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Thread: slag

  1. #1


    when I melt my wheel weights and skim the slag if I let it cool and remelt I get more slag. what am I skimming off? am I loosing alloy materials?

  2. #2
    Boolit Buddy
    Join Date
    May 2016
    When you have molten alloy in contact with atmosphere a grey metal oxide layer will form on top. If you are skimming it off you losing alloy materials, especially then tin.
    Instead add a source of carbon such as paraffin or bee's wax and it will reduce your oxide back to metal.

  3. #3
    Boolit Master BNE's Avatar
    Join Date
    Mar 2013
    There is a lot of "fake news" when it comes to what alloys you are losing. I've done a LOT of XrF testing where I overheated the pot (~900F) and tried to skim just the top layer of alloy off and analyze that. Based on all the online discussions, I expected the layer to be Tin rich. It was no different than the base alloy.

    Yes, the grey layer on top of a clean melt is probably Tin oxide. BUT it is too thin to make any difference in your alloy mix.

    The initial gunk you are skimming off of wheel weights is who knows what. Unless you a skimming a pot off that is barely molten, you are not removing enough alloy to worry about it.

    I'm a Happy Clinger.

  4. #4

    JonB_in_Glencoe's Avatar
    Join Date
    Mar 2010
    Land of 10,000 Lakes
    Here is some great info for you about Slag/Dross.
    "From Ingot to Target: A Cast Bullet Guide for Handgunners©" by Glen E. Fryxell and Robert L. Applegate.
    Read the whole book when you get time.
    “If someone has a gun and is trying to kill you, it would be reasonable to shoot back with your own gun.”
    ― The Dalai Lama, Seattle Times, May 2001

  5. #5
    Boolit Buddy wyofool's Avatar
    Join Date
    May 2013
    Smith Valley
    Thanks BNE that makes a lot of sense. Keep Happy

  6. #6
    Boolit Buddy Teemu's Avatar
    Join Date
    Aug 2017
    Even after fluxing still some dross may appear on surface. Atleast i had some. Been skimming it off on tin can and at this moment i have 10ltr bucket half that dross. When it is full it is time to take it on to junk yard and get my paycheck from it.

  7. #7
    Boolit Master

    Bookworm's Avatar
    Join Date
    Jan 2016
    Central Oklahoma, on a dirt road.
    Don't be in a hurry to scrap that dross, or slag as you are calling it.

    I rendered several hundred pounds of assorted lead, mostly CWW, but had some SWW and plumbers lead too.

    I saved all the dross, and rendered it separately into ingots. I put the dross ingots aside for a time, then sent a sample to BNE.
    The dross sample came back as Sb 1.9%, Sn .4%, balance Pb.

    IOW, the dross came back as CWW.

    Now, all my dross collects in a coffee can, and gets tossed in with the next batch of CWW when rendered.
    "Varium et mutabile semper femina." - Virgil
    Man, ain't it the truth....

  8. #8
    Boolit Grand Master

    Join Date
    Oct 2009
    Like BNE says, its probably a mix of lead and tin oxides with whatever paint, dirt of grease that was on your scrap. I don't save this stuff when I'm smelting scrap but I do save it from my casting pot. This goes back into the next smelt, for whatever good it does.

  9. #9
    Boolit Buddy Teemu's Avatar
    Join Date
    Aug 2017
    I only smelt lead and it should be pure. I have corner on my basement where are "unknow alloys" need to give samples to my friend who has possibility to check what it holds in. So it is most likely some oxidation from lead. And i do use sawdust on smelting and flux all my smeltings

  10. #10
    Boolit Master
    Join Date
    Sep 2016
    I've process thousands of pounds of antimonial lead, and saved all the dross. I've processed just a small fraction of it, but ended up with twenty odd pounds of a hard alloy.

    I intend to process it all, combine the lots, and get an analysis.

    Honestly, while some of my "dross" is what I skim off of the top of a pot of clean metal, most of it is metal containing sawdust ash. While I try to skim just the ash, and even though I don't often see liquid metal dripping out of left in the perforated skimmer, what gets dumped in the can often cools into a hard, heavy lump rather than fine light powder. So maybe I'm just scooping out alloy.

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check