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  • Spring meet up in Ontario, Newmarket, April 6/2024. Discussion

Casting sand

ShawnR

Ultra Member
Premium Member
So far, the only thing I have done with molten aluminum is to pour it into soup cans or a pipe for stock for the lathe. I now have a project I am contemplating that would involve a mold and am wondering about the sand to use. I have seen some mixes involving sand and clay. I don't have access to fireclay where I live unless I order it in but I did save the clay (dust, kerf poop..) from cutting firebricks this summer. I have about a half of a 5 gallon pail. Is that usable to mix with sand (play sand from home depot ok?) If so, what ratio?

What do you use in your mold (or I guess the term is "flask"?)

Thanks
Shawn
 

Tom O

Ultra Member
That’s basically it. I tried playsand first also but wasn’t happy with the finish of the casting and went to the landscape supply near here and bought some mortar sand 10 bucks for 200 LBS, the bentonite I purchased from a local Ceramic shop for 50 bucks.
Notice the grooves in the cope & drag they will help the sand from falling out of the mold.
 

Mcgyver

Ultra Member
For bentonite, check the label, but I believe cat litter is 100% bentonite. No cat, but I buy for oil spills
 

DaveK

Member
That’s basically it. I tried playsand first also but wasn’t happy with the finish of the casting and went to the landscape supply near here and bought some mortar sand 10 bucks for 200 LBS, the bentonite I purchased from a local Ceramic shop for 50 bucks.
I use Sil 1 sand blasting media from a construction supply place, quite fine and works well for me. Fortunately there is a good pottery supply place in town that supplies bentonite (and fire clay and refractory wool etc. etc.)

Dave
 

justindavidow

(Justin)
Super curious what you're planning to cast! :D

Unless you're interested in reusing the sand for many; MANY castings; I'd recommend ordering some Petrobond and getting your project done. (Though given the shipping costs, unless you have a store nearby that you can pick it up, the cost is pretty high per pound!)

I have seen some mixes involving sand and clay. I don't have access to fireclay where I live unless I order it in

Greensand is.. fickle. The exact blend makes a significant difference to the end casting quality, and unless you have a LOT of patience or want to buy/build a sand muller: it's also a lot of work to prep each time you want to use it.

If you do want to go down the road; I'd recommend Casting for the Home Workshop by Henry Tindell and Dave Cooper (Amazon link) it does a good job breaking down what properties and components of each sand type make it useful for various needs.

Regardless; like @Tom O and @DaveK mentioned: find a pottery supply store nearby and pick up some bentonite, then any landscaping supply to find mortar sand (You'll also need an air-tight container to store it in when unused). There's lots of guides online to mixing and making greensand; keep in mind that they ALL gloss over the time required. (for 50-100lbs: expect to be mixing for a few hours!)

I did save the clay (dust, kerf poop..) from cutting firebricks this summer.

MOST Firebrick is primarily composed of aluminum silicates. These tend (in my understanding!) to break down and round under mulling and thus get finer and finer (and unfortunately smoother!) with each reuse. It's also going to be inconsistently sized (at first) and thus will lead to random surface defects.

For a single use, it'll probably work ok. The more it get's reused; the more venting the sand is going to need to off-gas: the finer the sand gets the more clay is going to be needed and thus the less inter-grain-spacing will be available for the cooling metal to off-gas into.

I wouldn't use it (for long term use) but I don't personally know of any reason it wouldn't work (hypothetically) for one-off usage.

What do you use in your mold (or I guess the term is "flask"?)
Generally I use simple big-box-store SPF wood 1x6's or 2x6's with box-jointed corners: depending on the required volume (and thus the total weight).

Wooden flasks are easy to build but ARE consumable; spills and thin-sand areas will eventually lead to the flask catching fire. As the wood shifts over time; it will need to be planed flat at the interface and the alignment will need to be tweaked.

Everything I've cast before is under 6 inches in at least one dimension, so there's more than sufficient space in such a flask.

If I were looking for something a little more "long term" reusable and lower maintenance; various suppliers sell cast-iron flasks. These don't absorb moisture from the sand, stay flat over time, and allow you to cast using much less sand without destroying the flask. (I haven't found a need for such personally!)
 

ShawnR

Ultra Member
Premium Member
Thanks everyone for the input. Good to be able to hear from the those that have done it. I did find some cat litter here from a couple of years ago but it will have to be ground or pulverized as shown in some on line videos. I can look into masonry sand but I bought some for a project last summer and it looked the same as the play sand I have here. Maybe side by side, I would see the difference. I should start with something simpler I think. Thanks for the guidance.

This is a one off project so could accomplish it with welding or threading. It is a base for a benchrest. I thought it would be kind of cool and good experience to cast the base after making a form out of wood and bondo for some nice lines but I kind of want it sooner rather than later so the idea might get shelved for now. I do have the large billets of aluminum from the soup cans so have a good start. It was the joining of legs to the base that I thought would be nice to pour as one cast aluminum piece, then machine out for the post and feet. Here is an image of one I used a couple of weeks ago and it worked well. They can be had in Canada for about $300 shipped but I see it as a great project for a home shop. @RobinHood and I were looking at some in Cabelas when I was out there with @Brent H and Rudy and I had a bit of a discussion about them so I already have good input. Just gotta get going...:rolleyes:
 

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kevin.decelles

Jack of all trades -- Master of none
Premium Member
Shawn - I started with green sand, but switched over to oil bonded sand for easy of use/re-use/consistency. I bit the bullet back in the early 2000s and shipped up 200lbs of Petrobond from budgetcastingsupply.com (back when it was affordable --not sure they ship it anymore). I then connected with a guy from near 'Clive' Alberta who was testing all sorts of sand. I bound 120 lbs from him over 12 years ago and it is as good as petrobond in some respects, and better in some. He found some sand from a pit out by Joffre..... and mixed it with some clay and oil.

I echo everything @justindavidow put out there.... For my flasks I used 3/4 plywood w/re-enforced corners, glued and screwed. You want something solid because when you ram up your mold you are putting a lot of pressures against the outside form. For oil bonded sand, you can ram is pretty much solid as you don't need to accommodate for steam and such (venting) to the extent you do with green sand.

In Calgary, Calgary Ceramics had everything you could want (bettonite, fire clay, sand etc.). Not sure if you have access to something similar.

I keep my sand in tupperware-tubs, 50lbs/tub, and build a muller (search this side for frankenmuller).

Good luck, and remember that water + molten anything doesn't mix. Always pour on a bed of sand (or plywood) -- never cement. And remember your Kiln can probably ignite paper 3-4 hours after you shut it off.
 

Bofobo

M,Mizera(BOFOBO)
My sand is outdoors in a Rubbermaid, it’s made with play sand and food grade bentonite clay, i would prefer to make a new one with finer sand and plain cat litter. what I made will work but is not ideal, I need more clay to hold the sand, once the pour begins it bakes dry and the course sand falls into the cast.
 

ShawnR

Ultra Member
Premium Member
Shawn - I started with green sand, but switched over to oil bonded sand for easy of use/re-use/consistency. I bit the bullet back in the early 2000s and shipped up 200lbs of Petrobond from budgetcastingsupply.com (back when it was affordable --not sure they ship it anymore). I then connected with a guy from near 'Clive' Alberta who was testing all sorts of sand. I bound 120 lbs from him over 12 years ago and it is as good as petrobond in some respects, and better in some. He found some sand from a pit out by Joffre..... and mixed it with some clay and oil.

I echo everything @justindavidow put out there.... For my flasks I used 3/4 plywood w/re-enforced corners, glued and screwed. You want something solid because when you ram up your mold you are putting a lot of pressures against the outside form. For oil bonded sand, you can ram is pretty much solid as you don't need to accommodate for steam and such (venting) to the extent you do with green sand.

In Calgary, Calgary Ceramics had everything you could want (bettonite, fire clay, sand etc.). Not sure if you have access to something similar.

I keep my sand in tupperware-tubs, 50lbs/tub, and build a muller (search this side for frankenmuller).

Good luck, and remember that water + molten anything doesn't mix. Always pour on a bed of sand (or plywood) -- never cement. And remember your Kiln can probably ignite paper 3-4 hours after you shut it off.

Thanks @kevin.decelles I found the thread on the frankenmuller. Nice job! I don't think I I want to get serious enough to go that route but good to see and read the build. I will report back with any progress I make.

Cheers,
Shawn
 

Tom O

Ultra Member
What is the ventilation like with the petrobond I would think it would give off a fair bit of smoke/burnt linseed smell the greensand with bentonite and water could be used inside the garage making it more -22C friendly. It does have a funky smell when stored for the winter but dosn’t the lastlong.
 

kevin.decelles

Jack of all trades -- Master of none
Premium Member
Well...... smoke is a given. I have an exhaust fan on the far wall (previous owner did painting and such). I crack the overhead door about an inch and turn the fan on.

The smoke starts off intense, tapers, but when you break the flasks open it picks up with the added oxygen.

I typically wear a ov/p100 repirator
 

trevj

Ultra Member
I used to hang with a couple old farts that were heavily in to casting, and maybe their site info is still to be got by searching.

The two Names were Robert (Bob) Grauman, and Rupert Wenig. Both now lost to us, sadly.

Robert was pretty involved with the various back alley (essentially) casting shops that operated around Edmonton, and Rupert was from between Camrose and Edmonton Alberta.

Rupert was casting Iron, with a naturally aspirated furnace, and green sand, and Robert left me his, essentially, entire library of books! Plus some other stuff...

I learned the following from them.

First, There are two types of Bentonite. Western, and Southern. One makes things stick, the other is slimy when wet. IIRC, cat litter, is the wrong kind of Bentonite (Western, IIRC, and is also used a lot as drillers mud in the oil industry. I am pretty sure it was Southern Bentonite you wanted for green sand. According to http://www.ece.ualberta.ca/~wyard/foundry/designlog.html I am correct.

You can cast about anything in green sand, you only need to sift it through, to remove any inclusions, and get the moisture level right, and you are in business. Green sand is about your only choice if you want to cast Iron.

Petrobond pretty much NEEDS a Muller, a device that presses and mashes the oil on to the sand. Think, rotating bowl, with big wide wheels, rolling over the sand mix. A fluffer helps (no, not that kind!) basically a powered unit to break all the burnt bits to small enough pieces that the muller can handle. I have seen several, including Rupert's that were a upside down salad bowl with a bunch of bolts set through it facing up, so as to whir around and break up the bits, as they were fed through a hole over the center of the fluffer. Hard to describe. Dump sand in top, it comes out busted up, around the edges of said bowl. Usually a batch of petrobond has a couple casting cycles before it 'needs' to be mulled. YMMV! When you are really on point, is when you see your own fingerprints transferred to the casting, from the pattern! Petrobond, with fine sand, can take up details well beyond what you would expect.
While I have seen writings suggesting using any old oil to make petrobond, I had been told, that there is a special oil made for the purpose. Sorry, cannot name names, as I don't have them to hand.
 

garageguy

Super User
Premium Member
@trevj thanks for the info. I had mixed up some greensand years ago to do some casting and I used drillers mud. I did not know there were 2 kinds.
 

trevj

Ultra Member
Welcome guys. Just passing on what some friends taught me for the sole cost of me being interested!
 

curmudgeon

(Steve)
It is a base for a benchrest. I thought it would be kind of cool and good experience to cast the base after making a form out of wood and bondo for some nice lines but I kind of want it sooner rather than later so the idea might get shelved for now. I do have the large billets of aluminum from the soup cans so have a good start.
I realize that part of the appeal of this project is to use up some of your aluminium, but consider melting up some used wheel weights instead. Separate the lead ones from the zinc ones, and use either; not a mixture. If you do a nice job of the wood mould I'm sure you'll have plenty of new friends that want a casting too.
 
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