Weird melt problem

[brimic]

I commited one of the cardinal sins- I rendered w/ws in my casting pot....I'm almost wondering if it might be a possible cause, but read on.

Tonight I tried casting and got a huge amount of yellowish ashy slag. I fluxed the crap out of my melt until it was shiny. I'm using a Lee Pro Pot IV and am using the bottom pour for casting. I had a tough time getting moulds to fill out, in fact I ran the pot 1/2 empty before I started getting a few decent bullets. When th epot was 1/2 empty, I noticed that what was left was mostly the yellow slag again. I scooped as much as possble back out, put my crap bullets back in the pot, remelted, and fluxed again. Once again I got a lot of yellowish looking slag. Iran the pot 1/2 empty again and found more slag. I finally just emptied the pot, scraped out as much crap as I could, and pitched all of the lead I was working with tonight.

I wonder if my my melt got poisoned with zinc?

I also started rendering lead with a camp stove setup, and am going to scrub my casting pot before I use it again.

Another possibility I thought of- I had introduced a 1lb bar of 50/50 solder to the melt last time I casted. I'm running the pot wide open on heat to try to get my 6.5 kurtz mould to fillout. Could this be tin oxidizing out of the melt?

On the bright side, I got maybe 200 acceptable 6.5 boolits to play with for now.

[David R]

Bummer........

No you probably did not get zink, you only commited one sin. Cleaning wheel weights in your bottom pour............. you are forgiven, and for pennance, you can scrub your bottom pour pot. You could even take the lead you pitched and put it on your campstove and flux it again. Make sure when you flux wheel weights you stir and stir. I take my skimmer and run it along the bottom of the pot then lift. You will be surprised how much crap will come up. The weight of the lead holds stuff on tht bottom of the pot. I have even dragged up small WW clips.

To clean MY bottom pour, I have thrown some boolit lube in the pot when it is empty and run it right out the spout. Makes a mess, stinks and smokes, but it does seem to clean where I can't reach.

Tin oxadizing would show as silver grey scum on top of the melt. Fluxing will put that back into the melt. Anything else is junk.

Good luck with your boolits. Once those are gone, maybe you can pour some more :)

David

[FISH4BUGS]

[QUOTE=brimic]I commited one of the cardinal sins- I rendered w/ws in my casting pot....

Well I am surely going to burn in Reloader's Hell for my sins. I have been doing this for all my years of casting bullets. I have never had any problems whatsoever doing this.
What is so bad about rendering w/w's in your casting pot as long as you clean it out after you do that?

[David R]

Fish4bugs,

If its a bottom pour, its hard to clean for me. I rarely (almost never) let mine run out of lead. So to clean it I would have to drain it.

If it works...Great. Doesn't work for me.

As they say "Your Milage May Varry"

David

[brimic]

Well I didn't exactly clean it after rendering w/ws. I would always leave it 1/2 full when cooling.

[Linstrum]

Hey there, brimic,

The yellow stuff could be from either zinc contamination or bismuth, probably bismuth. Here's how to tell. Zinc oxide has a property that is very peculiar, which if pure is bright canary yellow when very hot but snow white when cold. Actually it doesn't look like snow, it looks enough like powdered sugar to fool most folks. If zinc oxide is mixed with dark stuff in the dross it will look brown instead of yellow, though. Welders know all about zinc oxide changing color when hot. If you want to see how zinc oxide changes color take a galvanized nail or piece of galvanized wire, like from a fence, and heat it with a propane torch. The zinc will oxidize and you will see it change color in and out of the flame. Bismuth oxide is also bright yellow but it stays yellow when cool. If your slag was yellow after cooling it is probably bismuth oxide. Where did the bismuth come from? It is one of the main ingredients used in some kinds of non-toxic lead-free plumbing solders and also used as the main ingredient in low temperature solder, the so-called "match solder". It is also the main ingredient in Cerro-Safe (also called Cerro-Bend and Wood's metal) used for making chamber castings, and the low temperature fusible links used for fast-blow electric fuses and ceiling fire safety sprinklers. If somebody removed a bunch of fire sprinklers and recovered the bismuth-tin alloy tabs used for the low melting point valve closers it could have been mistaken for lead and thrown in with the lead scrap alloy at a mom & pop wheel weight making business. The little back-alley wheel weight making businesses don't care what they use as long as it melts and is cheap.

Bismuth is not necessarily bad stuff, though. I use bismuth in some of my boolits because it makes a very slippery and hard alloy without being brittle. Before running out and getting some bismuth to use, though, the bullets that use it can be cranky because the melting point is a bit lower than normal and gas checks MUST be used and no hot burning double base powders like Red Dot or Bullseye used. Hot powder and a bismuth alloy bullet might give you snake shot and only half a bullet coming out of the muzzle!

A word of caution about colored dross. When melting lead alloy of unknown origin and you see a nice cocoa brown color that you have never seen before in your experience, throw the stuff out. The cocoa brown color is from cadmium, and cadmium specifically kills heart and kidney cells. The cadmium oxide color looks just like Hershey's cocoa powder. Cadmium used to be used in the special alloy for the low melting point fusible links for fire sprinklers. The low melting point alloys that contain cadmium are called Rose's metal and Lichtenberg's metal, among several with low melting points. Lead will alo make a very pretty cocoa brown color when heated, but at much higher temperatures and you need a propane torch or oxy-acetylene torch to produce lead oxide. Cadmium is also used for electroplating small items like screws and is comparitively safe in that form because it is not volatile, unless heated.

[StarMetal]

Bismuth is also found in the stomach medicine Pepto Bismo...but you can't melt it down to make bullets out of it.

Joe

[FISH4BUGS]

Well I didn't exactly clean it after rendering w/ws. I would always leave it 1/2 full when cooling.

I DO clean mine. After rendering down and making 1 lb ingots from a 5 gallon bucket of ww's, about 80 lbs or so (that usually takes a looooooooong afternoon), I always empty the pot (bottom pour) and clean it out. There is always some little bits of dirt or something else in there. I can then start my usual casting routines of 5 lbs ww to 1 lb linotype. Most of the time the lead never empties out of the pot when I am casting. I just keep throwing in 5/1 (6 lbs at a pop) when it gets down, plus add the sprues and bad bullets.
I always start with an empty pot. Since I cast with mostly 10 cavity Hensley & Gibbs moulds (I use cast lead bullets in all my submachineguns and everything else except 223) I can go through a fair amount of lead in a day's worth of casting. On the other hand, it is fairly easy to go through 1000 rounds in an afternoon of shooting the subguns.
I guess I never realized that I was doing something wrong. Oh well....as an earlier post said....you mileage may vary.

[boogerred]

if your melting WW,s in a lee bottom pour and leaving it half full your still going to have a lot of crap under or in that heavier metal.the way the valve rod angles from top/rear to bottom/front makes it almost impossible to scrape the sides and bottom and stir the crud to the top like you need to. youl always have junk suspended in the good alloy. i melted WW,s in my bottom pour ONCE,never again. only good,clean metal goes in my B.P. i feel safe leaving an inch or so of clean metal in my B.P. to speed heating for the next session. melt and clean WW,s and make ingots with something else. save the B.P. for clean metal.

[brimic]

Lindstrum- the best way to describe what I had when it was hot was a bright yellow/orange 7-eleven Slushy drink. It did turn somewhat brown on cooling. My best description would be it turned from yellow to a yellowish brown ashy mix.

The lead I'm using is all wheel weights, so by your description, I think it might be zinc.

[brimic]

Another question-

does zinc allow with lead or does it seperate out? Now that I think about it, my melt looked nice, shiny and slivery when full, when it drained down is when I started seeing all of the crud in the bottom and the glowing.

[Buckshot]

............Zinc does alloy with lead to a certain percentage. Most metals will dissolve a small fraction in a lead melt. Iron or steel is used for lead as other metals either don't stand the heat (like aluminum) or they have an affinity for lead or vise versa. Aluminum will dissolve several percentage points in lead.

...........FISH4BUGS [QUOTE=brimic]I commited one of the cardinal sins- I rendered w/ws in my casting pot....

Well I am surely going to burn in Reloader's Hell for my sins. I have been doing this for all my years of casting bullets. I have never had any problems whatsoever doing this. What is so bad about rendering w/w's in your casting pot as long as you clean it out after you do that? "

Well there is really nothing WRONG with rendering WW's or other scrap in your lead casting pot. It's just that it fouls it badly with junk and crud, plus it is just so dang small. Even if it's a 20 lb pot that's only 20 lbs from brim full to slap empty. Lets just say it's not very efficient, not wrong.

I'd hate to think how long using a 20lb pot would take to render 3-400 lbs of lead down.

I used to use a 2 burner Coleman gasoline camp stove and a large stainless steel salad bowl I liberated form the war department. She said I could have it so it wasn't an underhanded appropriation:D It worked like a champ too. I recall it was good for about 60 lbs or so.

Then enter the deep fat turkey fryers. A couple years ago I decided to go that route after hearing about several other casters using one.

http://www.fototime.com/4F0787827D40539/standard.jpg
It runs off propane and I use the 5 gallon bottles the BBQ uses. The cast iron dutch oven is a 6 qt and came from Harbor Freight. When it's 3/4 full of lead, you can barely pick it up. The burner melts WW fast. The large open top makes scooping out the clips a breeze.

The muffin tin on the left renders about 2lb ingots and the 6 holer on the right does about 5 pounders. You can pour maybe 60lbs of lead and still have a goodly supply in the pot to make quick melting of the next batch.

http://www.fototime.com/5BD9E698CF816FF/standard.jpg
These are what I store the ingots in outside. I got these at Lowes for $1.25 each w/lids. Supposed to be for storing shoes. They hold maybe 40-50 pounds of ingots. There were 17 of'em and I used them all in about 5 hours total work time, and that included beer breaks.

I was wandering around a Big Lots store while getting tires rotated a couple weeks ago and they had some plastic containers w/lids about the same size and of even heavier construction for 99 cents each so I got 25 of those for my pure lead.

http://www.fototime.com/EFCE2C499BA9C3B/standard.jpg
I got'em to use for this stack of lead sheilding bricks when I render them down. I've used 6- 8 of these bricks since the photo was taken. There used to be 76 of'em at 24 and 32 lbs apiece so there is still about 1600 lbs. And if you get stuff of this size, you're not going to get them into a 20 lb pot.

So it's not wrong to use your casting pot if that's all a person had to use. It's just that there are better, more efficient, faster methods without fouling up the casting pot.

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

[keeper89]

Buckshot, you are on the money again in regards to the turkey fryer setup. I melted ww in my old pots for years until I smartened up. Now I can put CLEAN ingots into my bottom pour in the basement and cast to my heart's content without upsetting the chief with that funky ww stench filling up the cellar! Easier to provide for the common defense if you have a little of that domestic tranquility!

[Linstrum]

Hi, there, brimic! Yup, I’d go along with what you saw with your yellow-orange metal “slurpie”. Buckshot pretty much answered your question about zinc and lead mixing. The two metals obviously mix because when the zinc gets into lead it messes it up for casting purposes. The actual amount of zinc it takes to mess up its casting properties is very little, though. Here’s the story behind exactly how little zinc metal it takes to mess up lead. Around 165 years ago, a smart chemist working for a silversmithing company in England was trying to find a cheap way to recover sterling silver scrap that was contaminated with lead solder. He had noticed that when silversmiths added zinc to their lead-silver solder to harden it that the resulting alloy separated into two layers. So, being a good chemist he wanted to find out what was floating on the top and he took it to a precious metals assayer. The assayer cupellated the mix and found out that the metal floating on top was silver and zinc. What surprised them about the floating metal was that there was no lead in it at all! None! The floating stuff was pure “brass of silver”, or silver-zinc alloy. They also discovered that getting the zinc out of the silver was easy by just heating it because zinc boils away at red heat. The guy’s name was Alexander Parkes, and until about 1920 the Parkes Process was the way that all silver was purified by precious metals smelters the world over, as well as both the British Royal Mint and the United States Mint. The Parkes Process depends on the fact that zinc is only sparingly miscible with lead, and with the addition of even small amounts of copper, silver, or gold with zinc it becomes totally and completely insoluble in lead.

So, if you want to get the zinc out of lead, add a bit of type metal that you know contains copper and the zinc will alloy with the copper and float to the top where you could then skim it off in the dross! Or you could add gold and the zinc-gold alloy would drop out to the bottom, since gold is heavier than lead. Or you could heat the lead up red hot to boil the zinc. Zinc is in the same family of elements as cadmium and mercury and for all three of them, it doesn't take much heat to melt and make them boil to a gas (mercury is already there!). To help out you could blow air through the lead to oxidize the zinc, but at that temperature it would make huge amounts of poisonous lead fumes plus maybe overheat or burn out your lead pot.

[brimic]

Oh, crap.

I just looked up the boiling pint of zinc- it appears to be around 900.
Is the stuff really toxic? I use good ventillation, but I don't expect metals to be evaporating at any significant rate while casting.

[brimic]

OOPs, I got that wrong. 900 degrees C is the boiling point.

[Linstrum]

Hey, brimic, yeah, you are safe from zinc fumes at casting temperature. The boiling point of zinc at 900° C / 1652 ° F is bright red heat and you don't get close to that. When zinc boils the vapor ignites and burns with a beautiful bright blue flame and makes huge clouds of white smoke. When pure zinc metal is molten and it catches fire it burns pretty much like magnesium but not quite so bright. The intense blue color is quite pretty, actually.

A few times I turned the lights out with the electric boolit alloy melting pot running to see how hot it was with the automatic thermostat control turned up to where I used it. After my eyes had adjusted to the dark I could just barely make out the dimmest dull red heat in the lead, which means it was right around 850° F.