sdsaw Posted June 27, 2009 Report Share Posted June 27, 2009 Forgive me if this is common knowledge around here. I just discovered this and had to share! This has been plaguing me on certain leadheads from the beginning of this pouring addiction. On some of my pours, I would get a dent or crater on the flat side of the Style "9" Shad Head out of a Do-it mold. Also in the bottom of the eye sockets of some molds. Never could figure out why. Assumed that it was a lead temperature issue because I was using a small "Hot Pot" melter to heat and pour my heads(lead not getting hot enough) Example of a typical dent Recently got a thermostatically controlled Lee Magnum Melter so the lead should get plenty hot now Did some "warm up" pours in my mold and got this result. Did several more "practice" pours and kept getting the same results even after the mold was good and hot I always coat my molds with candle soot. Many times by reapplying more soot, it will cure pouring issues. Heavily coated cavity I figure the more the better, right? Not so! Just as an experiment, I decided to wipe the soot from the cavity ...And on the next pour, got this If you will notice, the lead surface is not real smooth. In fact you can clearly see the layers as the lead was poured in, but the crater was gone! There's probably a compromise between "just enough soot" and "too much soot" If you ever have this issue while pouring, try a little wiping of the cavity. Scott Quote Link to comment Share on other sites More sharing options...
JSC Posted June 27, 2009 Report Share Posted June 27, 2009 I belive it is in the hardness of the metal ... add some soft to what you are using and I think that will help. I know some of the others will add to this. JSC Quote Link to comment Share on other sites More sharing options...
cadman Posted June 28, 2009 Report Share Posted June 28, 2009 sdsaw, just my worth to your dilemma. I don't believe that too much soot is the problem. I will have to agree with JSC. It is lead composition. Too hard of lead and you will have problems, I have never heard of anyone having problems with really pure soft lead. However your experiment is very interesting, maybe others have more insight on this. Quote Link to comment Share on other sites More sharing options...
sagacious Posted June 28, 2009 Report Share Posted June 28, 2009 (edited) Scott, I have to respectfully correct your interpretation of the cause of the shrinkage cavities and "dents" in the photos posted above. The cause is well-known to be excessive lead temperature, and not deficient lead temp, or excessive soot. In the cases where you experienced shrinkage cavities, your lead was way too hot. This is very common, but commonly misunderstood. Hotter is definitely not always better, and softer is likewise not always better. The more you heat lead, the more it expands. That's why lead ingots sink in molten lead. The more you (over)heat it, the more it will shrink upon cooling. Shrinkage voids and "dents" result. Your post gives more cause to believe this is the reason. The second photo shows an eyelet recess that is filled with lead around the hook eye. That's another definite and diagnostic sign of quite excessive pouring temperature. As the photos show, there's no question the second jighead was poured at a higher temp than the first. Based on the size of the shrinkage cavity, the lead was really too hot. That you believed insufficient temp was the culprit is also an indication of even more overheating in the second photo. As you see, more heat = more shrinkage. Your third photo shows indications that after you removed the soot, your lead temp or mold temp were too low-- the solidification lines on the jighead are evidence of this. I can tell just from the photos that you're using fairly soft lead. The slight shrinkage cracks surrounding the shrinkage cavity in the first photo are a clear indication of this. Contrary to popular belief, "pure" or soft lead is much more likely to develop shrinkage cavities than is a more alloyed lead, such as wheel weights. Heavily alloyed lead, such as type metal, shrinks much less when overheated than soft lead, and may not show any shrinkage at all. Mold cavity volume is also a significant factor in shrinkage voids cause by excessive heat. The larger the volume of lead, the more shrinkage will show in the castings. A very small jighead may show no visible shrinkage cavity when poured from overheated lead, whereas the large 2lb "salmon weights" we use here on the West Coast show enormous shrinkage cavities when poured from soft lead that's overheated. The way to solve it is to either, 1) get a thermometer and reduce the pouring temp, and keep the lead at a constant temp that doesn't product dents with your lead alloy. Your pics show evidence of wild fluctuations in mold temp or lead temp, and likely both. Or, 2) add some wheel weight lead to your soft lead, say 50/50. This will further minimizing the effects of temp variations on the quality of your pours. Soot from smoking the mold also helps to reduce to effects of temp variation. Don't give up on smoking the mold cavities just yet. Hope this helps-- just thought you should know. Good luck and be safe! sagacious Edited June 28, 2009 by sagacious spelling correction Quote Link to comment Share on other sites More sharing options...
sdsaw Posted June 29, 2009 Author Report Share Posted June 29, 2009 Guys, Thank you for your input to this post. The reason that I put up this up was because the results of my experiment (wiping off some of the soot) was so immediate and drastic that I wanted to share it and possibly help someone else out with a similar issue. sagacious wrote: The cause is well-known to be excessive lead temperature, and not deficient lead temp, or excessive soot. In the cases where you experienced shrinkage cavities, your lead was way too hot. This is very common, but commonly misunderstood. Hotter is definitely not always better, and softer is likewise not always better. The more you heat lead, the more it expands. That's why lead ingots sink in molten lead. The more you (over)heat it, the more it will shrink upon cooling. Shrinkage voids and "dents" result. -I won't or can't disagree with this fact. Very good info As the photos show, there's no question the second jighead was poured at a higher temp than the first. Based on the size of the shrinkage cavity, the lead was really too hot. That you believed insufficient temp was the culprit is also an indication of even more overheating -The first photo was from a different mold(smaller size) and was poured at a different time but shows the ongoing issue that arises now and then. The second photo shows an exaggerated crater that is unusually deep. Your third photo shows indications that after you removed the soot, your lead temp or mold temp were too low-- the solidification lines on the jighead are evidence of this. -Well maybe, but this was poured within a few minutes of each other without changing the thermostat setting. I can tell just from the photos that you're using fairly soft lead. The slight shrinkage cracks surrounding the shrinkage cavity in the first photo are a clear indication of this. Contrary to popular belief, "pure" or soft lead is much more likely to develop shrinkage cavities than is a more alloyed lead, such as wheel weights. Heavily alloyed lead, such as type metal, shrinks much less when overheated than soft lead, and may not show any shrinkage at all. -You have a very sharp eye, and yes, the lead is of the soft variety(spent bullets) ... and more good info. The way to solve it is to either, 1) get a thermometer and reduce the pouring temp, and keep the lead at a constant temp that doesn't product dents with your lead alloy. -Got an infrared one on order -Do you have some temperature ranges that I should be maintaining? Your pics show evidence of wild fluctuations in mold temp or lead temp, and likely both. Or, 2) add some wheel weight lead to your soft lead, say 50/50. This will further minimizing the effects of temp variations on the quality of your pours. -That's good to know because I have much more ww lead than soft lead and that will help stretch my supply. Soot from smoking the mold also helps to reduce to effects of temp variation. Don't give up on smoking the mold cavities just yet. -I'm not giving up on the soot! It's made a difference for the better too many times! Learned a bunch. Thanks! Quote Link to comment Share on other sites More sharing options...
sagacious Posted June 29, 2009 Report Share Posted June 29, 2009 Scott, I have to hand it to you, your photos made the diagnosis simple. It's not common to have a pouring problem documented and explained so clearly. It makes identifying the fix much simpler and more accurate. The remedies I outlined will solve your problem. I purposely didn't suggest a temp range. There are many factors that can affect the temp range considerably, such as your specific alloy (soft lead to ww lead ratio), the mold size and cavity volume, the pour rate, whether you remelt the cut-off sprues immediately, etc, etc. The main goal is to find the temp range for your circumstances that doesn't produce dents or difficult pours, and then maintain a steady pouring rate. I've seen these shrinkage cavities many times. Occasionally it's tough to avoid entirely on large-volume castings, and especially so once the mold gets a bit too hot. Diagnosing this problem on smaller jigheads is fairly straightforward. The things to remember from this is that hotter isn't always better, and that softer isn't always better. I pour all jigs above 1/2oz from straight wheel-weight lead, and without any difficulty or problems at all. You may wish to give that a try and see if it works for your application. WW lead takes rocky-reef abuse much better than soft lead. Learning is what makes the difference here. Some folks struggle with the same problems for years without seeking a solution, or are so stubborn that they simply refuse to change their ways. Congrats on being flexible enough to accept and incorporate new knowledge into your pouring routine. More questions, just ask. Good luck and stay safe! Quote Link to comment Share on other sites More sharing options...
JSC Posted June 29, 2009 Report Share Posted June 29, 2009 Saga .. Glad you came in on this one. I do have one question .... Will harder Lead shrink more than the softer?? I have noticed this more on big molds when they get hot. (which you brought out). Good Thread Thanx JSC Quote Link to comment Share on other sites More sharing options...
sagacious Posted June 29, 2009 Report Share Posted June 29, 2009 Saga .. Glad you came in on this one.I do have one question .... Will harder Lead shrink more than the softer?? I have noticed this more on big molds when they get hot. (which you brought out). Good Thread Thanx JSC Harder lead will definitely shrink less than soft lead. With some very hard lead alloys there is no shrinkage at all, and in fact may expand slightly upon cooling. This is due to the growth of crystalline alloy compounds within the solidifying lead. Soft "pure" lead doesn't do that, and is thereby more affected by the volumetric changes caused by heating and cooling. When you pour overheated soft lead into a mold, you're actually pouring in less lead (by weight) than you think. When it cools, it shrinks and you may get a dent in your casting. The casting with the dent will always weigh less, obviously, than a perfect casting-- even though you poured the cavity completely full of molten lead. You poured in less lead because it increased in volume while it was overheated, and shrunk when it cooled. Harder lead alloys are usually less affected by this transition from the molten state to the solid. Even if the lead isn't overheated while pouring, the measured shrinkage of softer lead alloys is always greater than for harder lead alloys. You may notice this effect when soft lead castings fall free from a mold cavity easily, while hard lead castings sometimes stick a little in the same mold. It is common for some folks to pour hard lead (like ww lead) at a considerably higher temp than is optimal. The usual cause of this is a lack of proper fluxing of the lead. Once ww lead is fluxed, it does not require overheating to get perfect castings in most applications. The best practice is to always pour only as hot as needed, but no hotter than necessary. The best practice is to always pour only as hot as needed, but no hotter than necessary. As a general rule, the softer the lead and the larger the cavity volume, the more shrinkage that will occur, and especially if the lead is overheated. If you're pouring in the right temp range for your application, you may not notice any shrinkage at all. Hope this helps, good luck! Quote Link to comment Share on other sites More sharing options...
cadman Posted June 30, 2009 Report Share Posted June 30, 2009 (edited) Sagacious, You hit it dead on, as I did an experiment with real hard lead. I got several hundred pound of printers lead. I don't know the alloy, but it pours fine for me. I did notice, that when I was pouring this one mold, that I could not get my finished pours out of the cavity. Well like you said, the lead was expanding while cooling , and I wasn't able to get the pours out without using pliers. Then it dawnd on me, that Do-it mentioned also that some really hard lead will expand. I didn't want to believe it until I tried it and was I surprised. You are definitely correct and confirmed that really hard lead does expand when it cools. Again, your knowledge on all of this is very informative and should help many if they just read the threads and posts.....Thanks Edited June 30, 2009 by cadman Quote Link to comment Share on other sites More sharing options...
JSC Posted June 30, 2009 Report Share Posted June 30, 2009 Sagacious .... Thanx again for some useful information ... all these years and had not gone to the extent of some experiments I should have made. Keep us straight Thanx JSC Quote Link to comment Share on other sites More sharing options...
