Fluxing bottom pour pot

[glockky]

Do you all put anything on top of your melt in a bottom pour pot to keep lead from oxidizing so badly?

[500MAG]

I stir it with a wooden spoon. It forms a charcoal like layer on top.

[LUCKYDAWG13]

i just use sawdust and a few boolits with lube on them

[docone31]

I use Kitty Litter. Makes a good pull for contaminants. I use vegetable oil for a kind of flux and it works well. Smokes a little but the melt gets real shiney.
I also scrape the bottom of the pot when the melt is liquid. I get sheets of crud that floats to the top. That is with melting my ingots in a seperate pot prior to introducing to the casting pot.
Crud is a fact of casting.

[preachinpilot]

I use lard. Past on by an old timer. It does not collect moisture and does not fowl your molds. Left on the top it will turn to ashes. Put a teaspoonon top when it is just about to solidify at the end of your casting session and it will go down the inside of the lead as it shrinks from cooling. Lard then lubricates the pot, valve etc. ABSOLUTELY THE BEST>

[Bzcraig]

I use lard. Past on by an old timer. It does not collect moisture and does not fowl your molds. Left on the top it will turn to ashes. Put a teaspoonon top when it is just about to solidify at the end of your casting session and it will go down the inside of the lead as it shrinks from cooling. Lard then lubricates the pot, valve etc. ABSOLUTELY THE BEST>

First time I have heard this and it sounds pretty good to me. Up to this point I use sawdust and stir it in good with a paint stir stick. I used to stir with a stainless spoon but found the paint stick, when pushed against the bottom goes a long way to keeping the bottom of the pot clean.

[el34]

Pine shavings small critter litter, a layer completely covering it. I gently stir it a minute or two to get it charred, then just let it do its magic. I never skim it off, just add more as it disappears. No oxidation ever.

I just increased my pot temp to 700, up from 650, to make the little 2-cavity 102gr mold work better. Lower temps helps avoid oxidation.

[geargnasher]

Pine shavings small critter litter, a layer completely covering it. I gently stir it a minute or two to get it charred, then just let it do its magic. I never skim it off, just add more as it disappears. No oxidation ever.

I just increased my pot temp to 700, up from 650, to make the little 2-cavity 102gr mold work better. Lower temps helps avoid oxidation.

Basically what I do. Scratching around on the bottom of the pot with anything wooden trapped ashes down there when I did it, and the ash caused dross inclusions in my boolits. I scrape the sides with a stick of some sort because it wipes the oxide/dross clingons right away (reduces them on contact, unlike a metal instrument) but use a metal spoon to scrape the bottom and bring junk up the sides of the pot where it can be removed or just soaked up with the ashes from the charring sawdust and skimmed when the pot gets low and needs refilling.

The sawdust adsorbs oxidized impurities, reduces the good oxides back to elemental metal, and the ash layer left as it chars prevents further oxidation of the top of the melt.

Kitty litter is a fine method of sealing the top surface of the melt and for keeping heat in the pot if casting in a cold or drafty environment, but it doesn't reduce oxides at all and really doesn't do anything for sucking up impurities from the alloy.

Gear

[bangerjim]

Bees wax and anything that will burn! Normally I use walnut or alder sawdust from the shop, but recently I have been using the dried leaves that are falling off my Chinese pistachio tree over my casting area outside my back shop. Works well and smells great!

I leave the stuff on the top and skim only occasionally.


bangerjim

[geargnasher]

Bangerjim, beeswax isn't flux. It doesn't remove impurities. It does make a great sacrificial oxide reducant, but that's it. It isn't comparable to sawdust or borates for cleaning contaminant metals from the stuff we want to make into boolits.

Gear

[bangerjim]

Yes, wax, of any kind, is a reducer only. When used in combo with fluxes, it cleans and puts the tin back in. We DO want that tin back in there rather in the dross pan.

At least all my testing shows that. Wax alone is only a reducer. That is why I said "...and anything that will burn."

You need to use BOTH. My lead casting pours are clean, shiny, and fly straight.


bangerjim.

[geargnasher]

Sawdust IS both.

Wax does help get the tin reduced quickly at the beginning, though. Since all metal oxides are adsorbed by the charring sawdust, it's good to get the most easily reduced stuff (tin, lead, antimony, in that order) all reduced right away so it can't get trapped with the oxides of the stuff we want to remove, and that wax is fairly ineffective at reducing, fortunately.

That's why I prefer rosin-rich yellow pine shavings, it has an extra dash of quick-acting reducant for the stuff we want to keep in the alloy, same as adding a bit of wax with other kinds of sawdust.

Gear

[detox]

I use Vita-Flux or parafin or beeswax. Keep the sawdust on the shop floor where it belongs.

[jmort]

"That's why I prefer rosin-rich yellow pine shavings..."

Yes indeed

[geargnasher]

I use Vita-Flux or parafin or beeswax. Keep the sawdust on the shop floor where it belongs.

Good for you.

Gear

[uglysteve]

Could someone please explain to me why this is necessary? I am going to start casting soon and would like to know the hows and whys of all I can.

[Iron Mike Golf]

In a nutshell:

Even if you have a perfectly clean pot and perfectly clean alloy, the alloy will oxidize as it sit molten in the pot. The oxides have a hight melting point than the temp you cast at. The oxides are lighter than the alloy so they should (and mostly do) float to the top, but a lot can (and does) remain trapped under the weight of the molten alloy. It can get dragged to the spout in a bottom pour flowing alloy by where it will either go into the mold or get stuck in the spout.

If it gets stuck, it can plug up the spout. If it gets into the mold, your boolit has a place of lower density than the rest of the boolit. If it's big enough, it can throw the center of gravity off the centerline of the boolit and degrade accuracy.

Read this: http://www.lasc.us/Fryxell_Book_Chapter_4_Fluxing.htm

Actually, you should read the whole thing and also get a copy of the Lyman Cast Bullet Handbook. Some like 3rd Edition, some, the 4th, others recommend both. Lots of cast load data in those, too.

[uglysteve]

Thanks. I'm reading "from ingot to target" now. I'll look into getting the other one too.