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Green Sand recipe

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  • Green Sand recipe

    Does anybody have a recipe for Green Sand ? The one I made up works ok. But is not that great for hotter metals. It uses 1 to 1.5 parts Portland cement to 10 parts fine sand and ATF fluid to hold the mix together. I think the oil burning off makes bubbles in the cast part. Water would work with this mix but water and liquid brass and copper scars me. I have already found out how moister between two metal mold half's and liquid copper work together.

  • #2
    Green sand

    Typical green sand mix is 10% bentonite clay and 3% water by weight. A good test is to squeeze a fistfull of sand. It should stay in one piece, but should not squeeze out between your fingers. Bentonite clay is commonly used by well drillers to seal well casings at the top of the weld as Bentonite swells when wetted.

    After ramming the mold, use a sharp pointed wire, 3/32 or 1/8 inch to improve the venting of the sand to avoid blows in the casting. It is also not necessary to ram green sand really really hard. If you can indent the rammed sand about 1/8 to 1/4 inch with firm fingertip pressure you have it about right.


    • #3
      I have a book about green sand casting and it doesn't mention anything but sand and a little clay as a binder. I think you need to get a book on green sand casting. I got mine from Lindsay Publications.
      It's only ink and paper


      • #4
        I'm not sure I understand normal portland cement in an oil base sand??? Cement needs water to set up/cure and it's typically a one shot deal, after that, it's just dust without any binding quality.

        As above, water based sand is basically clay and silica sand or volcanic sand. Sharp, clean play sand is good, the finer the better. Sand blasting sand is good too. Particulates are not a major deal while molding, because the dust will usually be bound up by the clay and water. Shaking ot after casting can be dusty, sualy precautons should apply.

        The clay can be fire clay, or better yet, bentonite. Bentonite is used by water well drillers as a sealant and oilwell drillers as a viscosfier. Drilling fluid/drilling mud warehouses will have broken bags virtually free for the asking or with a small contribution to the coffee fund. FWIW, oilwell bentonite is a better fit because the grind is a lot finer. Water well drillers tend to use coarser stuff, up to 1/2" lumps. Clumping Kitty litter has been used,but is a waste of time, IMHO. Clumping kitty litter is just clay and inorganics and has to be ground up before it can be blended with the sand. Huge PITA.

        The recipe is usually 3 - 10% clay depending on the clay quality.
        Design to 0.0001", measure to 1/32", cut with an axe, grind to fit


        • #5
          In addition to the water-based formulae folks have posted above, I found this oil-based one on the net years ago. I have not tried it and have no more information than what is here:

          * 100 lb. of very fine silica sand (100 to 150 GFN)
          * 6 - 7 lb. of Bentone (cheapest you can find)
          * 3 lb. of Indopol L-100 oil
          * 0.10 to 0.20 lb. of Propylene Carbonate (or Methanol or Isopropanol)

          I have no idea what Indopol is nor propylene carbonate.

          A friend of mine just buys Petrobond and carefully scoops out the burned sand with a teaspoon and throws it away after carefully opening the cooled flask, thus avoiding the need for rejuvenation. He figures his time is worth more than the few ounces of sand involved.


          • #6
            I always used Petrobond. It smokes a bit,but no messing around with getting sand the right moistness,etc.. If you only cast once in a while,Petrobond is ready to go.


            • #7
              I got my Lindsay Publickations flier in earlier in the week and was looking at casting booklets. The oil works, theirs no set up time just ram. pull mold and pour. Put sand back in bucket add little more oil mix and go agene. With the Bentonite how long do you have to wait before you pour metal in the mold?
              I will check in to the Petrobond.


              • #8
                You use different grades of sand for different types of casting. From fine sand to coarse sand is used for different effects. It's not a real simple thing.
                It's only ink and paper


                • #9
                  Try thia guy:


                  I got the book and I think it's great. It tells you how to set up and operate a DIY home foundry up to and including cast iron. A foundry is unavoidably stinky and smokey; your downwind neghbors might object.

                  The book is full of recipes for green sand, alternate materials (anyone know what"sill dust" is?) and where to find them. How to build a cupola melter (there's some work involved but it's bone simple). C W Ammen is a real story teller. Most any smokestack industry geek will love it.
                  Last edited by Forrest Addy; 02-12-2010, 03:20 AM.


                  • #10
                    Check out TubalCain's casting vid - shows his muller, he talks about the sand composition, and all the bits needed to whip up a cast part for final machining. There's a couple or three vids in the series.



                    • #11
                      If you want high grade castings I would go with the oil based sand for home use. Green sand is fine if you have a muller and want to mess with getting the moisture correct each time. Silica sand is not very healthy if you are exposed to the dust on a long term basis. A lot of foundry work in the Seattle area is done with Olivine sand, this is not a sand but rather a very fine graded crushed rock.
                      The sand muller does two very important jobs. First it crushes any lumps of burned sand or lumps caused by water (these are dangerous as the steam is something like 1600 times as large in volume as the water it came from) Secondly the mulling action coats the grains of sand with the bentonite which gives the mold strength.


                      • #12
                        You can get a two part binder system, smells and looks like fiberglass resin and hardener, that you use once and then discard. No worrying about having a muller to rework the sand etc.

                        It works very well and gives a very fine finish on the castings if you use a fine grained sand.
                        The shortest distance between two points is a circle of infinite diameter.

                        Bluewater Model Engineering Society at

                        Southwestern Ontario. Canada


                        • #13
                          Greensand recipe

                          Everything that I have read and heard about mixing bentonite and sand says that each grain has to be coated with the bentonite. The only successful way to do that is with a muller. Oilsand, (Petrobond is one brand,) is not cheap; I paid over $100.00 per bag. It is mostly reusable, but for big or multiple castings you need a couple of bags. Have you looked into sand/sodium silicate as a mix? The chemical is quite cheap and it is activated with co2. Basically, you mix the two together; the mix can be stored indefinitely. Once rammed up and vented, co2 is blown through the flask, and the sand becomes a rock. I think that you can even remove the flask. Heat from the pour breaks down the area around the part, so that it comes out of the mold easily. I suspect that the sand could be recovered by throwing it in a bucket of water and the sodium silicate would dissolve away. This system would lend itself to "lost styrofoam" casting.
                          Duffy, Gatineau, Quebec


                          • #14
                            Originally posted by jeremy13
                            With the Bentonite how long do you have to wait before you pour metal in the mold?
                            Green sand casting does not require any "cure time". Most founders do the mold then fire the furnace. When melting aluminum, I've been told it is better to have the mold wait on the metal to be poured than have the melt wait on the mold as stuff can be absorbed into the melt and/or be burned out of the metal as it soaks at temp.

                            The commercial foundry I'm aware of starts their green sand line at the same time the sub arc furnaces are fired in the morning. By the time the melt is ready, the molders have an inventory of molds ready to pour.
                            Design to 0.0001", measure to 1/32", cut with an axe, grind to fit


                            • #15
                              I've never heard of anything remotely like the recipe you describe!

                              Casting is like a lot of things - depends on how involved you wanna get in it.... If youre gonna do a fair amount of casting, then the petrobond type sands are the hands down way to go, if it'll be an occasional thing, then a simple green sand type mix will suffice.

                              Heres the site thats popular with a lot of hobby casters -- they have an oil sand they call 'Jupiter'


                              they have a lot of stuff. Obviously the oil sand isnt cheap - at least they include frt!

                              This site is the place to get info on home casting--

                              If everything seems to be going well, you have obviously overlooked something........