Sooting up skimmers makes slag separate more easily

Discussion in 'Foundry tools and flasks' started by Melterskelter, Jul 3, 2019.

  1. Melterskelter

    Melterskelter Silver Banner Member

    I have noticed in a couple instances brief reference to applying soot to skimmers to make removal of skimmed slag/ iron from the skimmer easier. In one case the video maker mentioned use of a old-school smudge pot. When I was a kid these were very commonly used for nighttime marking construction zones etc.



    To have one of those around dedicated to simply smudging a skimmer seems a bit impractical to me. That is especially true since a fossil-fuel-burning furnace properly run for melting iron should be burning with a mildly reducing flame and so should be a good source of soot.

    Today I experimented with sooting my skimmers in the exhaust stream of my diesel-burning furnace. Sure enough, I could get a nice coat of soot with maybe a 5 to 7 second exposure. And I notice the slag and iron did not stick to the sooty skimmer so I could just knock off the slag by banging it on a heavy piece of steel I have on the ground near my furnace. It is there to serve a an “anvil” for the purpose of knocking slag off skimmers using a 2 pound hammer. If I skimmed a few times on one sooting, I notice some weak adhesion of iron to skimmer. That adhered iron and slag popped loose pretty easily and very cleanly with a hammer blow or two.

    Overall, I felt cleaning my skimmers was much easier if they had been sooted.

    If I am just the last guy to learn this and everyone else has been sooting their skimmers, my apologies.

    Last edited: Jul 3, 2019
  2. Jason

    Jason Silver Banner Member

    You're showing your age Denis....:D I bet you could spray your skimmer with fifty dollar a can Boron Nitride too... ;) Soot is cheaper.
  3. Tobho Mott

    Tobho Mott Silver Banner Member

    You're not the last to learn this; all my dross skimmers currently have thick buildups of various frozen metals stuck to them. I'll have to try the soot trick too...

  4. Mister ED

    Mister ED Silver Banner Member

    I never thought about soot being helpful with such high temps (of course I am a toddler compared to you guys).

    That being said, soot is all I use on mandrels/shafts when pouring babbitt (of course, much lower temps). Gives me a great finish and never any sticking.
  5. Melterskelter

    Melterskelter Silver Banner Member

    I have been sooting up my skimmers and tongs since first starting the thread and have found it to be very useful with no evident downside. For one thing, without the tools sorted, iron tended freeze onto them. Usually the amount of iron was less than a pound, but it could be darned hard to break off with a hammer and breaking it off sent hot bits of metal flying. In the past, twice a bit of hot iron melted a hole in my compressed air line—-grrr. And wasting half a pound of metal or more when slagging was a real waste of material.

    But with a light coat of soot, liquid iron slides right off the tools but it is still easy to snag the slag. For efficient melting, I just keep my furnace running with a barely visible trace of smoke anyway and apply soot to the tools by placing them in the furnace exhaust for maybe 10 to 15 seconds. Just passing on a little trick it took me quite a while to learn.

    Gippeto likes this.
  6. PatJ

    PatJ Silver Banner Member

    LOL, I was just telling someone yesterday that the crazy kid next door taught us how to roll the round smudge pots like bowling balls down the street, which would leave flaming pools of burning oil ever few feet.
    It made for a great flame display. Glumpy (our former resident pyromaniac on another forum) would have loved it.

    I guess I will have to buy a smudge pot; probably not a round one though, just in case there are kids (or Glumpy-types) around.

    I was not aware of the soot thing, and I have had problems with having to break the slag off the skimmer with a hammer.
    The slag will actually shatter, since it is not really iron (assuming you did not scoop up some iron with the slag).

    I am off to ebay.

  7. PatJ

    PatJ Silver Banner Member

    Speaking of smudge pots, they use to use these at the family lumber company, and they worked quite well.
    I looked up the internals of one of these a few years ago, but I forget exactly how they work.

    It is sort of a pulse-jet engine affair, and so I wonder if this technology could be used for a burner?

    Also called orchard camp heaters, made I think by Hy-Lo.

    (these are not my photos)


    Last edited: Aug 7, 2019
  8. Melterskelter

    Melterskelter Silver Banner Member

    I am pretty sure the material I was breaking off of the skimmers was mainly iron as the slag itself has very pour shatter resistance. Skimming out slag WITHOUT dipping the cold skimmer into the molten iron would be very difficult, for me anyway. And that cold (relative to the 2400+ iron) acts just like a super cold steel bar dipped in water---the water freezes to it instantly forming a blob. Since the slag is floating on liquid iron I can never skim without getting into the iron. And it is indeed the iron which can require several smart blows from a 3 pound hammer with the skimmer resting on a heavy hunk of iron or steel to get it to separate from the skimmer. That is, unless the skimmer is coated in soot. Then the iron sticks not at all and generally does not even coat the skimmer. On occasion a thin coat of iron will surround the skimmer but it can be knocked off easily just slamming the skimmer on the hunk of steel or with a light strike of the hammer. Off comes a shiny thin shell and on with the show. The soot needs to be renewed every two or three skims.

    Doing this is just a nicety not a necessity, but it does reduce one recurrently annoying factor.

  9. PatJ

    PatJ Silver Banner Member



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