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Thread: Why is my sodium silicate not binding?

  1. #1

    Why is my sodium silicate not binding?

    I mixed some sodium silicate today and unsuccessfully tried to make a core. For some reason the sand mixture wouldn't bind.

    Any reason why it wouldn't bind? Maybe too much sodium silicate? I had the CO2 pumped for a while. There was no spot where it was hard, the thing just crumbled.

    I've used this mixture before, but not for such a big core (the diameter was about 3.5in and the whole thing was about 8in. The sand has been in the outside shed and it's been freezing temps lately. I made this in my house so it was in room temp.

    I ran out of the sodium silicate so I'll have to wait until I get more.

    Any ideas?

  2. #2
    Senior Member HT1's Avatar
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    You had the CO2 pumped for a while???, too much CO2 at too high a pressure will cause the sand to crumble, but it will get hard ... after gassing did the sand still feel sticky/ wet or did it get dry... only two possibilities I can think of off my head, bad SS or overgassing


    V/r HT1

  3. #3
    Moderator DavidF's Avatar
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    I've been wrestling this myself a bit. My main two thoughts for my problems are that the SS has gotten old, or I am mixing it too long and its drying out before I gas it. I will be replenishing my supply shortly and eliminating the possibility of the SS being old.
    What ratio are you mixing at?
    A calm sea does not make a skilled sailor....

  4. #4
    Senior Member HT1's Avatar
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    here is what the Navy has to say about CO2 sand... good info Sorry it is sideways, save it rotate and enlarge

    V/r HT1
    Attached Images Attached Images

  5. #5
    Ugh, my mistake. I had two tubs of playsand and I forgot one of the sand was premixed with bentonite which I haven't used in ages. They both look so alike when dry!

    I just tested a small sample with whatever I had left of the sodium silicate and the real playsand and all is good again!

  6. #6
    This is the SS that I've been using. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 The cost wasn't bad and it has worked great. As for size? I have made the whole mold out of SS say a 9"x9"x8" flask. I'm not really good with weighing it... I mix about 1/2 a 5 gallon bucket of sand with just enough so that it feels like greensand (anymore and it's a pain to get out after the cast...like hammer and chisel pain ). Gas it and let it set overnight. Been happy with the results.

    CBB

  7. #7
    The stuff I used in this video came from a pottery supply place, it costs about $15 a gallon, the CO2 came from a 20oz paintball canister.



    BTW, this video was shot in a single take, no cuts, no editing, it shows the whole process, start to finish, in real time.

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