Is your lead ever TOO soft?

[sagacious]

Here is anoter question to throw out there...

What kind of lead alloy is shiny, but floats to the top of the pot, kind of thick, almost exactly like butter? Stirring will not mix it back in, and it does not pour or form, so I end up skimming it off. Once it hardens, it looks just like regular lead. I think it came from a batch of lead wire...

-TH

That's an excellent question, and the answer can get sort of complicated, because lead from an unknown source might have just about anything in it. However, let me answer your question as simple and practical as possible.

The floaty, shiny sludge you're seeing is commonly encountered when remelting scrap lead ingots, and very often with ww lead ingots and battery lead. Lead wire is usually poured from reclaimed battery lead (that was supposed to have that gunk removed, but that doesn't always happen).

The 'impurities' in a lead alloy will migrate to the top, especially right after the batch of lead has just melted. You may notice this more often in a bottom pour, or anything that doesn't heat the lead really super hot. The tin component of the alloy will rise to the top and oxidize fairly quickly. Antimony (in hard lead alloys) doesn't actually like to mix with lead very much, and will form a frothy sludge. Any dirt particles that can be 'wetted' by lead will rise to the top and join the sludge party.

Plus, there's usually other stuff in scrap lead that you might not expect is in there. Some of this stuff can be a real pain. Very teeny-tiny amounts of aluminum, calcium, and copper will form oxides or intermetallic compounds with lead, and will float up into your sludge. Those impurities will decrease the 'fluidity' of lead, and prevent the lead from filling-out the mold cavities. Years ago, I had some lead that was comtaminated with a tiny amount of copper. Didn't want to pour well, and made for large shrinkage cavities.

Anyway, it's nice that stuff floats to the top, since it makes it easy to skim off. By skimming off the sludge, you'll remove much of the impurites. Then, by fluxing the metal, you'll remove most of anything else that might cause problems. (Note: by skimming off the sludge, you're also losing some of your good lead that's mixed up with the crud. Unless you suspect there might be a lot of really problematic impurities in your lead, fluxing alone usually removes the impurities without losing any lead.)

First, and do this outside, flux the melt with a small amount of paraffin wax. Say, about a marble-sized chunk for 10lbs of lead. It will melt, and smoke, and will eventually flame up. While it's melting, stir it into the lead, and scrape the sides of the pot. Stir it in good. Then skim off the black powdery gunk that remains, dispose of it safely, and start pouring. Some folks flux with sawdust (no, really, it works!), and it does a good job of binding to, and removing the impurities that really louse up the pourability of lead, plus its free. With sawdust, just go throught the same process as above. Commercial fluxes are also available that work great, and don't smoke.

Hope this helps. Good luck and be safe!

[Ogajiga]

Another way to release the useable metal from the floating sludge is keeping the skimmed off slag in a small cast iron sauce pot with a handle and a pour spout. Around 1/4 pot full, reheat the slag and when the residual lead liquifies and separates from the solids spray in some WD40 (wax would probably work too) as a fluxing/reduction agent with the POT OFF THE HEAT SOURCE. The pot will flame when put back on the heat source and when stirred the hard chunky solids will turn to blackish powder releasing even more lead melt. This process is called reduction when heated carbon combines with the metal oxides to free up some of the metal. The metal melt can then be poured off into ingots and the powder residue can be strained to separate any remaining metal bits which can be saved and processed with the next batch of slag. Its surprising how much useable metal can be separated from the waste slag this way. The 1 qt. or so flat bottom cast iron cooking pots with spout and handle are actually not that hard to find at garage sales or thrift shops.

[fitterdavis1942]

hey oldwillie 65 i've been trying to get ahold of you i left you a couple of pm's. give me a holler if you get a chance. jeffdavis1942@msn.com jeff from hesperia

[turkeylegs1246]

Hmmm...soft lead has a higher melting temperature than ww lead? I'm using medical weights purchased from salvaged metal yard. It is pretty soft but I am having problems getting it to fill the cavities of slab molds. Air pockets form as the lead cools. I'm using a Lee 700 watt 20 lb bottom pour pot. I'm preheating my mold by pacing it on the lead pot and pouring baits w/o insert prior to pouring slabs. I've thought that the lead just isn't getting hot enough. I've ordered a thermometer to determine what the temperature of the lead reaches. The rheostat on my lead pot is maxed out. I can't get good flow of lead into the mold.

Am I correct in assuming that if I mix ww lead with my "soft" lead that the melting temperature will be reduced and the pouring/flow characteristics will be improved?

Edited April 7, 2008 by turkeylegs1246

[Ogajiga]

My observation is that the antimony and other metals in wheel weights mixed into soft lead will generally cause quicker melt freeze. Pure soft lead appears to be the easiest pour and any other metal added in will make it tougher. Who knows though, wheel weight lead added to your "medical weight" lead might pour better in your slab mold.

[sagacious]

...

I'm using medical weights purchased from salvaged metal yard. It is pretty soft but I am having problems getting it to fill the cavities of slab molds. Air pockets form as the lead cools. ...

As Hawnjigs alluded to, it's difficult to know the characteristics of an unknown alloy-- and thus it's difficult to suggest a specific remedy with any guarantee of success. "Medical weight lead" could mean almost anything. Probably best to not buy any more of it.

Yes, pure lead melts at a higher temp than ww lead. As far as I know, all alloys melt at a lower temp than the average melting temp of their component metals.

I've seen the shrinkage cavities you refer to many times. That problem is occasionally found in batches of scrap lead. Very low amounts of some contaminants in the lead seem to cause this. Usually it becomes a more noticeable and problematic factor in jigs over a couple ounces. While it's not what you might have expected, one remedy I can suggest-- with fair confidence-- is that you should NOT max out the temp when pouring that batch of lead. Higher temps with that lead alloy will almost surely equal larger shrinkage cavities, and higher temps will only make the problem worse. The solution is to preheat your mold adequately (do not overheat the mold), and pour at as low a temp as possible. While its commonly believed you need to keep everything as hot as possible, if you're experiencing shrinkage cavities, go lower temp. Also, I have found that with some lead alloys that have shrinkage cavity problems, too high a pouring temp promotes an oxide surface film, or 'skin', and that can cause flow problems. I know some of this may sound crazy, but try it and let me know how it goes.

Am I correct in assuming that if I mix ww lead with my "soft" lead that the melting temperature will be reduced and the pouring/flow characteristics will be improved?

Melting temp and fluidity are two seperate and very different things. It is a mistake to believe that, generally, one alloy with a lower melting temp will pour easier than another with a higher temp. Even so, adding ww lead to your mix may help. Let me explain...

The rub is this: 'Pure' lead melts at one temperature, and also freezes at that same one temp. Most lead alloys don't melt at one temp, they become sort of "pasty" and soft, as the various alloyed components of the lead each individually begin to melt. So, ww lead will start to thicken up and get sludgy as it nears it's freezing temp. It's more important to keep ww lead at the right temp, so it's not sludgy when you pour it. Make sense? If you don't have good temp control with ww lead, you won't get good pours, and that's one reason why those new to pouring lead get the advice to use 'pure' (read: soft) lead.

However, the alloy components in ww lead (that start to freeze-out of the melt near it's freezing temp) can reduce or eliminate the shrinkage cavity problem, by negating the effect of the contaminant(s), by promoting quicker melt freeze. Slower melt freeze with your batch of lead means a larger shrinkage cavity. Faster melt freeze means less shrinkage, and that's what you want. Mixing your "medical weight lead" 50/50 with ww lead might just fix your problem right away. Also, you should be fluxing your lead thoroughly before you pour, because that can help fix your shrinkage cavity problem.

It sounds like you may also have a constriction in your pour spout. Make sure that's clean and unblocked. Or, if you can't get good lead flow into the mold with known good lead, the mold may need to be vented, or the gate opened slightly.

Hope this helps, good luck.

Edited April 7, 2008 by sagacious

[Ogajiga]

I didn't realize until "Sagacious" pointed out that its possible to overheat the melt. Doing some online research, I found that liquid lead will expand with heat, which means that the hotter the melt the more it will contract when it solidifies. Also found that antimony contracts only 1/5 as much as lead on solidification so indeed its presence in a lead alloy could improve fill out. My experience is though that incomplete fill out problems caused by contaminants are best remedied by switching to softer lead.

[turkeylegs1246]

I've seen the shrinkage cavities you refer to many times. That problem is occasionally found in batches of scrap lead. Very low amounts of some contaminants in the lead seem to cause this. Usually it becomes a more noticeable and problematic factor in jigs over a couple ounces. While it's not what you might have expected, one remedy I can suggest-- with fair confidence-- is that you should NOT max out the temp when pouring that batch of lead. Higher temps with that lead alloy will almost surely equal larger shrinkage cavities, and higher temps will only make the problem worse. The solution is to preheat your mold adequately (do not overheat the mold), and pour at as low a temp as possible. While its commonly believed you need to keep everything as hot as possible, if you're experiencing shrinkage cavities, go lower temp

.

So, how does one preheat the mold adequately w/o overheating and ruining the mold? I've always placed the mold on top of my leadpot after I've made a few castings w/o wire inserts. I am thinking that that may not be enough of a preheat. I've experienced that after I put the wire insert into the mold that I get better pours if I replace the mold on top of the leadpot to allow the wire inserts to heat up also. I've read that some casters reccommend placing their mold on top of an electric hot plate to preheat the mold. I'm thinking that the hotter the preheat of the mold that the better the lead flow inside the mold will be. The hotter the mold, the slower the lead will solidify. That should help eliminate shrinkage. One of my slab molds is two cavities. I find that if I pour the cavity w/o inserts first and then fill the other cavity with the insert that I get better slabs. Of course that is time consuming. If I go lower temperature it seems to me that preheating the mold is even more crucial to obtain satisfactory results.

[sagacious]

So, how does one preheat the mold adequately w/o overheating and ruining the mold? I've always placed the mold on top of my leadpot after I've made a few castings w/o wire inserts. I am thinking that that may not be enough of a preheat.

Adequate means enough, but not too much. The process your describe above seems adequate to preheat the mold. Pouring without inserts is the best method-- do not risk overheating the mold by using another preheat method.

I've experienced that after I put the wire insert into the mold that I get better pours if I replace the mold on top of the leadpot to allow the wire inserts to heat up also.

Correct. This is common practice to ensure good pours. A much quicker method is to use a hotplate, for example, to warm up several inserts before placing them in your mold. Warm them adequately, which in this case means just a little hotter than you'd want to touch with your fingers....... but not red hot! As you pour, add a few more inserts to the hotplate to warm up. The culprit here is the wire insert, not the mold, so attack that as the problem. By preheating the inserts, you can pour as soon as you place the inserts, and this allows the mold to retain more of the heat it acquires from pouring. You'll get better pours, and more pours per hour.

I've read that some casters reccommend placing their mold on top of an electric hot plate to preheat the mold. I'm thinking that the hotter the preheat of the mold that the better the lead flow inside the mold will be. The hotter the mold, the slower the lead will solidify. That should help eliminate shrinkage.

No, not correct. The hotter the mold, and the hotter the lead, the more shrinkage you'll get. Hard to get around that one, it's just one of the physical properties of lead. Yes, the lead will flow better, but it will shrink more. If your batch of "medical weight lead" has both serious shrinkage cavity problems, and serious fluidity problems, you may have to just struggle with it until you use it up. Don't buy any more of it.

One of my slab molds is two cavities. I find that if I pour the cavity w/o inserts first and then fill the other cavity with the insert that I get better slabs. Of course that is time consuming. If I go lower temperature it seems to me that preheating the mold is even more crucial to obtain satisfactory results.

This is a common symptom of inconsistent or inadequate mold temperature. Your mold is cooling down too much between pours. There's a range you're looking for-- too hot is not good, and too cold is no better. As you pour the first cavity, a wave of heat travels along the mold and re-heats the second cavity.

This problem is also solved by pre-heating your inserts. This will eliminate your down time spent reheating the mold+inserts and keep your mold temp much more consistent, and it will increase production. With reduced down time, your mold cavities will stay at the right temp, and you should easily be able to pour both cavities. If you're pouring fast with a mold that drops large jigs, it's much more common to have the mold get too hot, and have to occasionally pause to let it cool down a bit.

I pour a lot of 6.5oz slab jigs. They have a custom full-length insert made from 0.076" stainless wire. I exclusively use ww lead. Believe it or don't, but I don't ever get incomplete pours. The techniques detailed above do indeed work very well. TU Forum Home - Luremakers Photo Gallery - finished product- foiled/painted jigs

TU Forum Home - Luremakers Photo Gallery - foiled jigs

Whew! This has been a lot of typing , so I hope this information helps provide the solution to your shrinkage cavity and fill-out problems.

Be safe, and best of luck!

[turkeylegs1246]

sagacious

Well thank you! I took your advice and reduced the heat to my lead pot. I started out struggling to get my mold warm enough to cast my slabs. I got incomplete fills and wrinkles that I returned to the pot. Things just didn't go the way I had hoped following your advice. Then it dawned on me that by returning my scrap to the pot that I was cooling the melt. So I stopped that. My pours continued to improve gradually. Once the melt managed to get my mold to the right temperature, the cavities filled better and better. The shrinkage that I have referenced disappeared as did the wrinkles and incomplete fills. When that happened I poured over 20 baits that were, in my eyes, great! I stopped there! I am confident that that will happen again and again.

I noticed while preheating the mold that lead was flowing into the wire cavities. That is something that likely indicates good flow in the mold. The shrinkage problem also disappeared during preheating the mold. I've poured a lot of baits with lead that was too hot. And even though those baits weren't perfect, they painted up nicely and caught fish. I'm looking forward to getting these finished as well. They may not catch any more fish than the others but they are going to be easier on my eyes! I'm grateful.

Buck Perry, whom many refer to as the father of stucture fishing, had a saying that, "Knowledge is the key to success." Your replies, I'm certain have greatly expanded my knowledge and hopefully my success.

Many thanks! I appreciate the schooling!

Edited April 10, 2008 by turkeylegs1246

[sagacious]

sagacious

Well thank you! I took your advice and reduced the heat to my lead pot. I started out struggling to get my mold warm enough to cast my slabs. I got incomplete fills and wrinkles that I returned to the pot. Things just didn't go the way I had hoped following your advice. Then it dawned on me that by returning my scrap to the pot that I was cooling the melt. So I stopped that. My pours continued to improve gradually. Once the melt managed to get my mold to the right temperature, the cavities filled better and better. The shrinkage that I have referenced disappeared as did the wrinkles and incomplete fills. When that happened I poured over 20 baits that were, in my eyes, great! I stopped there! I am confident that that will happen again and again.

Fantastic! I have no doubt that your pours will go better and better. That clears up another concern-- your lead seems to be OK, it was just the overheating of the melt that caused the shrinkage cavities. Now you know how to avoid that, and still get great pours.

I noticed while preheating the mold that lead was flowing into the wire cavities. That is something that likely indicates good flow in the mold. The shrinkage problem also disappeared during preheating the mold.

Correct-a-mundo. Continue preheating by pouring without inserts until the lead will fill-out the wire insert recesses. When that happens, you know you're set to pour with inserts.

I've poured a lot of baits with lead that was too hot. And even though those baits weren't perfect, they painted up nicely and caught fish. I'm looking forward to getting these finished as well. They may not catch any more fish than the others but they are going to be easier on my eyes! I'm grateful.

Buck Perry, whom many refer to as the father of stucture fishing, had a saying that, "Knowledge is the key to success." Your replies, I'm certain have greatly expanded my knowledge and hopefully my success.

Many thanks! I appreciate the schooling!

Wise words indeed. Someone told me today that, "Practice makes experience, and experience makes knowledge." And as we all know, knowledge is it's own reward. The experience and knowledge you gained are just another feather in your cap-- so snap your suspenders and congratulate yourself on your success!

All of this, hopefully, will help you avoid some hassles and frustration during your lead pouring, and make it easier for you to trouble-shoot problems faster. And you're right, the fish may not care, but it's obvious that you-- we all-- take pride in our handiwork and want to be confident with the quality of our work, and confidence = fish.

Sometimes you have to go against what you might expect-- like, say, reducing your melt temp-- to solve a vexing problem. And that's part of the subtleties of lead pouring that moves you further toward mastery of your craft.

Good luck, and good fishing!

[Saugerman]

Heating your hooks and wire forms are very important,a very handy way of doing this if you don't have a hot plate, is to use a crock pot. My wife recently broke the bowl to her crock pot,I latched on to the bottom part of the pot,where the pot heats up from,basicly just a hot plate ,and it works great to heat up you hooks or wire forms. I just set the temperature to low, and you can handle hooks or forms with your hands, and it's still worm enough ,not to draw down the temperature of yor lead.

Most every one has one of these setting around,some where.

[sim]

I have my painting oven near my lead pot - what temp range are we looking at to pre-heat the inserts?

Low on a crock pot seems to be around 225F in my head.

[sim]

I have my painting oven near my lead pot - what temp range are we looking at to pre-heat the inserts?

Low on a crock pot seems to be around 225F in my head.

I answered my own question last nite - turned on my heatgun - on medium, one setting below where I normally paint with - held the wire/hook form in front of it for 5 or so seconds, put it in my spinnerbait mold that had been setting on top of the lead pot...

had the first perfect pour I've seen in a long time.

Sometimes its the simple thing - I had _never_ warmed up the hooks/wire before and would fight to get a good pour - 1 out of 5 might be "good enough".

Thank you tackleunderground, you saved the day!