casting trouble. Pot? Alloy? Zinc?

[Piedmont]

I have been using some new range lead that I bought. At the end of the casting session before tonight's I noticed the top of my melt wasn't melting properly but the bottom pour spout allowed casting to still take place. I use a 22 lb. RCBS pot that is 9 years old and normally run it full out and re-add sprues and additional alloy to the top as I cast.

It was with some trepidation that I fired up the pot tonight. I was worried that maybe my pot was dieing (thermostat or heat element). It took a little longer than normal and I thought I wasn't going to get anything out of it but eventually I got a stream below. The top stayed hard. I was eventually able to push down through it to try to mix it.

The top stayed slushy/oatmealy which I have read on here may be zinc contamination. One other thing I should mention is I melted one wheel weight of 1.5-2 ounces that I found on one of my walks to the pot during the session before tonight. So I might have zinc contamination from that or from the range lead I bought. (Obviously I don't know that weight was zinc and didn't think it was or it never would have made it to the pot.) I should also mention that this is the one time in my 28 years of casting that I wish I had a pot thermometer. I don't know how hot my lead was, only that it was going full blast.

So tonight I ran 200-300 240 grain bullets. The bullets were good. I added a couple of pounds of wheel weight ingots and a couple of 20-1, thinking these known good alloys might dilute what was in the pot for the better. I also fished out perhaps 7 lbs. of "oatmeal" and drained my pot and tipped the last pound or so in the bottom away from the spout so I can easily get it out when it cools.

So what do you guys think? Do I have zinc contamination or do you think the pot is dieing? I think I read years ago in a Fouling Shot that I can readjust my thermostat by taking the knob off and reorienting it for more heat. What would be the smartest thing to try first? Refilling with known good alloy?

If this "oatmeal is contaminated lead should I just throw it out or can it be rehabilitated? I have read zinc contamination will not allow good bullets but I got good bullets tonight.

Suggestions are welcomed.

[detox]

Removing zinc (lumpy oatmeal). Zinc has a higher melting point 787.2°F (419.5°C) Lead has a lower melting point 621.5°F (327.5°C)

You need a casting thermometer. Melt down your aloy to about 650-700 degrees no higher. Then flux very well using pine sawdust. After fluxing skim everything off top that looks like lumpy oatmeal. Melt should be mirror clean afterwards.

[WHITETAIL]

Yes, it sounds like you have a zinc problem.
Do not mix it with anymore lead.
Let it harden and put it aside.:holysheep

[44man]

Could be zinc but I would not flux before skimming and keep it at 600* for that part.
You need a thermometer to check the pot. I have had several that cycled so slow when they got old, lead would freeze on top, not good when using a ladle. You can watch the temp to see how much it drops before you hear the pot turn back on. Thermostats are too close to heat and go bad.
I made a PID unit and it worked but failed after a while, they get hot and a huge heat sink didn't help. It costs so much to make another it is cheaper to buy a Lee pot. Lee has a remote thermostat not jammed against the pot.

[GP100man]

I cast for along time without a thermometer , but now would cast without it .

Oatmealish but good boolits sounds as if you were rite on the edge of spout freeze temp.

For my Lyman Mag20 that`s around 580-600 with my current alloy.

& a ??? . Did the oatmeal on top lessen as other alloys were added to the melt ???

[Sasquatch-1]

If you still have the skim try the muracid(SP) test. Couple of drops on the stuff you skimmed off and see if it foams, if it does it is probably contaminated. If not you really need to check the temp.

[Piedmont]

Oatmealish but good boolits sounds as if you were rite on the edge of spout freeze temp.

. Did the oatmeal on top lessen as other alloys were added to the melt ???
That is another odd thing about it. Usually the last thing in the pot to get hot enough to cast is the spout. These last two sessions the spout is hot enough to pour but it is as if the top of the melt is too cool. I can't answer the second part because I fished out some "oatmeal" along the way.

I have a cheap old Lee 10 lb. pot somewhere. Maybe I will find it and put some of the 'bad' alloy that I skimmed off into it and see if it miraculously becomes fluid. That will answer the heat question without having to buy a thermometer or muriatic acid.

[1bluehorse]

Make it easy on yourself for now and future use....buy a thermometer...you're "cookin" in the dark without one.

[leadman]

It is fairly easy to drill out the rivets that hold the sheet metal together and get at the thermostat. This is a bourbon bulb type t-stat so named after the guy that invented it. It has a bulb and capillery tube leading from the bottom of the pot to the switch at the rear left of the unit. You can easily jumper the contacts on the switch to see if it gets hot that way. DO NOT LEAVE IT JUMPERED OFTER TESTING. If it heats up fine you know it is the heat coil.
I had t-stat problems with my pot and RCBS sent me a new one for no charge! However it only lasted about 1 1/2 months so I called RCBS and they sent out another new one no charge.
The new t-stats are slightly different than the old and do not control the heat as well as the old ones. RCBS says the standard is 50 degrees from on to off.

I built a PID controller for mine for about $75.00 with parts off #-bay. Not that hard to do. I am thinking of building one for my lubersizer and found parts even cheaper for a total of about $50.00.

Easiest way to rule out zinc would be to put it in your Lee pot and watch it melt or use the acid. As a rough (very) way to check temperature is to add a small chunk of candle wax on top of the hot alloy. If temp is over about 600 degrees it tends to self ignite. Not all candle wax is the same but this is probably within 40 degrees or so. At 700 degrees all of the waxes I use self-ignite.

[Piedmont]

Thank you all for your input. Anything electrical is beyond me, even simple stuff.

I just finished trying to cook the slush in my Lee 10 pound pot. It stayed ****. Only about 1/4 pound of the 3 or so pounds I cooked came out of solution. I threw all the slush stuff away. This is probably the best result as it implies my RCBS pot is still good.

I do have seven pounds of good ingots and a coffee can full of sprues and a few cull bullets that I would like to use. The bullets from this pot were good. I am under the impression the sprues, culls, and ingots I got when draining it will be uncontaminated, since none of it was slushy. Am I wrong? I would like to cast some boolits from it and maybe will use the Lee pot to do so when I can figure out what I want to cast and thereby eliminate the RCBS pot as a variable.

It would be a good idea to pick up a thermometer the next time I order reloading gear.