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X-man
04-10-2005, 02:18 AM
Was having a discussion on another board the other day and the subject of tin and wheel weights came up. Back when Shooters.com was still up and we had the Cast Bullet Board to loaf around on, I was taught that care must be taken to properly flux when melting down WW and to stir well to ensure uniformity of the alloy. A big concern was to NOT skim the shiny metal that floated to the surface, along with the crud and steel clips, as that was the tin. Got a guy on the other board telling me I'm full of $hit, to use his words, "Once amalgamated, tin does not separate from the alloy and therefore you can't skim it off." Can anyone offer clarification on this?

NVcurmudgeon
04-10-2005, 02:24 AM
X-Man, There was an article in Handloader years ago by a metallurgist from a company that made lead alloys. He said that lead alloys do not gravity separate. In my crude home foundry, I can't prove him wrong, so I'll take his professional word for it. Welcome to our new home, curmudgeon

Buckshot
04-10-2005, 04:49 AM
...............Nope, once melted together they do not gravity seperate. HOWEVER, metal in contact with oxygen WILL oxidize. Rust is what iron does. Form a dull grayish surface is what happens to the boundry layer on a pot of hot boolit alloy. And the hotter it is, the more nergetic the reaction is. Add to that the disturbance of dipper casting constantly exposes a fresh area to tthe air. If you just sweep this off and toss it when it appears you are depleting the tin and antimony content.

Naturally you're also removing a bit of lead, but the lead usually makes up 92% or more of the alloy, so tin/antimony losses represent a larger percentage of the whole.

A fact as that when the Hot Type (linotype) machines were state of the art, overtime the alloy would have the tin 'burned' out. Places bought enrichment alloy to replace the lost metal.

....................Buckshot

utk
04-10-2005, 05:31 AM
Following Buckshot's reply...

When tin oxidizes it grabs hold of oxygen atoms from the surrounding air and thus forms tin-oxide (SnO). To get back to pure tin, we need to remove those oxygen atoms. This is done by fluxing, i.e. adding carbon in some form, e.g. motor oil, sawdust, paraffin etc. The carbon atoms in the flux steals the oxygen from the tin oxide, freeing the tin atoms to join their buddies down in the melt. The carbon and oxygen atoms combine into carbon dioxide (one carbon atom and two oxygen atoms) and drifts away into the air.

That's what I've been told anyway and it gives a meaning to flyxing!

Kitty litter is supposed to isolate the melt from the air and slow down the formation of tin-oxides, maybe it has some fluxing properties as well?
I stopped using kittylitter as there formed grey clumps in it and I was afraid it was tin oxide. Better having a shiny metal surface so I could see when it was time to flux.

When cleaning wheelweights (outdoors), I use a candle for fluxing, simply dipping the end of the candle into the melt for a microsecond, it smokes like mad, though. When casing boolits idoors I use Marvellux, or a wooden stick to stir the melt.

utk

NVcurmudgeon
04-10-2005, 12:07 PM
I believe that I am avoiding tin depletion by using an RCBS dipper with a fin on it that allows me to rake myself a clean shiny surface to ladle from every cast, and fluxing about every dozen casts. Leastways, I never find any dross in my boolits, and my skimmings are 99.44% lightweight, coarse. gray powder. Any metal that adheres to the powder is FRESHLY fluxed. (No fox in a forest fire comments, please.)

fatnhappy
04-10-2005, 12:35 PM
I believe that I am avoiding tin depletion by using an RCBS dipper with a fin on it that allows me to rake myself a clean shiny surface to ladle from every cast, and fluxing about every dozen casts. Leastways, I never find any dross in my boolits, and my skimmings are 99.44% lightweight, coarse. gray powder. Any metal that adheres to the powder is FRESHLY fluxed. (No fox in a forest fire comments, please.)

NVcurmudgeon has a very good point. Tin can only oxidize in contact with an oxygen source. The layer of SnO on the surface of the melt actually forms a "limiting" barrier in much the same manner as rust blueing on our rifles. Problem is, you're always disturbing the surface and breaking the barrier constantly.

I just use candles too. My wife never notices when 1 of 1000 disappears.
As for the original question, cosoluable liquids form homogeneous stable solutions to the saturation point of their constituents.

44man
04-10-2005, 06:52 PM
I use parrafin and was running low so I told the wife to get me a box. She came home with this HUGE block that must weigh 10# or more. Said it was cheap. I don't know where she bought it but it is enough for 2 lifetimes.

buck1
04-11-2005, 09:25 PM
I have wondered about tin oxide, and how to re mix it. I guess dad was right " always flux before you skim". .....buck

MARCORVET
04-12-2005, 02:35 AM
Do you disturb the surface and break the barrier because you ladle pour, or does this also take place with a bottom pour?

utk
04-12-2005, 02:55 AM
NVcurmudgeon has a very good point. Tin can only oxidize in contact with an oxygen source. The layer of SnO on the surface of the melt actually forms a "limiting" barrier in much the same manner as rust blueing on our rifles. Problem is, you're always disturbing the surface and breaking the barrier constantly.

I just use candles too. My wife never notices when 1 of 1000 disappears.
As for the original question, cosoluable liquids form homogeneous stable solutions to the saturation point of their constituents.

I don't believe that a layer of tin (or lead) oxides stops further oxidation. I think the tin will keep oxidizing and making the oxide layer gradually thicker and thicker.
utk

X-man
04-14-2005, 12:19 AM
Thanks for all the replies guys. Looks like my memory failed me on this one. Good to know though. Once I get some pesky house renovations out of the way, I'm hoping to get a couple of real marathon casing sessions on the go to build up my reserve for the upcoming shooting season.

fatnhappy
04-14-2005, 12:41 AM
I don't believe that a layer of tin (or lead) oxides stops further oxidation. I think the tin will keep oxidizing and making the oxide layer gradually thicker and thicker.
utk

How can you oxidize if you're not in contact with oxygen?

you'll reach an equilibrium state and stay there absent other influence.

utk
04-14-2005, 03:19 AM
How can you oxidize if you're not in contact with oxygen?

you'll reach an equilibrium state and stay there absent other influence.

I "think" the oxide layer is rather porous and therefore oxygen atoms will "seep" through, maybe at a slower pace as the layer grows thicker.

But, let's not disagree about this.
Try for yourself and report back to the board. I will continue to flux everytime I add fresh metal to the pot. Since I bottom-pour, a little oxides on the surface is of less importance to me.
utk

Char-Gar
04-14-2005, 11:51 AM
I am probably doing this wrong, but I use a bottom draw furnace and when I first fill up the pot. I think put about 1/2" of kitty litter and don't flux again. I just keep adding alloy to the pot. I have not noticed oxidized material in the litter, but don't really look that close. The bullets are free from dirt and such, have uniform (within normal limits) weight and hardness and shoot well.

Without the litter, I have to flux every 10 minutes or so to keep a shiny melt. With a dipper, it starts to accumulate crud and oxides on it after five or so cast, if I don't flux. Way to much trouble and it doesn't produce, for me a least, any better bullets, than a bottom draw with kitty litter.

When melting WWs, I melt, flux and skim of the clips and dirt. Then flux and skim again. I then add a little tin, flux again and pour the clean alloy into ingots. I might flux once more about halfway down the pot. I get very clean and uniform alloy that way.

This may or may not be the wayk to do it, according to science and theory, but I am not about to change it, as it works for me.

Ballistics in Scotland
04-14-2005, 05:49 PM
While fluxing the alloy is the right thing to do, its importance can be overestimated. A pound of alloy might contain an ounce of tin, and if it all oxidised and was removed, it would be more than ounce of oxygen. I can't remember producing more than a small fraction of this.

If you use an open ladle, however, fluxing does remove most of the risk of pouring some oxide into the mould.