Spraying Mold Cavities

Discussion in 'General foundry chat' started by Skratch, Aug 9, 2022.

  1. Skratch

    Skratch Silver

    Does anyone spray the mold cavities to set the sand? If so what do you use? I've been using spray paint applied about 3-4 times, allowed to dry between coats. After pour it peels off in a sheet from the sand and seems to give a smoother finish than just the facing sand.
    Just curious, any opinions or tips appreciated ,,,, :)

    Thanks,, John ...
     
  2. Skratch

    Skratch Silver

    Hmmm, I must be the only one,,,, ;)
     
  3. HT1

    HT1 Gold Banner Member

    what sand are you using??? and what metal are you casting

    V/r HT1
     
    Skratch likes this.
  4. Skratch

    Skratch Silver

    IMG_20220618_225854 (2).jpg I'm using local natural sand/adobe clay, finely sifted and casting red brass. Not a very good pic.
     
    Tops likes this.
  5. HT1

    HT1 Gold Banner Member

    [​IMG]

    where are you local to? so we can take wild A$$ guesses about your sand,

    and what metal are you pouring,? I'm going to take a WAG its a bronze of which there are about 6 Gazillion varieties,

    Now spray paint in no way is a mold coating, so perhaps do a little research on mold coatings or washes , that is what you should be using, in a natural accruing green sand you can get some great surface finish results with very simple mold washes https://maritime.org/doc/foundry/index.php#pg44 has one, a couple of other members here have done research on washes with great results from available items like fireclay

    V/r HT1
     
    Mark's castings likes this.
  6. Skratch

    Skratch Silver

    I'm in SW NM USA. The sand is what we call blow sand, it's very fine sand and adobe clay, no rocks,
    pebbles, trash etc. I have to hand mull, let it set a day in an airtight container.
    It sifts easily, rams tightly. I use the spray paint to lightly coat the mold cavity and set
    grains to help prevent any detachment while handling the completed mold prior to casting. I had one
    do just that, ruined the cast, no problems since spraying. Also after casting the paint will peel
    off the sand in a sheet making it easier to reclaim the sand if need be although I have an unlimited
    supply providing the sand is accessible, snow, overly wet from rain, etc.
    The metal is from commercial potable water meter casings. It has a light bronze color right after casting,
    turning a golden bronze patina after time, polishes to a high sheen. I called it red brass for want of a
    better description but I think it's probably some type of a bronze alloy.
     
    Keith likes this.
  7. HT1

    HT1 Gold Banner Member

    now that is some good info water meters are indeed a red brass that color means it is probably a newer lead free alloy, the older ones are often 85 5 5 5, and will stay a reddish color ,
    you need some clay in that sand , southern bentonite . adobe clay will be western bentonite, you need a mix of both for really good green sand


    as far as mold washe go watch this video and take notes

    Sandrammer has forgotten more then I know on the subject
    V/r HT1
     
    Skratch likes this.
  8. Skratch

    Skratch Silver

    Very interesting video and thanks for the info on the bentonite difference, I'm smarter
    now. ;) I'll get some southern bentonite and add some.

    Thanks again
    John,,,,
     
  9. Skratch

    Skratch Silver

    Just a quick post to show how the spray paint peels off the mold halves, the
    paint from the cavity turns to a black powder and will just brush off the casting.

    IMG_20220819_193132~2.jpg
     

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