Frustrated with zinc! Smelting help, please!

[famdoc2892]

OK, guys, I'm desperate for some good ideas! Smelting out wheel weights, and my last 3 batches have turned to oatmeal. After the first batch, I emptied my pot, scraped out all the residue and started over with wheel weights that I tested individually with side cutters. When the second batch went sideways, I cooled the pot, emptied it again and scraped it out. Thinking I had picked up a few weights that I hadn't checked, I pinched every single weight that went into the third batch, but no dice. Still turned to mush about halfway into the melt.

What gives? I'm using a Dutch oven that yields 40-50 pounds when filled, and tested every single weight this last time. Any thoughts on how this is happening? Could there be enough zinc left on the slotted spoon/stirring stick/pot to poison a 20-lb pot? Is there anything else that would resemble zinc contamination, too hot, too cold, adding too much cold lead at a time, etc? I appreciate any ideas.

[meece]

Pot those few deg too cold and adding too much solid lead oatmeals my pot for a short time. i just crank the heat and it goes back to to liquid after a while. Also remember that alloyed lead with tin and antinomy in it oatmeals for a few seconds before melting pure lead just melts.
If you get the temp just right the lead will be molten and the zinc floats to the surface anyway.

[RickinTN]

The oatmeal you're seeing is probably the antimony oxidizing out of your mix. Have you tried fluxing/reducing it back into the melt properly? Put an inch or so of pine pet bedding or some type of dry wood chips on top of the mix, oatmeal and all. Light the chips and let them burn. When the flame dies down let the embers smolder on top of the mix for 5 minutes or a little longer. This will reduce the oxidized metal back into the mix. Skim the ashes off the top.
Good Luck,
Rick

[220swiftfn]

It sounds like you're describing the "slush stage"..... Question, does it *really* look like oatmeal, or does it look more like a silver Wendy's "Frosty"???

Dan

[bangerjim]

You are not seeing massive Zn invasions! Your temps are at the "slush" stage as said above.

Just remelt at a slightly hotter temp using sawdust and wax to flux/reduce (3x) the Sn/Sb back in. Do not throw you earlier melts out! they are all still good.

it would take a MASSIVE amount of Zn to create what you are describing! I have intensionally contaminated 10# of pure with 1,2,3,4,5% Zn and saw very little problems with casting. At 4-5% you need a bit more tin to lower the surface tension which is increased by the Zn.

But do not fear the zinc monster! Many on here bemoan one zinker WW in 100# of lead and "throw the whole pot out". No big whoop.

If you are paranoid about Zn contamination, you can remove it (and Sn and Sb) by using sulfur (from plant store) or copper sulfate (from Lowe's as root killer in plumbing section). Search the threads on here for how to do it. Covered in great detail many times in the past.

Happy re-melting!

banger

[badbob454]

agreed turn up the heat look for floaters and scoop them out .... zinc wont melt easily into a pot.. they float to the top so you can scoop them out , dont give up ...

[famdoc2892]

In answer to the previous question, I've got the "silver Wendy's frosty" look. Yes, I've kept the earlier melts, I'll keep working on them, and thanks for the encouragement!

[Outer Rondacker]

I might not have many posts but I do have to agree with all that has been said. Crank the heat. I use a rocket stove to melt my lead. Its free and really puts out the heat. Plus I just like that kinda stuff. If you lack the heat look into a small home built rocket stove from bricks using sticks from around the yard to fuel it. Good luck and please let us know (me) how it turns out.

[famdoc2892]

I appreciate the suggestion. I wasn't familiar with rocket stoves, and enjoyed looking up info on them. Looks like I've got another project on my list!

[JonB_in_Glencoe]

what's the Temp ?
if you're not using a thermometer, it's time to start.
it sure sounds like you don't have enough heat.
Jon

[famdoc2892]

That's what I'm thinking, I'm using a Wal-Mart special turkey fryer, but disappointed with the burner performance. I bypassed the safety timer, but now wondering if I'm using the right orifice. My burner has none of that "jet" sound while burning, and can't keep a blue flame unless I feed extra air into the back side of the venturi using a valved nozzle from my air compressor... I do have a thermometer, but when I tested before and it stopped around 480 degrees, I figured it was broken and haven't tried again.

[JonB_in_Glencoe]

OK...Good info.
Now, what about wind ?
Is there any wind blowing on your flame.
then it's time to build a wind shield.

[jsizemore]

Your probably using a 4 quart dutch oven to end with 40-50 lbs of melt. Your regulator is probably silver colored and is 5psi. With the cooler weather you can get by with that setup if you use a wind shield and lid. If you go to a red/10psi regulator you can melt all you want without the wind shield as long as it ain't trying to blow hard. Throw a little wax or parafin on top of the slush, light it, and the slush will go away.

[famdoc2892]

Good info, my friends! It was windy yesterday afternoon, and my efforts at a wind screen have been halfhearted. I am using the silver 5 psi regulator, but I have others I could plumb in. I'd considered several of these options, but appreciate the push in the right direction!

[jsizemore]

I use the sheetmetal jacket from a hot water heater cut off to fit from the ground to an inch shy of the top of my pot. I use the sheetmetal top of the h/w heater for a lid. The holes for the plumbing pipes allow inspection ports to keep an eye on the melt and hold the thermometer. I split the sheetmetal along the thermostat/element covers and use a small pair of vise grips to hold it together when in use. Easily doubles the amount of lead I can smelt on a tank. It costs me about 1.3 cents/lb for gas.

[famdoc2892]

Wow! Had no idea I was losing that much in efficiency! I'm cheap by nature, so the windscreen just moved up the list of things to do before I smelt again. I'll start scrounging the materials pile with a will!

[220swiftfn]

In answer to the previous question, I've got the "silver Wendy's frosty" look. Yes, I've kept the earlier melts, I'll keep working on them, and thanks for the encouragement!

Yep, a little more heat and you'll be golden....


Dan

[220swiftfn]

That's what I'm thinking, I'm using a Wal-Mart special turkey fryer, but disappointed with the burner performance. I bypassed the safety timer, but now wondering if I'm using the right orifice. My burner has none of that "jet" sound while burning, and can't keep a blue flame unless I feed extra air into the back side of the venturi using a valved nozzle from my air compressor... I do have a thermometer, but when I tested before and it stopped around 480 degrees, I figured it was broken and haven't tried again.

It might be the regulator choking it, you want the high pressure regulator (The red one IIRC).....


Dan

[leadman]

If you have some pool acid you can confirm that you do or do not have zinc in your mix. Even on the zinc wheel weights the pool acid will foam and turn the area where it is at black. Works on boolits and ingots also. The copper sulfate makes a decent flux and the side benefit of it is it hardens your alloy, even if you have no zinc in it. I use it frequently.
From what you are describing though the others nailed your problem.

[famdoc2892]

Smelting "range report"- Undying gratitude, my friends! I am humbled and honored to be counted a member of this great casting fraternity. Your diagnosis was correct, and your tips paid off in spades! I used a wind screen made of aluminum foil and thick layers of sawdust for both top covers and redux flux. Also lit the sawdust as it charred, a practice I'd not used before. Propane consumption and time to melt reduced to 1/4-1/3 of previous levels, resulting in almost 120 pounds of ingots produced in about 3.5 hours from start to clean-up! No problems getting antimony reduced back into the melt, and clean, clear lead that poured like water. Many thanks for sharing your expertise!

[jsizemore]

Your efficency will improve with experience and tweaking your setup. Increase your ingot molds and time will drop dramatically.

[ubetcha]

I might not have many posts but I do have to agree with all that has been said. Crank the heat. I use a rocket stove to melt my lead. Its free and really puts out the heat. Plus I just like that kinda stuff. If you lack the heat look into a small home built rocket stove from bricks using sticks from around the yard to fuel it. Good luck and please let us know (me) how it turns out.

Not to change the subject, but looked into rocket stoves since you had mentioned it. Very, Very interesting. One question though, how is the temp regulated?. Just by the amount of fuel added?. I can see the lead getting pretty hot using this and I don't what to burn off some tin

[famdoc2892]

You guessed it, the temp is regulated by the feeding of fuel to the fire. Rocket stoves have the advantage of improved combustion, only heating the end of the wood to be burned, so the amount of fuel fed into the chamber determines the vigor of the reaction and the heat passed up the chimney to the pot.

[fredj338]

If you are sorting, zinc in the mix should not be the issue. Maybe your just not getting enough heat going prior to fluxing?

[famdoc2892]

Agreed, that's what the previous posters suggested, and following their advice by adding a wind screen and a thick top layer of sawdust which is lit and allowed to burn paid big dividends in efficiency!

[lwknight]

By all means, get a casting thermometer. Would you let your teenager drive a car without a speedometer?
Same thing.