litter on top, it cuts the oxidation, helps hold in the heat and
when adding the sprus back in they stay on top, melt and flow thru the KL therefore few or no
inclusions to deal with. It also does away with having to flux each time I turn the pot on just
scrape with the knife stur with a stick and go to casting.
When the KL is about 50% dust I remove it, flux good and add new.

[Three44s]

Calamity Jake,

I like your idea on grinding a knife to fit the bottom of the pot!!

That would beat my old spoon seven ways from ........... Thank you sir!!


Three 44s

[sundog]

The best spoon I've found (and one that's really cheap too) is the Lee lead dipper. While I think it's about useless as a ladle, for stirring the pot, and scraping the bottom, it can't be beat!

That's because it has a stright shank. Put about a 45 degree sweeping bend (adjust as necessary) in it so that you can actually pick up a puddle of melt and pour. I've been through at least two handles on mine and use it all the time. If and when it ever wears out, I have a replacement, new in package, standing by.

[bigted]

very cool guys...ive learned a bunch here from all and my casting is proof of the learnin...lol.

ive been putting back the sprue and culls from time to time as well so will refrain from doing so and see if i can stop getting so many inclusions in me boolits. my boolits are so much more consistent now and the culls are very few thanks to this thread alone.

again...thanks all for the helpful and well written tips for this sometimes thick headed ol hummer.

[geargnasher]

I to us a stick to flux me bottom pours (3) and I have modified a old table knife by grinding the blade tip to match the radius in the bottom and added a long wood handle, it allows me to scrape a lot more area at one time.

After a good flux I add kitter litter on top, it cuts the oxidation, helps hold in the heat and when adding the sprus back in they stay on top, melt and flow thru the KL therefore few or no inclusions to deal with. It also does away with having to flux each time I turn the pot on just scrape with the knife stur with a stick and go to casting. When the KL is about 50% dust I remove it, flux good and add new.

Another excellent way of casting, especially in low ambient temps or if doing it outside in a draft. They keys are, like you said, flux well and scrape the sides and bottom of the pot to work the crud to the top, then add the insulator. If using sawdust and just leaving it on the surface, it can support small sprues and let them melt back in without sinking the oxide skin to the bottom, in fact it reduces the oxide as they melt, but it won't support boolit culls and heavy sprues nearly as well as KL will.

Your reshaped knife idea is outstanding, thanks for sharing that. I'm adding that to my list of "must haves" for the constantly-being-improved casting setup I have.

Gear