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Thread: Sand Core Making Processes?

  1. #1
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    Sand Core Making Processes?

    Okay so I have heard of several different ways of making sand cores. Most involve Sodium Silicate or Baking. So my Question is. In your opinion which one is the best way to go? There are three ways that i have heard of:


    Sodium Silicate:
    mixed with sand and Gased with CO2. Being the easiest and quickest to set. although this is fairly expensive for the beginner Hobby Caster.
    Procedure:
    Taken from Bugetcastingsupply.com
    Mix a fine grained sand (try about a 100 mesh to begin with) with 3% to 4% by weight of the sodium silicate. Mixing can be accomplished in a small container by hand for small jobs. Larger batches can be mixed in a muller.

    Pack the treated sand into a core box that forms the desired shape. Insert any wires, rods or other support items as required.

    To solidify the core, apply CO2 gas from a low pressure source such as a beverage gas cylinder. The gas can be applied using a hose and any convenient nozzle. The nozzle could be just the end of the tube, or a diffuser such as a standard kitchen funnel. The object is to push the gas thru the core from one end to the other, and activate the sodium silicate to bind the sand. It's also practical place the core mold in a plastic bag and flood it with CO2 to kick off the core inside.
    There is also a lot of information on Jammers Homemade SS here.

    Linseed Oil:
    Taken from
    Quote Originally Posted by myfordboy View Post
    I have a recipe for baked cores at http://myfordboy.blogspot.co.uk/p/core-making.html
    I have swiched to Sodium Silicate cores now but I think there is still an occasion when a baked one could be better
    Here is the recipe:

    525g Wickes sharp sand, sieved with kitchen sieve to remove larger stones
    ( Wickes is a builder’s supplier in the UK)
    18g Flour ( plain)
    10g Solvite wallpaper paste, dry weight, mixed with minimum amount of water.
    12.5 ml. Boiled Linseed Oil


    Put sand in a plastic bag and add flour. Shake till mixed. Add paste and work the bag between your hands until mixed then add the linseed oil. Make the mix as dry as you can so it will harden quicker.


    Ram into core mould . Leave in a warm place until you feel its safe to beak the mould , It will still be quite soft and needs cooking slowly, in the kitchen oven, building up to full oven temperature of 250C when it will be a dark colour and begins to smoke. .


    Molasses - Again I have heard of this being used but as of yet have not found a way to do it, so feel free to elaborate.

    Taken from HERE
    Cores or Stone Cookies Recipe:-

    10 litre Silica sand
    1 litre Plain Flour
    500ml Tap Water
    50 ml Molasses
    1 Sieve
    1 Mixing bowl
    1 Trigger Spray bottle
    1 core box
    1 oven (working)


    Sift sand and flour into Mixing bowl
    Dry mix thoroughly

    Place 50 ml Molasses into empty Trigger Spray bottle
    Add 500 ml tap water then add trigger cap to bottle.
    To be shaken – (not stirred) until mixed.

    Spray sand mixture and mull to a good bond is achieved
    Powder corebox
    Ram mixture into corebox
    Remove core from corebox
    Place core in oven at 180 degrees C for half hour
    Allow to cool use the resulting rock as required.
    The pleasant odour of the cooking is replaced by a less pleasant version, left in the sand after casting.


    Just trying to put everything together in one place for a quick reference for myself.
    Myfordboy, if you prefer i not use yours let me know and i will remove it.
    Last edited by Jexstir; 04-04-2012 at 05:00 PM. Reason: Added reciepes I have found from different sources
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  2. #2
    Senior Member HT1's Avatar
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    there are several others, most completely out of the hobbiests budget, Sodium Silicate is very good, reliable and repeatable, little complicated for the hobbiest, got to get a Co2 tank , for oil, linseed oil, not petrobond, http://www.hnsa.org/doc/foundry/index.htm#pg48 is a great place to start. I'm not old enough to have worked with molasses cores. I did not think it was a major binder, but an addative to promote collapsability, but I could be mistaken.

    i know it is a horrable admission, but I just try and avoid all core work, unless it was personnal and something I really needed, I know there are few paying jobs I could get my money out of if it required core work

    V/r HT1
    Last edited by HT1; 04-02-2012 at 07:05 PM.

  3. #3
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    Good greensand means you can do a lot of work with greensand cores, which are quick and easy.

    If I need more durability than greensand I go sodium silicate. I've found baking it to be superior to trying to cure with CO2. The disadvantage is, sodium silicate cores can be very difficult to remove. I've done molasses and had marginal success with it, and I had no success at all with linseed oil.

    The other option is a commercial binder, which ought to be fairly foolproof if you can get it. Not something I've used.
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    I can buy sodium silicate locally for about $12/gal. That said I think I will save my molasses for making cookies. Um,Um,Good
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  5. #5
    Jexstir, have you seen my Core making video?
    The gas in that video came from this CO2 rig I made using a paintball tank and a surplus pressure regulator. Myfordboy also has at least two or three videos on youtube that feature core making.

  6. #6
    Senior Member 4cylndrfury's Avatar
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    Quote Originally Posted by hobiejack View Post
    I can buy sodium silicate locally for about $12/gal.
    What kind of place is it? A foundry supply business? Id love to find a local to me brick and mortar to buy the stuff rather than use the internet...

  7. #7
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    4cylindrfury,

    I would bet any good ceramics arts supplier near you would have it. In Denver, about 65 miles south of me, there is a company called "Mile High Ceramics." They sell sodium silicate for $11 per gallon. They also sell a ton of other interesting ingredients for this hobby.

    Here is a link to their catalog:

    www.milehiceramics.com/Catalog/Mile_Hi_Ceramics_2012_Color_Catalogrfs.pdf
    Last edited by BashingTin; 04-03-2012 at 05:10 AM.

  8. #8
    Well, I tried to find the thread, but as usual my search abilities let me down. Search for the "rock cookie" recepie, that's the molasses based one, and I've gotta say, it works pretty good. You do have to bake it, but at least it doesn't smell bad when you do so the Mrs. won't give you grief about using the oven. It is also quite easy to remove from the casting afterwards. It does smell like burning popcorn when you cast with it, but hey, it's cheap. I would also make sure that you have the core vented well, so that any gas generated can escape. SS works good, too, but I'm in the same boat as far as trying to find it locally. The ceramics shop that I got my previous batch from is gone now.
    Vade Libram Harenae.

  9. #9
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    Two part epoxy resin works good if you don't mind waiting for it to set. Great for making really thin complicated cores. 2% by weight. Bit expensive if you do it alot. Make sure your corebox is drafted correctly or you may break it before the core.

    Paul

  10. #10
    I have a recipe for baked cores at http://myfordboy.blogspot.co.uk/p/core-making.html
    I have swiched to Sodium Silicate cores now but I think there is still an occasion when a baked one could be better.

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