Making "GREEN" Sand

There many be a lot of pictures on some of these pages, so please give it time to load them all.

WARNING!!!: You got a brain... USE IT! Building and working with a foundry furnace is "NOT" child's play. It can be very dangerous and if 'you' screw-up don't come crying back to me! If you don't know what you're doing and didn't take the time to read and study all the safety procedures that are available on the net, and you get hurt that's 'your' problem. You are responsible for yourself and your own actions and safety.

--- "NOT ME!" ---

One thing you should know is that building a furnace is 'NOT' a weekend project..... You can figure on spending at least a month putting one together, (The right way.)

Of course if you're loaded with extra bucks just burning a hole in your pocket there are shortcuts you can do.

Doing my research on the net, I've found 100's of designs. Some were just fire brick stacked into a circle on a steel rack another was nothing more than refractory jammed into nothing more than a cut in half milk jug. :-(

The same thing applies to making green sand for your molds. Everyone has their own "PET" formula for making their sand.... AND many won't give out their 'secret' formula.

My designs are not new... just modified the basic concepts to my own ideas and I think improvements.

I can say without a doubt I've LEARNED ALLOT!!! Of what NOT to do and things I FORGOT to do, and some things I SHOULD HAVE DONE, so if you try to do this understand right off that this is a learning process and you WILL make mistakes.

I'm not sure just what I can show you in the way of pictures, after all it's just a box of sand and clay mixed together.

What green sand boils down to is this:
• The finest sand you can find
• Fireclay and/or well drillers clay (Bentonite) or a blend of both
• water or oil

BUT! with that said; I seen and read of molders using:

Beach sand

Sand box sand

Sandblast sand

THE CLAY:
If you have a Well Driller in your area you can probably buy 100# bags for about 10 bucks, and this will save you a lot of work. The Clay is called: Bentonite

Fireclay is 'not' the same as well driller's (Bentonite) clay. I guess Bentonite Clay is denser, because you use a lot less.

Some molders have taken bags of cat litter and ground it into a powder using a small electric coffee mill grinder (Please check with the boss before you take "HER" grinder for your project ;-) ), or making a ball mill and using marbles to grind it up. (We're talking industrial size marbles 1" to 2-1/2" in diameter.)

"MARBLES?!?!?!?

"YES!" Marbles...
What is a marble? "GLASS"
What is glass made from?!?! "MELTED SAND", so you have no contamination.

OK!? So what's a "Ball Mill"?
A ball mill is nothing more than some kind of a drum/ container, (A 5 gallon pail works good if it has a lid that snaps on tight.), that you can seal; then it's laid on rollers and rotated at about 30 to 50 rpm's for hours at a time. The marbles break up the clay into a fine powder to be mixed with the sand.

A WORD OF CAUTION HERE: This makes a very fine powder, so "USE" a dust mask when every you are working with this clay and that goes for adding it to your sand as well.

Ok, now we have the problem that goes down thru the ages... "Getting the sand to thoroughly bonded with the clay"

You can do this in several ways....

By Hand -- very labor intensive!

By machine -- This could run into some "BUCKS"!

Or a combination of both

BY HAND:
You take your sand and clay and sit there for hours mixing it.. turning it over and over till the clay and sand are uniform and then you slowly add just enough water or oil, so when you grab a handful and squeeze it. It compresses into a thick hotdog like shape. When you open your hand you should see the impression of your fingers in the sand and there's very little loose sand left in your hand, (That's part 1). Then when you 'Snap" it in half. If it breaks clean and doesn't crumble or fall apart; "YOU GOT IT!"

The old "Sand Crabs" as they were called; used to do everything right on the floor. Making long windrows and using a long flat blade shovel, scooping up a shovel full and flipping it over and smacking it down with the back of the shovel after hours of that he would slowly start adding his water or oil and start all over again till it was just right to his hand compression test.

Now doesn't that sounds simple --- "RIGHT?!?!" All You'll need is at least a 150 to 250 pounds made up before you even think about ramming up your first flask.

(Flasks are another topic, but the bigger the part the bigger the flask and the more sand you'll need to fill it. A 12" X 16" X 6" flask will take about 80 pounds DRY weight to 150 pounds WET weight of sand. Figure on getting a medium size garbage can to hold your mixed sand)

BY MACHINE:
The machine to make your green sand is called a MULLER.
They come in all different types and sizes; but what it basically does is compresses the clay onto the grains of sand, (coating each grain of sand with a layer of clay).

A common type is a big heavy walled drum with 2 rotating wheels (Normally 25 to 35 lbs. each wheel), and scrapper blades. The wheels compress the clay and sand together and the scraper blades break it up and stirs it around. After a few hours of dry mixing you then start adding in your water or oil. This can be a very expensive machine to build.

THE POORMANS MULLER:
Let's see if I can explain this clearly. I guess I should make another page just for this one, but that will be a while. As of this writing I'm still building furnaces and CNC Milling machines.

Take a 5 gallon bucket or a small to medium garbage can and mount it on some kind of a turntable, (Slow turning not over 40 rpms), seeing that a garbage can has a recessed bottom you could make it so it sits over the turntable and use screws or bolts to hold it in place. Then make an overhead 'u' shaped bracket that just clears the top of the bucket by a few inches, 6 inch at the most, (Think of an upside down square ended "U" ), In the center of the U bracket drill a 3/4" hole. (This bracket has to be strong enough to take the pressure and twisting of mixing the sand.)

Take a 3/8" or 1/2" flat bar about 2" to 2-1/2" wide and about a 1/2" shorter in length then the inside diameter of the bucket.

Drill a 3/4" hole in the center. Then you have to measure out an inch each way from the center. Keeping the 2" center section flat, heat the bar with a torch and do a "Quarter" (45°) "twist" from there to the end of the bar on both sides. Then check to make sure the bottom edges are inline with each other. (The bottom edges should be flush against a table or straight edge.)

Next take a 1/4" x 1-1/2" x 6" flat bar and form it to the inside diameter of the bucket and weld that on the ends of the twisted bar so that leading end is about a 1/2" past the end of the twisted bar and they will 'just' scrap/rub against the sides and be flush with the bottom of the twisted bar... on the back end of this scrapper bar add a little more bend or hook to it so it will push the sand back into the center. Braze or weld a 3/4" nut over the center hole of the "TOP" of the bar. (making sure the side that's bent down is facing into the direction the bucket turns. so if you're looking straight down into the bucket and it turns clockwise the right side of the bar should be down and the left will be up. Can you see what happens? the left side facing up compresses the sand down against the bottom of the bucket and the right side scraps the sand back up off the bottom of the bucket.)

Next get a 3/4" ready rod, ( the rods that have threads the entire length -- NOTE: The bigger you make this Muller the bigger this rod has to be.) and several nuts and lock washers. On the bottom end of the rod spin on a nut 'then' a lock washer then thread on your twisted bar so it's flush with the end of the rod and tighten down that top nut to lock it in place. On the top end of the rod spin on a nut then lock washer far enough down so you can get the bucket in place, then slip it into the hole in the 'u' shaped bracket and put the bucket in place and lower the (Now) mixing rod down to the bottom of the bucket. Spin the lower nut up and put a lock washer and nut on top of the bracket and tighten them up. (NOTE: You don't want the mixing bar tight against the bottom of the bucket... if anything it should be about 1/32" but not more than 1/16" off the bottom.)

You now have a poormans muller.

The bucket turns on the turntable and the twisted blades --- one side compress the other side scraps it up and the side scrapping bars help roll the sand back into the center and keeps the bar centered in the bucket...

Side Note: If it looks like it isn't working right --- you might have made the blade upside down or turning the bucket the wrong direction. You can fix that by either changing the rotation of the table or make a new bottom bar with the nut and scrapper bars welded on the other side, "OR" you welded the scrapper bars facing in the wrong direction.

How much you can mix at one time will depend on how powerful your turn table is. If you got a 1-1/2 hp motor and you gear reduce it to 30/40 rpms at the table, it "might" be able to do 40 to 50 pounds at a time.

FOLLOW-UP SIDE NOTE:
After you get you muller working you might want to consider reinforcing the bottom of the bucket. This can easily be done by adding an 1/8" plate to the inside. Cut an 1/8" plate to the exact diameter or maybe even a 32nd bigger. Put it in tight against the bottom and turn the bucket/garbage can over and drill small pilot holes all around the inside edge and about an inch in from the edge; (About 3" spacing is good), then another circle of holes closer to the center. Take a black magic marker and mark a spot on the plate and the bucket so you'll know where it lines up with the holes you've drilled. Remove the plate and drill and tap to whatever size you like, (1/4-20 is a good and common size). Drill out the holes in the bucket to fit the size you choose. Now replace the plate and using the biggest flat washers you can get; bolt it in. Making sure that you don't use too long of a bolt. If it's too long you may have to use extra flat washers as spacers or just get shorter bolts.

Another type of muller is like the old style cement mixers:
They have the tub and then a cross shaft with paddles in it. You might be able to find an old one laying around in some junk yard or check at a cement contractor and see if they've got one they don't use any more. You'll have to modify the paddles and maybe replace a bearing or two, but it's a lot cheaper. Forget about the newer styles with the rolling drum, they turn to fast and the sand/clay mix is just to thick once you start adding in the water or oil.

OK! So now you how to mix up your sand, so let's talk about the 'secret' recipes that are out there.

Some recipes go by weight and others go by volume and it can get confusing. I had one that went by both ways. You can keep it very simple at the start and after you learn more about it; start adding in the other enhancers such as:

• Sea Coal
• Silica Flour
• wheat flour
• wood flour
• corn flour
• sanding dust from hardwood
• Linseed Oil

but if you're just pouring Aluminum and Brass it really isn't necessary.

OK, so you went out and bought the finest sand possible. NOW how fine a surface finish do you want on your casting?

Plain Jane ? What ever comes out is fine...

Then you can start mixing right now, BUT! if you want the finest surface you can get then you got a little work to do. You need to find the finest mesh window screen and make a small frame and staple or nail it on then sift all that sand -- Keep the coarser grain sand for the rough casting and use just the sifted fine grain sand for the better surface quality castings, also check your clay as well, it will lump up if it's been sitting in some warehouse and got damp though condensation.

When mixing your sand you want enough clay to bind the sand together, but not so much that it chokes off the natural venting/breathing of the sand and the same holds true for the water or oil. You want it to feel 'damp' but not wet in your hand. Soak a wash rag then ring it out hard... That's what you what your sand to feel like.

Now you have to think in 'mass'; if you take 25 lbs. of clay and 100 lbs. of sand that's not 25% clay because you have a total "mass" of 125 lbs. so that's only 20% and is a good starting point for a blend, although I would work up to that slowly and keep checking your mix by the hand compression test. (Note: A lot depends on the grade of sand and the type of clay you're using. Fireclay is "not" Bentonite clay! They are different and the percentages used will be different. In fact some recipes calls for both.) To much clay and you got 'mud' to little and it won't hold it's shape or do a clean break and to wet a mixture and the clay will wash off the sand and you'll wind up with mumps of clay in your mix; use as little water as possible, a 125 lb. batch will use less than a gallon of water.

Start out by making small batches of 10 lbs. and see what blend works best, then you can make your larger batch. Figure on getting 4 -- 80 lb. bags of sand and 2 -- 100 lb. bags of clay to start with. (This clay and sand will also be used in your refractory mix for lining the furnace.)

If you have to adjust your mix -- remember to do it slowing... never add more than 1% of the 'mass' at a time. Using the above 125 lbs. -- that's 1-1/4 lbs. BUT that might mean only a cup or two -- volume vs weight.

OK, Standard rule of thumb in mixing:

Mix dry -- clay and sand till completely blended.

Use a small garden sprinkling can to add the water or oil.

Add in small amounts then mix completely.

Use as little water or oil as possible.

Wait at least an hour or more before doing the hand compression test.

Store in a container that has a tight lid.

'IF' your sand has been sitting in the storage container for any length of time -- remix it before using.

Don't be in a hurry to test your mix. The clay absorbs the water a lot slower than the sand, so after your have mixed it thoroughly let it sit for an hour or more, then mix it again and do your hand test.

After you've gotten this mix working the way you want it and you're ready to experiment try the same mix, but use synthetic 2 cycle oil. Ams/Oil makes a very good synthetic, you can check out their store here.