Casting sand

[Tobho Mott]

Capilano college used to have a casting program but closed it down in about 2013. They sold off their muller and a local fellow here bought it. When he picked it up the fellow on the loading dock said "That has to go too". He said it was petrobond and there were 20 or 30 20kg sacks of it. I got 2 of them but I am still trying to figure out what it is. The bags are deteriorated but it says "Hy-Bond" on the front and "A Hy-Bond product" from a company called Fairy and Co. in Surrey on the back in smaller print. Of course they have long gone out of business. I talked to a fellow at Greenbarn pottery in Surrey who said he worked for Dave Fairy when he was a student 30 years ago. He knew nothing about casting but said they had a whole line of products that went under the generic brand of Hy-Bond. He said they had several products where they bought the raw material in large quantities and repackaged in smaller bags. It is a pale yellow and if there is sand in it it is extremely fine (to the point where I think it is a straight clay product). I have a bit of bentonite from a pottery shop and it does not act at all like this stuff. Bentonite with water forms a thick slippery paste. This stuff does not mix with water at all and just settles out. I tried Varsol and 10 weight non detergent oil but neither mixed or dissolved the clay. If anybody knows anything about this stuff I would love to hear about it. I tried to track down a fellow that knew quite a bit about the Capilano course but he did not respond to my email.

Brian

I really meant to come.back to this thread sooner! Sorry. I hope late is better than never...

Do you think you might have the organoclay binder that can be used to make oil bonded sand? If so that is something I've been hunting for, for a few years. Nobody wants to sell me less than a pallet of the stuff.

Denis Foster (makes cast iron straight edges, I know him better as melterskelter from the home foundry forums) did some interesting comparisons between western bentonite, southern bentonite, and bentone organoclay mixed with oil, water, and both. Perhaps his results will help you figure out what you have:

Identifying bentone vs bentonite based on physical charecteristics.

Background: In another thread (http://forums.thehomefoundry.org/index.php?threads/mixing-up-k-bond-sand-similar-to-petrobond.1759/) on mixing K-Bond...

forums.thehomefoundry.org

Good luck!

Jeff

 

[bhowden]

When I first got the clay I was very hopeful that it would be suitable for oil bonded sand as the loading dock guy referred to it as petrobond but I am pretty sure it is not. I have run the tests you linked and it does not act at all like either form of bentonite. My best guess at the moment is that it is some sort of refractory clay for repairing a furnace.

Brian

 

[TonyK]

Sand casting. Interesting stuff. My first question is how desperate are you and how much money do you have to spend. Take a look at Princess Auto https://www.princessauto.com/en/petro-bond-casting-sand/product/PA0009028150 Expensive but, so is everything these days. Ten pounds $100 that is a bit nuts. I have purchased it from a place in Milton Ontario years ago ( 11 years ). 50 LBS with tax and delivery $200.

First Petro bond sand can be used for aluminum and brass but cannot be used for steel. Sand for steel uses Bentonite and a bit of water due to the high heat of the metal to be poured. Petro Bond sand uses a clay called Bentone and it is a redish brown colour. It can be reused but you have 2 choices when the metal is poured the oil burns off and the sand becomes black and dry. Once the part has been removed you can discard the black sand or it needs to be reconditioned. Meaning you need to add more clay and oil to that sand to allow you to reuse it. It also must be sifted. I purchased 20 pounds of Bentone from a fellow in New Jersey and the Synthetic oil ( see attached picture )from Walmart in the USA and still have half a gallon.

As for smoke, don't open the mold until it cools, depending on how big the part is, well, it may be the next day. Here is a video I did years ago

If the link will not open then go to my channel, go to YouTube and search for fiatx192040 and search title for Home Metal Casting the Heat. I am casting an aluminum hammer form that weighs about 15 pounds. The video is only 3 minutes. It is only the pour not opening the mold.

Here is a more detailed video of the sand casting process done in my shop.

Flask's can be made of wood providing that you have at least 1" of sand between the part and the side of the wooden flask. If not, then it will burn. Also large parts the aluminum tends to lift the parting lines of the flasks, so they should always be wired together to prevent this from happening. If you forget then the flask separates and the molten aluminum dribbles down the side of the flask and catches fire.

Also it should be noted that to activate petro bond sand after it has sat for a while it needs to be dribbled with white gas or naphtha camp fuel. This causes the oil in the sand to become sticky. When the sand is mixed, mulled or beaten, when you run a gardening shovel backwards through it, it should appear to look like cookie dough. Grasp a handful and compress it in your hand now break it in half. If it breaks cleanly without crumbling you are good to go.

TonyK.

Grimsby Ontario Canada

 

[Tobho Mott]

Nice setup. I have some casting videos up on YouTube also.

FYI Tim Smelko retired since you bought your sand, so the Smelko Foundry Products in Milton you knew is now called Foundry Supply Source, and they've also moved to a new address. Still in Milton though. I have an email from almost exactly 2 years ago with a quote in it - at the time they were selling petrobond for $155 per 25kg bag, before tax or shipping. But I understand it's gone up by at least $30 per bag since then. Last time I was there, hobbyists with cash in hand who'd called ahead to set up a visit didn't pay tax. I'm making a run there next Friday to get ingredients for cast iron rated greensand and some ferrosilicon inoculant. Their petrobond is pricey but it's a good deal, especially compared to the tiny tubs from princess auto. Petrobondforsale on eBay would be a little cheaper if it weren't for the border crossing involved (not to open that can of worms). If they would sell the binder for petrobond separately I'd be very happy, but they only import it pre-mulled.

The real P1 catalyst is propylene carbonate. I have most of a 5 gallon bucket of the stuff, but I usually just use a couple spritzes of methyl hydrate in the muller to reactivate mine instead. It's easier to get locally and if I spray in a little too much then excess will evaporate out before long and I can save my P.C., which doesn't evaporate out, for making new K-bond sand (homemade petrobond if. I can ever get my hands on the binder) or for mixing up core sand, since it's also a catalyst for sodium silicate binder. Using camp fuel for the catalyst is a new one on me, but if it works it works. Apparently there are a bunch of things that will work. High percentage isopropyl alcohol is another popular choice.

Jeff

 

[Tobho Mott]

Back from Foundry Supply Source (Formerly Smelko Foundry Products Ltd) in Milton ON with greensand ingredients and inoculant needed to finally give iron casting a try.

For cast iron, John P. (sales and sand lab guy from the supplier) gave me this recipe:

88% 56GFN sub-rounded silica*

10% bentonite clay**

2% seacoal***

Then mull with 3.5% of the total dry ingredients' weight in water.

* GFN (Grain Fineness Number) is a sort of average mesh size from a selection of screens used to describe foundry sands. The grain shape and the distribution of grain sizes has a fairly significant effect on the resulting molding sand's green strength. I tried making some with clean dry 70 mesh screened silica of unknown grain shape from a pottery supply in Ottawa several years ago and no matter how much clay (both bentonites) I added it never performed like the good stuff I bought from Tim Smelko in 2015 made with proper 130GFN Olivine and just 4-7% clay.

** I used 10% sodium aka western bentonite in the first 40 pounds of the new sand, intended to use as facing sand. It is more refractory than southern bentonite ie. should burn out less quickly in direct contact with the molten iron. The rest will have 5% western and 5% calcium aka southern bentonite. The southern bentonite gives greater green strength and lower dry strength (easier molds to shake out after casting). The 10% clay in this recipe is surprisingly different from the 4-7% clay in the old sand I bought. I assume that is because that was (angular grain shape) olivine and this is (sub-rounded) silica, so the grain shapes are different too, not just the obviously different grain sizes. If one sand has more surface area to coat with a thin layer of clay, then it would obviously need to have more clay added to get the same bond.

*** Seacoal improves "peel" ie. helps prevent sand from ending up stubbornly stuck to the surface of iron castings. Apparently it's a form of bituminous coal with very few impurities. I'm not sure whether it was actually plucked from a Scottish beach at low tide, but it sure is a big bag of coal dust. Generally not needed for nonferrous casting, but I did find that my old homemade greensand would stick to bronze castings until I added 1% coal dust from a local blacksmith's shop.

The muller is a modified cement mixer. I welded in a 1/4" thick steel wear plate for a floor and cut the tapered part off the top of the spinning drum, and attached a crossbar to the yoke. The wheel and plows are attached to the crossbar. It can make a 20# batch of greensand in about 10 minutes, or recondition half a 5 gallon bucket of used sand. I would be lost without it. The one at the supplier has a minimum batch size of 1500 pounds, which is why I didn't buy mine premulled.

Got parts for another cement mixer muller so I can avoid having to clean out one muller every time I switch from petrobond to greensand, but that can wait. The guy who built it bolted the crossbar to the legs instead of the yoke, so there's no way to dump it out yet.

Still have about half of my 500# of silica to turn into iron casting sand. Conveniently, the big orange barrel I got off kijiji is about halfway full. Another such barrel in the background holds all my petrobond for now. I'm going to have to rearrange the shed again to make room for these barrels or I'll forever be rolling them in and out of my storage tent!

(The little grey barrel has the facing sand in it)

The new sand feels great when I do the old squeeze test. Very sticky, yet doesn't stick to my hand. Already way better than my earlier attempt at a diy blend. It does feel more damp than I expected it to, even after a few days sealed up in the barrel to let the bentonites fully absorb the water. But 3.5% moisture should be dry enough to be "safe".

Foundry Supply Source has an awesome sand testing lab, John showed me all the instruments they use. There will be some video of that posted online eventually, with a little luck.

Jeff