Aluminium casting Newbie

To be honest, if your really wanting to do the casting and molding yurself, look for some bentonite, and leave out all those extra items like vegetable oils, starch, linseed oils etc. All they do is contribute to a greensand that is hard to maintain and manipulate. A good 8 to 10% bentonite clay to sand is as good a cheap and usefull mix as you can get. Odds are you can find bentonite in the UK, as its used world wide for all kinds of things. If the drill well over there, and I am sure they do, it could be found though the folks that drill wells.......Usually for green sand its a mix of either western or southern bentonite, and one works better than the other, but regular southern type (calcium based) will work just fine and if all yu can find is sodium based (western) it will work ok for what your doing.

Ok Roy

Never heard the name Bentonite over here its a new one on me I wander if this is the same as what we call Fullers Earth over here a fine white clay that occurs naturally in some parts of this country. ?

Well From what i can gather so far from the net bentonite is fullers earth and is the chief constituent in cat litter and speedi dry (industrial absorbent). I assume fine sand ie silver sand or childs playsand as we call it in this country can be mixed with crushed cat litter and a little water to make a form of casting sand. I wander how many Females realize that fullers earth (used as a cleansing cream by women worldwide) is really crushed Kats litter ! The mind boggles

Bentonite is a fine collodial clay. It is available in a large variety of mesh sizes..ONce mixed with water it expands to many times its original size and has a very pasty stickey texture. A common mix ratio is 100 pounds of sand, 10 pounds bentonite, 3% water. A lot of folks have sucessfully used kitty liter to make greensand, as a lot of kitty liter is made with bentonite clay as its prime ingredient. Its usually the clumping type. Biggest problem though is milling the kitty liter down to a fine enough mesh size.

The big problem with adding the organic type ingredieints you previously listed is they sour or spoil pretty quickly, and are very hard to maintain. I do not know off hand what ufllers earth is, but I have heard that name before.

Regards '

Cool I learned something today, fullers earth is bentonite clay.... You owuld be surprised what it is used in. Its used in feeds, cosmetics, soaps, paints, and many many other items. Look for a mesh size of 200 to 240 for "fullers earth" and a mesh size of 80 to 100 for the sand itself. regular playsand or Silica sand will work for what your doing, although its not the best choice, but its still doable. MIx the dry ingredieints thouroughly.......(the easy part) then add the water a little at a time.....so that it gets to a consistency of..putty. YOu know you have it about right when you can take a handfull and squeeze it in the hand and form a fistfull that is all bonded toghter. THen take that formed wad of greensand and place it in your hand palm side up, and let it span across your ing and index finger. Apply pressure to the piece with your thumb, and it should break cleanly in half. YOur hand shoul dbe relatively free of the greensand and yur hand should not have any traces of water on it.

If its too wet it makes steam when its poured and will ruin the casting. Too dry and it will not ram up tight or have sufficient strength. If its too wet, just spread it out on the floor or in a tub and allow to dry a bit, and remix. Greensand thats used can be added to unused sand and remixed/ retempered to proper consistency. ONce it no longer retempers and retains its green strength its time to add more fullers earth or toss it all and start again. The more its used up to a certain point the better it works, so the darker and more brown/ black it becomes the better is works.

Have fun

Another bit of Trivia about Fuller Earth.

It is one of the main fillers in Acetylene bottles, along with Asbestos and aids in holding the Acetone evenly distributed. The Acetone is there to absorb the gas (from calcium carbide). Were it not for this absorption of the gas, it couldn't be compress more than about 30 psi without becoming unstable and exploding.

The above comes from my memory of things I learned as Steamfitter apprentice, 50 years ago. (and maybe slightly confuse but to the best of my recollection.) FWIW.

Steve

I seem to recall another bit of useless(?) info about fullers earth. It is or was , used with some oils as a stock filler in the finishing of gunstocks. It's used because it won't dull the cutters when checkering the stock.

You probably don't want to learn it.

"Diatomaceous earth is composed of the opalescent silica shells of microscopic free swimming plants while bentonite is a swelling montmorillinite clay mineral that results from the weathering of volcanic ash deposits."

Kevin Gallimore

I new diatomaceous earth was in no way suitable for greensand except perhaps for parting dust......but fullers earth is a montmorillonite clay which should be suitable for making greensand form.

Bentonite is used in so many products its unreal..... There is a huge mine about 7 miles from me that they have been working for years and years. I can get all I want for free if I just go shovel it up in the wharehouse / processing section, as its so plentifiul that they just push it out the door with skid loaders when the clean up the place...Dirt cheap to buy.......but I use sodium based bentonite more than calcium based, and that comes from the western portin of the USA.......I had a seep in my poind last year and pumped it with sodium bentonite slurry and it stopped it up pretty darn quick. I just lucked out and found a well driller that had a tank truck full of the slurry already mixed and needed a place to dump it........My pond was a perfect candidate...

A good general-purpose sand that I use is made from:

Fine Sand 28 pounds Fire Clay 3 pounds Western Bentonite 1 1/2 pounds Water as needed, so that a handfull holds its shape when squeezed but does not feel wet.

This sand mix will have about 15% clay and will give a smooth surface with aluminum if your sand is fine enough. I use a fine grade of sandblast sand from a local builder's supply house. Southern bentonite may have some advantages but the western type is all that is available in my area. You will need to experiment with whatever type of clay you can get locally if you can't get bentonite.

Bentonite by itself will give good results if you have a power sand mixer, such as a muller, available to crush the clay-sand balls that have a tendency to form, however if you are going to mix the sand by hand then the addition of fire clay will reduce the excessive stickiness. At least this has been my experience.

Mike

Yea, I answered the wrong post again. I want to try a clay that is found in layers on sand riverbanks around here, a gray, sticky, fine mess that will stain anything it touches. I want to mix it with beach sand to see if the mixture could have been used as foundry sand long ago.

Here's another use for clay. The gray clay is used to prepare Jersey baked duck (I havent tried it, perhaps Ed has).

Build a fire in the sand. Gut the freshly shot duck. Coat the duck with a layer of the sticky gray clay. Put the clay coated duck in the coals. Go away for a while. Return, pull the duck out of the coals. Crack the clay layer and pull off the clay. Most of the feathers will stick to the clay, leaving you with a plucked ,cooked duck. The clay has absorbed the excess oil from the duck.

Kevin Gallimore

Absolutely wrong. Not even close.

I have Located a source of supply for bentonite in the Uk its available from Potters supply houses in a powder form and is reasonably cheap mail order they also sell fire clay will be trying this out in the near future thanks every one for the input on this I now have a good idea of what I am trying to mix together and cant wait to try it all out maybe this weekend. Also Located some oil bonded casting sand which is rather expensive but similar to petrobond brand in the states. its called Mansbond. The price is =A315-00 / 25 kg bag + VAT. Carriage is =A316-25 + VAT to my area

Think i will try the bentonite sand mix as you all suggest first Thanks for all the tips and interesting remarks on fullers earth Best Regards=20 Ron Priest snipped-for-privacy@hotmail.com