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Thread: Fluxing with Sawdust

  1. #1
    Boolit Master prickett's Avatar
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    Fluxing with Sawdust

    2 casting sessions ago I started fluxing with sawdust. My lead looked better than I've ever seen it. Then, I cast the following time and the resulting boolits looked dirty.

    My technique is to flux with sawdust (about the size of a golf ball) stirring it into the lead fairly aggressively. I scrape the side of the pot and the pour mechanism. I then skim off the sawdust, leaving a mirror finish looking pot of lead. I then sprinkle more sawdust across the top to reduce oxidation. I then start pouring.

    Does this sound like the correct technique? Could the "dirt" be ash from the lead (that didn't float to the top)?

    Also, I tried covering the pot with foil to reduce oxidation. After pouring a while, I removed the foil and looked in. There was a caramel color on top of the lead. Is covering with foil recommended? And, what was the coloring I saw?

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    How much sawdust are you adding before you start pouring? Enough to make a blanket on top of the melt?

    Did you start with a clean empty pot this session? If not, the dirt could be impurities from the alloy that was in the pot.

    How clean are your ingots? Could there be impurities in the ingots?

    The caramel coloring could be from the sawdust ash.

    Your technique sounds good.

    Was there any flecks of lead stuck to the pot walls and the metering rod when you removed the foil? If there was, you need to add more sawdust.

    With a good covering of sawdust on top of the melt, the foil really isn't necessary.
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  3. #3
    Boolit Master
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    I usually let the saw dust turn to ash before I stir it in. (A match helps.) If that is the perfect way to do it, I don't really know? But it seems to work well.
    Qajaq59

    One slow hit is better then 500 quick misses. "It ain't the noise that kills 'em!!!!"

  4. #4
    Boolit Master XWrench3's Avatar
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    i flux with sawdust, and parafin. i flux with parafin first, stirring the heck out of it. then with the sawdust. but i do not remove it. i THINK that i get the best results that way.

  5. #5
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    Just as a side note: If you use cedar saw dust the wife wont mind do bad.
    Last edited by qajaq59; 06-16-2010 at 08:16 AM.
    Qajaq59

    One slow hit is better then 500 quick misses. "It ain't the noise that kills 'em!!!!"

  6. #6
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    I usually let the saw dust turn to ash before I stir it in. (A match helps.) If that is the perfect way to do it, I don't really know? But it seems to work well.
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    Qajaq59
    There was a thread on this recently, where the OP said that he lets the sawdust burn up on the surface and then stirs in into the lead, with excellent results. Apparently, mixing the unburned wood into the lead has no benefit, and you are actually exposing the lead to more oxygen unnecessarily.

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    What kind of pot and where is it stored? When I went from a cast pot or steel pot to stainless my dross dropped by half or more. If it's stored where dust and dirt can get in it then you'lll have dirt in the pot as soon as it melts.

  8. #8
    Boolit Bub Hondo Lane's Avatar
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    Any particular type of sawdust? Hardwood,Softwood?

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    "lets the sawdust burn up on the surface and then stirs in into the lead, with excellent results."
    Letting it burn to ash before mixing will prevent a visit from the tinsel fairy, because no matter how dry you think sawdust is "IT ISN'T". it is the ash you want anyway, mixing it before it turns to ash dosen't really help.
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  10. #10
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    Sawdust, or most anything that turns into carbon will work. Some guys even use leaves. I like the cedar because it smells better, but anything will do.
    And Dragonrider is absolutely right. It is NOT as dry as you may think it is, so be careful.
    Qajaq59

    One slow hit is better then 500 quick misses. "It ain't the noise that kills 'em!!!!"

  11. #11
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    I have also switched to saw dust for the last 6 weeks or so. I am using pine shavings that my friend gave me, they are gotten by the big bag at the feed store.
    They are used for animal cages and he uses them for his chickens.
    Mine are clean right out of the bag. I place about a 1/4 to 1/2 inch on top of my melt
    and let it turn brown ( nice and dry ) then I stir it into the mix. After that I let it sit on top of the mix. If it looks dirty I skim it off and add fresh and let it sit on top of the melt.
    It does a great job in that if you move it to the side with a spoon the metal is like a mirror
    under the saw dust. That tells me it is not oxidizing very much. (good thing )
    Sometimes I add a little wax , the saw dust seems to soak it up and then I stir both into the wax.
    The whole proses seems to work out OK.

    But I have noticed that I get black dirt in my bullets for quite a while after I use saw dust.
    I stir a lot--I stir a little, I skim off the dirt, I leave it alone. It seems to make dirt of some kind that does not float to the top. I also stir with a wood stick.
    What works best so far for me is to use wax, stir while smoking or burning and then remove the dross. I do not over stir, and then a layer of saw dust to prevent oxidation.
    I don't stir the saw dust in anymore.

    I think there are other folks who are having this problem also.
    I would like to know why ? I think the saw dust is a good flux and I would like to know why we are having this problem or what we are doing wrong.
    It seem this would be a good thing to get to the bottom of.
    What say you all.

    EDIT to say--yes my pot has been cleaned many times and my metal is clean.
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  12. #12
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    I was ladle casting yesterday and noticed some thing I was unintentionally doing. I fluxed ( I use Borax) but the slotted spoon I was stirring with had dross and dirt stuck to it and would re contaminate my melt. Doh!

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    Due to the weight and surface tension of the melt, wood ash from the sawdust, or more particularly, the stick used to stir, will get trapped under the lead on the bottom of the pot, just like drops of water in the bottom of a cup full of diesel or gasoline. These pockets of ash gravitate toward the spout on a bottom-pour and will form little inclusions in your boolits.

    Proponents of sawdust fluxing sometimes fail to tell the whole story: I, for example, use a bottom-pour almost exclusively, but NEVER scrape the bottom of the pot with a stick, only the sides, that way the ash can work it's way to the top. I forget to mention that detail sometimes. Bret4207 also mentions using sawdust and agressive pot-stirring with a stick a lot, but I remember he almost exlusively ladle-casts and it doesn't matter if stuff gets trapped on the bottom. If you didn't know that, you might get cratered boolits.

    Sawdust works very well, especially in that you can put extra on top after fluxing/cleaning/skimming and just let it sit there and prevent oxidation while you cast (bottom pour, of course!). You have to take everything in context and remember we all do things a little differently.

    Gear
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    Quote Originally Posted by justingrosche View Post
    I was ladle casting yesterday and noticed some thing I was unintentionally doing. I fluxed ( I use Borax) but the slotted spoon I was stirring with had dross and dirt stuck to it and would re contaminate my melt. Doh!
    I personally have found Borax to be highly unsatisfactory for "flux" for a multitude of reasons, and it is perfectly worthless for ladle-casting. You might give sawdust a try, or chips off of old candles. MUCH easier to skim, leaves a bright shiny surface, and no molten borate glass hanging on your spoon like melted cheese to harden and stick.

    Gear
    You can't fix Stupid, but you can occasionally head it off before it hurts something. --Stephen Adams

    To universalize one's experience and state it as the norm is always thin ice on which to stand.--CharGar

    Being able to separate the wheat from the chaff has always been a valuable skill in all of life's activities. --Bwana


  15. #15
    Boolit Master

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    I have found, PAM works well as a surface flux.
    Forms a great liquid layer all across the top.
    Another solution.

  16. #16
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    So that helps explain why I have better results using wax as my basic flux,
    and saw dust as a top layer to prevent oxidation.
    for a bottom spout pot--stir the wax--don't stir the saw dust
    I like it when we get in dept with the explanations, gives me better understanding.

    Thank you

    Sam
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  17. #17
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    I may have to try sawdust again. I stirred the sawdust in right away and was not pleased with how it worked. Maybe if I do it right, I will have better results.
    ARMY Viet-Nam 70-71

  18. #18
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    When I am smelting I stir the pea sized dollops of wax well into the mix after the surface has been skimmed with a slotted SS spoon.

    Once the flux has had a chance to go to work I get the flat paint stirring sticks and clean down the walls and the base of the smelt pot to get all the debris moving up. If some stays in the bottom, I do not care. I scoop the alloy into a alloy ladle (#4 Rowell) from the shiney stuff at the surface. I do not bother to use CFF or sawdust/shavings in the smelting operation.

    Once an ingot has completely melted and the temps are at least 700 degrees I again flux, but not wax.....now is when we use the CFF etc. A thin layer all over the surface is good. I let it burn down to ash and then stir it into the alloy. Now is time to scrape the sides but not the bottom of pot. This is a bottom pour operation.

    Once the alloy has hit 750 degrees or more and the mold has been heated also we are ready to cast some boolits. Keeping a layer of CFF on top of the surface of your alloy is an excellent way to prevent oxidation and keep the temps of the alloy more regulated.
    Pax Nobiscum Dan (Crash) Corrigan

  19. #19
    Boolit Master
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    Gearnasher, I've used the sawdust for a long time and I haven't had that problem. But the stick I've used for years is a hard piece of mahogany and I can't say that I scrap the bottom much with it because by now it is pointed from being burned over time. I mostly stir and scrape the sides as you mentioned, so maybe that explains it.
    Qajaq59

    One slow hit is better then 500 quick misses. "It ain't the noise that kills 'em!!!!"

  20. #20
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    I have gotten dirt in my melt every time I have stirred the saw dust into my melt.
    Yes I have been aggressive with the stirring. I can't explain how burnt wood can sink to the bottom of molten lead, but it seems to do just that.
    There also seems to be a big difference in weather you are bottom feeding or using a ladle.
    I had the same problem with kitty litter causing dirt. The K/L and the S/D both seem to protect the top of the melt but can deposit what amount to dirt in our castings if stirred into the mix.
    Today I got out the old H&G #68 4 hole Just to prove to myself that I wasn't getting to old here and forgetting how to cast.
    I remelted all the screw up bullets from my now pain in the a$$ brass mold. I used new smelted alloy with 2% tin and the old alloy without the tin.
    Well you would have thought it was raining bullets. I had to refill the old 10# pot
    every 10 to 12 Min. casting on # 4--Yup #4 on the old lee pot.
    I got a pile WC's to last most the summer. I guess I blew through 25 pounds of metal.
    I say without any jesting they were some nice bullets--no dirt and no pock marks on one side of the bullet. like the brass mold.
    I fluxed like I said above. Wax, stir while smoking, skim the top, and then
    a cover of saw dust and leave it alone. I did not stir the saw dust into the mix, and I wont in the future --ever. Doing so has ruined 4 or 5 casting sessions so far and it wont anymore.
    Do as you may --but for me enough is enough.
    As a side note I think when we explain things in the future we should try not to leave out little details, There are to many new folks coming on and we could make life a little nerve racking for them, and for some of us old casters.
    WOW did I say old--am I old now? I got to stop using that word.
    I think for me the most learning happens when we stay on a subject and grind out the problems.

    Sam
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    ***Cohesiveness*Leadership*a common cause***

    The effective range of an excuse is ZERO Meters

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