Green Sand Trouble

[Fuelrush]

Hello, I have a question regarding green sand. I ordered 30lbs of premixed sand off ebay. I wanted to do it myself but I couldn't source a fine enough sand or bentonite clay. Plus it was convenient and saved me time. I got the sand and they also included extra bentonite to "refresh" the sand. I've finished building everything. Furnace, tools, flask, and my first pattern. So I started to work with the sand hoping to soon cast something. I slowly added water and mixed. I finally got the sand to the point it would hold the shape of my palm somewhat, only leaving a thin coat of sand on my palm. When touched it would break fairly cleanly. The problem is its not really rigid at all in any form. When smashed in my hand it will hold its shape but I can just touch it and it collapses. To me it acts like plain old beach sand. I'm lost.

I watched a video of a guy prepare his commercial green sand on youtube. When he smashed it together it appeared that it snapped apart between his fingers like when compressed it was more of a solid. Mine just falls apart.

Is my problem a water issue?
Is it possible my green sand is just sand?

If it would help I could upload a video of how the sand acts.

Thanks for any help!

 

[Artie]

Gday mate, im afraid im not going to be of much help as this is definately a 'feel' proces and hard to descibe properly in words particularly printed words.... but, I 'judge' the state of the sand by the way you have just stated, I squeeze a fistfull which forms a sausage of sorts and then I hold this with 2 fingers of each hand and 'break' it. It holds its shape, but breaks with a clean line and almost no particles fall off the fresh edges.

This is almost purely a result of the clay content. I then add more clay or more sand depending upon what I see/feel, mixing like hell after each 'add'. The clay can take time to make itself 'felt' and a lot of mixing is required and a bit of sitting time (capillary action, taking up moisture).

In my case it was much trial and error over years. The ration of clay to sand should be in the order of 10% or more. You should be able to see it as a dust in the sand particles... it is visable.

Good luck

Rob

 

[tmuir]

If you want to get more bentonite clay I'm told it is sold at places that sell livestock food as its added as a supliment to horses food sometimes.
It is also used to form the slurry for directional drilling.
These are those little machines you sometimes see drilling a hole under a road for installing conduits for comms / electrical etc under roads without digging them up.

Speak nicely to the team next operating one and you may get yourself a part used bag.

I got myself about 10Kg of the stuff from contractors I use to do civil work for us.

 

[tel]

I've never been able to find it at feed places - doesn't seem to be the practice around these parts at least. Best bet is a place that supplies potters - they usually stock it and a host of other goodies as well, including fireclay and castable refractory.

Now as far as sand goes - don't get too hung up on really fine sand. What you are looking for is sand with sharp particles rather than worn smooth ones. I usually just use yellow brickies sand, which is pretty sharp AND has a certain amount of clay already in it. Using this stuff I can mostly get away with around 5% Bentonite. You need to keep the water down to an absolute minimum - just enough to mske it bind and no more. As artie sez, it is very much a 'feel' thing and the only way to get there is by doing it a few times until it starts giving you results. It only improves after you reach that point.

 

[Fuelrush]

I did get to the bottom of the green sand problem. I put some wet sand on a metal plate and let it dry. Then I wiped away the sand hoping I'd see the clay still stuck to the metal. It had a very faint haze on it. I figured that it did contain clay but very little. I separated about 5 lbs of sand and started adding the "Refresh" clay they have me. It took a few ounces to get the clay to what I thought was close to what I needed. The clay actually started clumping and became workable. So I'm way closer to what I needed. Now I can slowly work the rest of the sand more precisely and see what happens. Thanks everyone! I'm sure I'll have more questions!

 

[xlchainsaw]

to make green sand requires a long time.....the idea is to have a coat of clay over every grain of sand!!!i make a slurry and add sand to it....when its as stiff as putty....i dry it!!! then i just add water to sand clay mix as i need!! the more the sand is used ....the better it is!

 

[BenPeake]

Hi everyone,

I'm enjoying this thread as I'm about two thirds through making my furnace and my copes and drags are ready and I'm about to source the ingredients for my green sand. I'm curious about these ingredients as I've read that some people put pulverized coal in addition to bentonite clay in their sand. What are your opinions on this?

Also my furnace is made according to myfordboys instructions (I posted these under the title "Step by step guide to casting") and it's powered by a propane burner. Has anyone tried melting cast iron with this style of furnace with any success?

Cheers,
Ben

 

[xlchainsaw]

Hi everyone,

I'm enjoying this thread as I'm about two thirds through making my furnace and my copes and drags are ready and I'm about to source the ingredients for my green sand. I'm curious about these ingredients as I've read that some people put pulverized coal in addition to bentonite clay in their sand. What are your opinions on this?

Also my furnace is made according to myfordboys instructions (I posted these under the title "Step by step guide to casting") and it's powered by a propane burner. Has anyone tried melting cast iron with this style of furnace with any success?

Cheers,
Ben

cast iron isnt feasible with a propane burner. you will need a oil burner.... im not sure if coal dust will help with brass??? i sure wouldnt like it in my sand. you should be able to get your clay from a farmers feed store..... it comes in 25kg bags... if you ask for bentonite clay they will probally say "dont have any" but if you ask for the stuff you put in dams and feed horses "yes" i was lucky ...i was served by the old owner who knew what is what......none of his staff had a clue!!! i can send some up but it will be cheaper just to buy a bag rather than pay a courier.... a couple of years ago a 25 kg bag cost $12.50 its in pellets. the white common silica sold here is fine ....a bucket costs me $2......however!!!! it needs to be bone dry!!!! and you will need to strain it through a fine tea strainer....takes ages..... when made....lasts for years.

 

[T70MkIII]

I made up my moulding sand using kitty litter! Clumping cat litter is often made from bentonite - just check the ingredients on the pack until you find the right one. Cheap and very available. Percentages of bentonite may vary, but I found one at about 95% from memory, and it worked very well.

 

[xlchainsaw]

cast iron has been known to have melted with a propane burner like 4.5 kgs of gas to melt 500 grs of cast iron!!!!!!
im yet to investigate but the guy that runs the foundry near here claims he uses a burner that runs on liquid gas!!!!
melts copper .... and makes his own brass in 6 kg lots!!! ???? his description is like the old kero/parrifin lamp burners....
for liquid gas he inverts his bottle....umm im trying to get to know this guy....maybe one day he will show me this burner

 

[shred]

Crushed coal in the sand is used extensively in commercial cast iron foundries, but I don't know if it has a place elsewhere in home foundry work. Everything gets coated black.

Here's a shot of a cast iron foundry in Colombia, notice the floor; the entire place is like that.

You can tell somebody's a serious caster when they use a ladder to work on a crucible...

 

[BenPeake]

Thanks for your help everyone.

I went out on a sourcing rampage today and picked up heaps of stuff. I bought sand, bentonite clay, some pearlite for finishing my furnace and an extension pipe for my burner.

I mixed the greensand up and it acts as Artie described. I took Tels advice on the bentonite clay and went to a potter's supplier. I'm glad I did as having it in powdered form sure as hell beats pounding kitty litter to powder. I gave the coal a swerve.

Not too much to do before I can begin learning how to cast, and hopefully not too long after that I'll be ale to put some photos of some finished parts up. Thanks for all the advice - it really helps out.

Ben

 

[Artie]

Mate great to see you taking the journey, hopefully it will be a safe journey (and you can help there). Common sense and a respect for the forces you are working with. The amount of energy stored in a pound of molten aluminium is enormous.

The results are truly rewarding and not to mention convenient. I no longer buy (actually never did... :) lumps of aluminium or brass, simply cast to the approx size I need and go from there. The pic in my avatar is a 'lump' that I cast up...

Enjoy, report back your successes or failures, they are all important to us.

Cheers

Rob

 

[xlchainsaw]

next will be "crucible trouble" after sand trouble that is.

 

[BenPeake]

Hello everyone,

Well I got everything together over the weekend and poured my first casting. I'm really happy with the result for a first go and I'm very impressed with the way my furnace runs (Thanks Myfordboy). So here are the results after having the extra bits trimmed and a few surfaces machined. (I'm sorry I couldn't wait to do this so there are no photos of the casting prior to machining. The Feeder and Riser were arranged on opposite sides of the flywheel and penetrated the sand just below the seam. Despite being happy with the result, I know better results can be obtained so suggestions are encouraged. The casting is of alluminium (scrap) and I added salt to drive off gases and sodium carbonate to make the melt more fluid. The sand is just a mixture of normal sand and bentonite clay.

Thanks for looking,
Ben

 

[Artie]

Looks to me like you are well on your way! You should be very proud of yourself (and are probably wondering why you didnt do this years ago...).

All you need now is practise practise and a little more practise. Every time you cast something you learn a little (or a lot) more.

Just think of this.... you have every size aluminium stock available to you right now. Just needs and hour or so....

Cingrats mate, keep th epics flowin..... :bow:

 

[tel]

Yep, congrats Ben, looks like you got nice solid metal into that.

 

[krv3000]

HI brill I wood not no where to start to do home casting so I ant gowning to attempt it regards bob

 

[Lakc]

Welcome to the dark side

I'm not a green sand expert, I went the petrobond route. From the looks of the casting, I think your sand may be a bit too wet. Venting is critical with green sand, and it looks like the surface of the casting is full of steam bubbles.

All you need now is practise practise and a little more practise. Every time you cast something you learn a little (or a lot) more.

This is very true. One of the things you will pick up on is what you "dope" up your scrap metal with. I rarely use degassing and fluid agents when my scrap is mostly cast aluminum, but sometimes its helpful if your scrap is 100,200, and 600 series.

 

[xlchainsaw]

i dont bother with any degas agents...... i get my best and finest castings from aluminium that ive pigged several times.....if its a delicate cast i will sacrifice a secondry previous casting rather than use fresh scrap...i use "fresh scrap" for rough castings...like casting flasks. ben.... i would say your sand is still a bit new.....maybe ram a little harder....quit using degas....skim and pig your metal....maybe dry your sand completely and run it though a finer strainer????. for a first pour....its terrific! never!!! peer over and look directly into the pouring well....!!!!! try and stay at arms lengths. i dont think your sand was too wet!!! if it was and if you did as i just described!!!!....whooooosh!!! the metal will erupt quicker than throwing water on hot fat!!!