Well.... "Cast and learn", I suppose.

[Beagle333]

I used to put ground clay, or kitty litter, on the top of my melt to keep the oxygen away from the top of the alloy (a RCBS Pro Melt) as it was used from the bottom. I had read that several people do this and it seemed to work great. I would just put the sprues back on top of it later and give em a poke and they would sink back down and the clay would float again. I did this fairly successfully for nearly a year now, but I started having more inclusions in my bullets and a higher cull rate and it was puzzling me. So today I skimmed the pot clean and started draining it. The more I drained, the more ground clay I found, clinging to the sides of the pot. I thought I had been doing a good job of scraping the sides of the pot when I would stir in some wax and add ingots/sprues, but apparently not. There was quite a lot of clay dust down in there and also stuck to the bottom. I thought the stuff was s'posed to float.

So now I'm going to try sawdust on top of the melt and see how that works. Maybe it will float better and also help float some of the stuff from the bottom when I'm digging at it with my paint stirrer.

I already resmelt any ingots/weights that I buy, using another pot, and use lots of wax and sawdust to clean it before making my ingots that go in the casting pot.

[straight-shooter]

Taken from a very informative article pertaining to the use of sawdust

Of particular interest to the bullet caster are calcium, aluminum and zinc -- all of which are difficult to reduce and all of which cause casting problems if present in any significant amount (they muck up the surface tension of the alloy and prevent the alloy from filling out the mould properly). As the sawdust chars, it can be thought of as a kind of activated carbon. Both the lignin's of the original sawdust and the oxygenated sites of the activated carbon are very effective at binding metal ions like calcium, aluminum and zinc. Thus, the advantage of sawdust is that it does both jobs, returning the tin to the melt and removing the problematic impurities. Sawdust has the added benefit of being free.

I generally use walnut sawdust, left over from my grip-making activities. Different types of wood are known to give rise to grades of activated carbon with different activities, but whether or not this would make any difference to the bullet caster I don't know (doubtful, any sawdust should work just as well, and some, like cedar, redwood and pine smell awful purty!). A heaping tablespoon is just about right for a 10 lb pot, stirred in thoroughly to begin with and then left in place. Halfway through the pot, the lead-pot is stirred again, this time the activated carbon (dross) is removed. By leaving the charred sawdust on the melt for the first half or so of the casting session, a barrier is formed to slow down the oxidation of the tin, and by removing the charred dross before reaching the bottom, the sequestered impurities are removed before they can sneak through the bottom-pour spout and possibly cause inclusions.

[Beagle333]

I have read that article. Actually I had re-read it again just today as I was thinking about my problem. I had thought that I had removed the impurities with the sawdust when fluxing before putting the ingots in the casting pot, and I might well have, but the problems came from the clay sinking in the melt. The reason I didn't go with sawdust in the casting pot as well, was that it smokes and clay doesn't smoke at all. I'm pretty sure the lead was clean lead with most free metals removed, but the clay itself was sticking to everything in the pot. Even the thermocouple stem was coated all the way to the bottom. It all came out easily, as it was just dry, dusty clay, and I'll give it a good scrub with my small wire brush before refilling it, to make sure it's all clean. Hopefully the sawdust won't sink in the melt when I add ingots and replace sprues in between casting sessions.

[straight-shooter]

What I do is melt 18 pounds of lead to begin with. Then stir in the two tablespoons of sawdust and let it come to the top and then start casting. This insulates oxygen from getting to the melt. I use up half the pot and then stir the charred sawdust in the melt again. Once it comes back up top I remove it and finish casting until I have about 3/4" of melt left.

At this point I just melt a new pot of lead and start over. I don't put the sprues back in until I start the next new pot of lead.

When the charred sawdust is removed it takes any small amounts of aluminum, copper and zinc with it.

[Beagle333]

Thanks. I'm gonna give the sawdust a try this weekend, weather permitting.
I just got my first 6 cav in the mail today and I want to make some bullets rain! (A Group Buy Lee 454424)



This is gonna be sweet!!!!



I only had a double cavity before.

[straight-shooter]

Good Googly Moogly! Those look like some serious thumpers.

I always enjoyed shooting boolits similar to those at the indoor range. They always made a loud thud when they hit the backstop to the point that I got looks from people.... LOL.

[skizzums]

ya know beag, I don't flux my melts........

maybe it's blasphemy, but the way I have been doing it now is, melt down source lead and flux with corncob and walnut media(creates a lot of smoke and flames up for a second), then after original WW or whatever are cast into muffin ingots I then cook again in a clean pot for alloying, flux again with wax and walnut, then it goes into 1# ingots. so it get fluxed twice before going into the bottom-pour, and I have always had nicely poured boolits.

just me, maybe I am all wrong, but it's werkin and my bottom-pour stays pretty clean

[Beagle333]

Do you put only lead in the bottom pour and just let it skim over as you cast the lead out from below, or do you put any sort of layer on top of it after you load it up?

I'm always remelt my bought weights or ingots in a different pot and do the fluxing to make the clean casting ingots, but I do put something on top of the casting pot too, or it gets all scummy, and from what I read, that is my tin oxidizing out.

[skizzums]

as long as I keep it stirred, it doesn't cake over, but I do get some of the orangey stuff on the sides, but not as much as I did when I fluxed in the casting pot. when I first started fluxed with wax, it made my pot super dirty, then switch to sawdust, which was admittedly cleaner, but not as clean as not fluxing at all in the casting pot

[snuffy]

Beagle, the problem with kitty litter or anything else is it can get trapped against the sides and bottom of any pot by the heavy lead. You have to physically remove it by scraping with a metal spoon or curved scraper. then it can float out.

I flux as soon as I see a scum forming on the surface of the melt. Depending on the temp, that can be in only 10 minutes. Keeping the melt around 725, it takes twice as long, or enough to drain the pot to refilling level with a 6 cav like yours.

Since I started using sawdust, I don't flux at all after the initial flux when filling/melting the pot. Leaving the resulting black carbon floating on the alloy to provide a barrier from the atmosphere. Oxygen will create a oxide layer on the hot surface of the melt. Tin is much more reactive than the other two, so it oxidizes first and quicker.

Sprues and rejected boolits all have a bit of oxide on their surface. Since they're colder, they immediately sink to the bottom of the pot. If there's something on that alloy surface like kitty litter of sawdust carbon, it may get dragged to the bottom to stay there trapped by the heavy lead.

Yes, I do flux even when using ingots I myself poured when smelting them. They were well fluxed when they were being reclaimed from scrap lead.

Fluxing with sawdust will return precious tin to the alloy as well as antimony. Waxes or oil will NOT remove the unwanted AL, CU, AND ZINC, it stays in the alloy.

[Beagle333]

Thanks Snuffy. I'm definitely making the switch to sawdust.

[stubbicatt]

You fellas don't use a flux like Marvellux?

[snuffy]

You fellas don't use a flux like Marvellux?

Good God no! Marvellux is some real bad stuff. It is borax, it does clean the alloy but then it deposits a glass-like coating on anything it contacts on the inside of the pot, on your ladle, anything you use to stir or skim with. Midway used to sell some stuff, a white powder, it was the same stuff. It is also hygroscopic, (draws moisture from the humidity in the air), it will cause rust on/in your pot.

The only good part is it doesn't smoke or stink.

Using Marvellux will clean the metal of all oxides. Um, the main purpose of fluxing is reduction of oxides. Whenever metals are exposed to oxygen, they form oxides. You want and NEED to get those oxides back in metallic form reduced to metallic form from the oxide form. Marvellux does NOT do this, it removes the oxides from the alloy. This means you are loosing the tin, lead, and antimony you want to keep.

[Beagle333]

"Some of the commercial bullet fluxes are formulations that have the advantage of generating virtually no smoke or odor (in contrast to the waxes just discussed). These formulations are commonly based on borax, or other boric acid derivatives. The way these commercial fluxes work is to combine with the oxidized components of the alloy (including any oxidized tin) and form an insoluble molten borate glass, which collects on top of the melt as a dark molten crust. This process is smoke-free and cleans the alloy very effectively, but the dark molten crust must be removed to prevent inclusions in the bullets. Unfortunately, any oxidized tin is also removed in this process. Relatively little of these borate-based fluxes is needed to effectively clean up bullet metal (only about half a teaspoon is needed for a 10 lb pot), but too much can cause problems by generating excessive amounts of this molasses-like glass that sticks to the ladle and lead-pot, and can cause inclusions if not removed."

Taken from this:
http://www.lasc.us/FryxellFluxing.htm

[Mike / Tx]

Just a little tip for your sawdust to help reduce some of the smoke.

Get out your long nosed propane lighter, and when you throw your handy amount of sawdust onto the molten lead it will start to turn brown then start to smoke. As soon as you see the smoke light your lighter and touch the flame to the sawdust and it will ignite and burn off similar to when using paraffin. It will still smoke a little but not nearly as much as if you just let it smolder.

I DO realize you haven't quite got your loading room mancave quite done, but when you DO this will help out a LOT being inside and all. I do this inside my shop with the cooker sitting under the 20" box fan which blows out the back door. It sucks what little smoke still arises right out. Just one of those little tips like using the reflector from your clamp on light as a sprue funnel....

[Beagle333]

I'll put a long nosed propane lighter on my Christmas wish list. I don't have anything propane. But mebbe it would help with the smoke some.

I do have a clamp-on light.

[Beagle333]

'Just picked up another 69# of old wheel weights today. It's smeltin' time again! This is from a barrel that is about 5 years old, so mebbe they are mostly lead.
This is gonna be the last box.... really. I can quit any time I want to. I can!

[straight-shooter]

Them look like the big ol' truck weights.... thems the good uns'! Makes the bullets fly straighter I swear!

[skizzums]

your sure are a lot cleaner than the junk I get.........I betcha mine's a bit cheaper though

[Beagle333]

I'll bet yours were too! I wish I had a source for gettin' em free, or for a six pack and a pizza, but times are hard all over.

[stubbicatt]

So, nix the Marvellux for future use.

Will used tumbling media work in lieu of sawdust, which I don't have? It would be nice to find a use for that stuff.

[Beagle333]

Is anybody building a home near you? They usually have a pile of sawdust in the front yard where the sawman sets up each day. Cabinet shops are usually also happy to get rid of their sawdust. You can also buy hamster or pet bedding in the bags anywhere from WalMart to Target to PetCo and that is just wood (cedar) chips. Not ground as finely as sawdust, but will end up as carbon ash just the same. Paint stir sticks are great for stirring to break loose the dirt and crud that sticks to the side of your pot. Just be sure that ANYTHING that will end up underneath the melt is dry. This includes stir sticks and the stuff you're stirring in there. Truth be told almost any organic (carbon containing) material will work, from dried leaves to grass clippings, but most think sawdust works the best.

I have never tried my used walnut media. I guess it might work, since it is just nut shells, but I have access to a LOT of sawdust here.

[straight-shooter]

A few days ago I needed more sawdust and asked the neighbor that has a table saw if I could use it. Once I ran through a couple of boards I collected the sawdust and swept out his entire garage for the favor.

[gwpercle]

Stubbicat.....I confess to using Marvelux, on page 57 , Lyman Cast bullet Handbook #3, says to us it. Page 17 of the RCBS Cast Bullet Manual #1, shows a can, sitting next to the pot and states the modern commercial fluxes are the best.....these being my only source of guidance back then, I followed their instructions.
Now the trick is don't use too much, I use 1/4 to 1/2 teaspoon for a pot with 12 to 15 pounds of alloy. If you get a molten glass layer on top and/or a buildup on the pot walls....that's TOO MUCH . I find it better to do 2- fluxes with 1/4 teaspoon each than one flux with 1/2 teaspoon...just seems to clean better.
After doing my two small Marvelux fluxes, before I get to casting , I flux again with just a drop or two of melted beeswax. Touch a beeswax cake to my hot stirring spoon and get just a couple drops in it and stir into melt. Not sure why but the beeswax gets the metal really clean and all blended. Again, don't use too much, it smokes and will flash to fire so use a small amount.
All of the fluxes work, the trick is using the proper amount.
And in the middle of a casting session, if the melt needs another flux I will use the cedar shavings from our wood pencil sharpeners, cedar smells nice and shavings reduce to charcoal quickly, stir them in and resume casting.

Gary