Rainbow Boolits

[NM156B]

O.K., researched past threads on the site for info on inclusions, dross, flux, and rainbows. Think I solved all my issues except for the last one, what causes the rainbows in the inclusions.

Still a relative newbie.

Since I fire black powder for 1860 Colt Army pistol, I use virgin lead, and for flux I use pure bees wax and sawdust, and for stirring and dross removal I use stainless steel spoon (Onieda).
Everything was fine for first 10 casting sessions or so, but then issue started slowly. I see the bottom pour pot as akin to a Texas chili pot, you always use the remains of the previous batch to seed the new one, so I figured it was something I was doing that was “additive” somehow.

Even after skimming I started getting a rainbow crystalline dross film immediately form on the top layer of the pot. Lead started freezing at the spout, and eventually even propane torch on it would not help.

Image below is straw that broke the camel's back (Though I will keep it, since it is kind of pretty... grin/sigh)

I ended up emptying the pot and digging out brittle brownish buildup from inside the spout and a thin layer on the edges of the pot. This in the spout was probably acting as a partial stopper and probably acting as refractory and insulating the nipple, hence the freezing. Threads on this site infer that is most likely my sawdust over time. Ditto on inclusions could be from the sawdust buildup and stirrings as well, but what is causing the rainbow blue/pink/purple/gold sheen that only shows up in the dross and inclusion? Can stainless steel over time be changing the chemical makeup and causing an issue?

[osteodoc08]

Melt was too hot. Get a thermometer.

[NM156B]

Tried it hot and cold (per suggestion from other threads researched), same effect. The above was a pour on low immediately after initial melt. I was going to measure it but got so frustrated simply cleaned the pot. Expected frost if too hot, but perhaps my pot temp dial is broken, will record empirical data if it starts showing up again with next several batches.

[Dusty Bannister]

"I use virgin lead"

Lead alone does not frost. The melt is too hot so you speed up the oxide formation. Usually that tan debris is just dirt and will dissolve in water as described in how to clean a pot with water. Yes, you are getting something in the pot besides clean lead. Your reading might have suggested that saw dust is great for cleaning lead when rendering scrap. Some of us never want saw dust in our casting pot.

Did you attempt to clean the pot nozzle if it started running slow? Does the pot have a pour control, or just the simple Lee 10 pound pot. Did you scrape the sides and the bottom of the pot when fluxing with beeswax or candle wax? Did you skip fluxing because it is "Virgin lead"?

[NM156B]

Did you attempt to clean the pot nozzle if it started running slow? Does the pot have a pour control, or just the simple Lee 10 pound pot. Did you scrape the sides and the bottom of the pot when fluxing with beeswax or candle wax? Did you skip fluxing because it is "Virgin lead"?

Thanks for the lead alone does not frost fact, new piece of knowledge puzzle filed away for future reference. Yes on the 10lb pot, before emptying it I tried drilling the hole when unit was off (did not help) and the nail trick when on (would start to flow and after a pour or three would quickly taper to a slow drip with freeze, propane torch on tip no help either, hence my original surmise that I had a true dirt clog in the drainpipe). To each batch run I would add a pea size piece of refined beeswax straight from the beekeeper (really), lightly stir, then sprinkle a couple of pinches of sawdust on top. Never "scraped" the sides while stirring, wasn't smart/learned enough to know that crud would form there, so only skimmed the dross off the top.

[osteodoc08]

Sorry my answer was short earlier. Trying to see patients in between scanning the site.

When pure lead melts and gets hot it will oxidize and give the rainbow effects. Since there is not tin or antimony in it, it will not frost.

Specks of junk and whatnot is from trash in the melt. I never use sawdust in my casting pot. That just invites inclusions and whatnot.

If you melt the oxidized lead, it's still gonna have lead oxide and give you rainbows even if you don't get the temp up too high.

You can add the beeswax and keep temp low as it melts and hold the temp there and keep a layer of melted beeswax and keep stirring. You'll need to reduce the oxide back into the melt.

Hope that's a better answer.

[NM156B]

Sorry my answer was short earlier. Trying to see patients in between scanning the site.
When pure lead melts and gets hot it will oxidize and give the rainbow effects. Since there is not tin or antimony in it, it will not frost.
Specks of junk and whatnot is from trash in the melt. I never use sawdust in my casting pot. That just invites inclusions and whatnot.
If you melt the oxidized lead, it's still gonna have lead oxide and give you rainbows even if you don't get the temp up too high.
You can add the beeswax and keep temp low as it melts and hold the temp there and keep a layer of melted beeswax and keep stirring. You'll need to reduce the oxide back into the melt.
Hope that's a better answer.

PERFECT!!! Thanks!

[Grmps]

I would be tempted to re-smelt and flux a couple times with sulfer, Look's like there is something in the lead that shouldn't be there

[OS OK]

Here's the 'bible' so to speak about this craft...it gets a might technical at times but you can wade through easily enough...I wiKi the terms I don't understand, sometimes that helps...sometimes I have to keep on wading...

http://www.lasc.us/Fryxell_Book_Chapter_4_Fluxing.htm <-- 'Fluxing'

http://www.lasc.us/Fryxell_Book_Contents.htm <-- 'Contents page' from:From Ingot to Target:
A Cast Bullet Guide for Handgunners ©

[Thumbcocker]

I keep a layer of clay based cat litter on top of my pot to reduce oxidation.

[Grmps]

I keep a layer of clay based cat litter on top of my pot to reduce oxidation.

Similar principle: I cover the lead with pine sawdust, burn it off, flux in with a potato masher then wire whisp leaving a layer of grainy dross on top that helps prevent oxidation and splash from returning sprues to the pot.

[wimms]

Bismuth?
https://www.google.com/search?q=bism...ystal&tbm=isch

[NM156B]

Here's the 'bible' so to speak about this craft...

Nice primer, but argh I am confused, the "best" solution according to the article is sawdust! : "Vigorously stirring in a heaping tablespoon of sawdust into a pot full of bullet metal does a fine job of conditioning and protecting that alloy." My head hurts, this line implies the boolit casting phase...

This goes back to other threads on the forums here, the only "physical contamination" I added to my casting pot is super fine sawdust (literally dust), two pinches, in each batch run and the beeswax, are the inclusions in my picture from the sawdust or the lead oxide (or both?)? Since I am using virgin lead, I assume that I only need a barrier, so in theory the wax alone should work...?

[OS OK]

Yep...sawdust in the pour pot is flirting with trouble...however when smelting I use it by the handful, even start out throwing a handful under the Pb before it melts.
In the pour pot I like just the paraffin...the idea is to separate oxygen from the melt...funny thing, I fully expect it to burst into flames but I jump every time it does!

From Ingot to Target:

Chapter 4
Fluxing the Melt

Is there anything that combines these two modes of operation so that we can get all three of the desired attributes? Fortunately, there is. What’s more, you probably already have a pile of it in your shop. It’s good ol’ fashioned sawdust (hold the motor oil, thank you). The benefits of sawdust are that it‘s a sacrificial reductant that can reduce any oxidized tin back to the metallic state, and it‘s cheap enough that the caster can use enough to form an effective barrier layer to protect the alloy from subsequent oxidation. What’s more, as the sawdust chars on top of the melt, it forms activated carbon, which is a high surface area, porous sorbent material that has a large number of binding sites capable of binding Lewis acid cations like Ca, Zn and Al. So it not only keeps the tin reduced and in solution, but it effectively scavenges those impurities that raise the surface tension and viscosity of the alloy (Al, Zn and Ca), keeping the alloy in top shape for making good bullets. Vigorously stirring in a heaping tablespoon of sawdust into a pot full of bullet metal does a fine job of conditioning and protecting that alloy. Sawdust doesn’t really qualify under the formal definition of “flux” as it doesn’t produce a fusible slag, but it does very cheaply and very effectively accomplish the three primary goals that we set out for cleaning up bullet metal. Reduce, remove and protect, sawdust does it all!

In trying to make the best use of sawdust, I feel it's best used in the smelting of the Pb, in the ingot making phase...and do a good job there so when you get the ingots to the pour pot all that is needed is to prevent oxidation and reduce the little bit of Sn oxidation that occurs...paraffin does just that and that's all it does.

[SkookumJeff]

I hate to be a contrarian, but I use sawdust in my bottom pour pot exclusively. I've tried bees wax and candle wax, leaving a layer of melted wax on the top surface, but it eventually chars or burns and makes a mess of my pot, caking burnt wax on the sides of the pot, which I have to scrape off to clean. I like a clean pot. When I cast boolits I add a couple of tablespoons of sawdust to my pot, let it char and then spread it out and leave it on the surface while I'm casting. To my knowledge, I've never had trouble with occlusions. How do I know? I weigh my boolits. They are within 1 grain of tolerance. I'm a big fan of Fryxell, and that's why I use sawdust in my casting pot. The one caveat I would add is I don't like to let my 20 lb pot get below 1/2 empty. When my pot gets low I will spoon out the charred sawdust from the surface, add alloy to refill, let the temp stabilize, add more sawdust, let it char, spread it out and keep on'a casting great boolits. - Skook

[dondiego]

Leaving a layer of wax of any kind in a hot pot seems like way too much wax to me. I use a pea sized lump at the most and throw it in my pot along with a paper match which ignites and burns off while I stir. The surface comes out real clean with minimal skimming.

[SkookumJeff]

My understanding, gained from the Fryxall work From Ingot to Target (chapter 4) is that oxidation of the lead will occur if the top of the melt is exposed to oxygen. To prevent this oxidation you need a barrier between the melt and the oxygen. One of the purposes of a flux is to create that barrier to prevent oxygen from reaching the top of the melt. From Fryxall's work:

Ideally, the flux material could also be a cover material and form a barrier layer to protect the molten metal from subsequent oxidation, thereby maintaining optimum casting properties throughout the course of the casting session. We also want to prevent the oxidation and loss of arsenic. Arsenic oxides have very high vapor pressures and are readily lost through evaporation, not only depleting the alloy of a potentially valuable component (arsenic allows the alloy to be heat treated, if desired), but also creating a significant health hazard to the caster. A reducing cover material prevents this loss.

As I've stated I tried wax to create this barrier and did not like how it performed. Sawdust has been much easier to use as a cover material and effective in preventing the oxidation that would otherwise occur on the top of the melt. I don't stir this material around when I add it to my casting pot. I let it char and then spread it carefully across the top of the melt to cover the entire top of the melt. From then on I cast boolits, leaving the top of the melt alone. My alloy is cleaned during smelting so I see no need to stir the flux in to the alloy. I simply want to use this material to lay on top of the melt to prevent oxidation. I should note that I don't add any material back to the pot while this cover layer of charred sawdust is on top. Before I add any more alloy to the pot this cover layer is removed. This is what I do and why I do it this way. Works for me.

[David2011]

The experiences I’ve had with sawdust mirror SkookumJeff’s. I used some ingots that someone gave me. I got inclusions in my boolits from those ingots but fixed the problem by fluxing them again in the casting pot with sawdust. Every batch since gets fluxed with a bit of sawdust and I’m happy with the results.