oil bonded sand.

[Kendall P]

Hi folks,

Im sat in my newly built forge, with some very cool resin blanks i want to sand cast with aluminium - and possibly later some aluminium/bronze alloy. Ive made myself my own casting flasks and im familliar with the methodology of sand casting. Here is my question.

Im a cheap skate (on a budget) and im wondering if its possible to mix my own small batch of home made "bodgers special" oil bonded sand that i can mix up to do some cheap experiments?

Have any of you tried to make something to this effect without the use of a mixer? - what ingrediants did you find worked best?

[Fe-Wood]

I looked for a recipe for bonded sand and didn't find anything that I didn't have to order. Then I came across about 300 pounds of regular petrobond.

I was planning on making mine in a 5 gl. bucket with a drill powered mixer. The kind used for mixing grout and the like. You can only make small batches at a time, about 1/3 to 1/2 bucket. Sounds like what you need.

A muller is the best but finding one is difficult. You might try the local school arts program. They may even have some sand you could have....

[HWooldridge]

Why not use water based sand? I'm no professional foundryman but have cast more than a few bronze hardware pieces and made up my own casting sand using water. Worked fine and no smelly fumes.

[Kendall P]

Well im casting some little mini sculptures and alot of casters rate it for its detailed surface finish over green sand. - Im just going by what ive read up - If i can get some bentonite clay cheap i can try both and see which mixture works best!

The drill bit mixer - i completely had not thought about - (total brain fart)

[HWooldridge]

I used bentonite, sugar sand (which is about 150 mesh), silica flour (250 mesh) and a small amount of crushed coal. I tumbled the mix dry first so the sand particles would coat then tempered it with water. This works fine for brass and bronze - it also gets better with use after it's mulled a few times.

If you still want Petrobond, get a copy of "Metal Casting: A Sand Casting Manual For The Small Foundry" by Chastain (volume 1 has the Petrobond recipe).

[Fe-Wood]

I believe detail is based on the fineness of the sand. Green sand we always used a fairly course sand when I did most of my casting. As with most cases of multent metal and moisture- make sure the green sand is dry or unrestricted as the combination can be- ah- interesting...

[OddDuck]

How fine the sand is depends on the particular metal you are pouring. For cast iron, you want a coarser mesh sand, say in the 60 mesh range or so. For aluminum, a 50/50 mix of 90 and 120 mesh sand is said to give the best balance in surface finish and porosity. For brass/bronze, this is where you need the finer mesh sand, 120 mesh and up. The finer the mesh, the more critical your venting is, The magic of greensand is that it is porous enough to allow the gasses created by the heat of the pour to vent out between the sand grains to some extent, and as the mesh increases the porosity decreases. An excellent read on this is the Navy Foundry manual. The nice thing about petrobond is that the venting problem is lessened considerably, so a finer mesh can be used with improved surface quality. The problem with petrobond and its variants is that you must use very specific ingreedients for it to come out right, and making your own can be a crapshoot. You also really need a muller to use it effectively, unless you want to throw away the burnt bits every time you use it. Oh, did I mention fairly expensive?
Greensand, on the other hand, is duh-simple and dirt cheap to use. No special equipment needed either, and reconstituting it means just adding a sprinkle of water and mabey a dusting of fresh bentonite. It's what I use, I wish my sand was a bit finer, I got it from a guy who did iron and steel, but it works okay with aluminum and bronze as well. As long as you are using the right range of mesh for the metal you are using, the finish should be comparable between the two. Pour temp is very critical to surface quality as well.
If you are still interested in oil-bonded sand, you may want to look up K-bond, recipies can be found on the web.

[ThomasPowers]

I picked up a couple hundred pounds of petrobond at a school auction once for $25; been using the good stuff for silver casting and have accidentally transferred a finger print with it several times. Gave away my muller when I moved though.

[781]

I watched a demonstration of tufa (SP) rock casting of fine silver.
The aleged proper way was to carve the rock only avalible in the SW indian reservation then pouring into this.
The demonstrator said he had friends that poured elaborate silver belt buckles and never had a bad casting. For years he kept asking how this was so until finally they let him into the back room were they were using oil sand made from dry powdered cement and 10 wt motor oil. The only tufa rock was a flat piece that made the back of the casting.

[ThomasPowers]

Tufa does work as does cuttlefish bone. Neither has as fine of a surface finish as a good oil sand. (and actually tufa is available in a number of places as it's derived from volcanic ash, not a rare item in the history of this planet...)

One site showing them using it is http://users.frii.com/dnorris/stonecast.html

Shoot I've cast silver in molds carved out of soft firebrick. (bad surface finish but it *cast* and clean up is part of the job anyway.)

[John McPherson]

Cheap bentonite clay = crushed (unused, please) kitty litter. An enterprising person ought to be able to rig a crusher and sieve set-up.

[JNewman]

One advantage of petrobond over green sand for the home caster is it takes much less work to maintain the sand. Green sand must have enough moisture to bond, but too much moisture can cause ruined castings or even explosions. If you don't use your green sand for a couple of weeks it will dry out. Re tempering your sand can not be done quickly if it has dried right out especially without a muller.

[Splinters]

Buy a tin of fullers earth it ready milled bentonite clay I have in my head that the mix is 1 part fullers to three parts silver sand then temper it with oil I am just looking into casting my self so am by no means an expert and am at work at the moment so dont have my notes I am just sharing what I have picked up asking about so far.

[rlbaker]

781, you just reminded me of something I haven't thought about in years, way back when we had a production casting shop for precious metals. All the casting was investment casting,lost  wax casting. About 20% of our business was hand fabricated production work and we made our own wire, tubing,plate etc and to make our wire we would use our biggest wire ingot mold, I guess it was about 1/2 or 5/8 square by maybe 8 or ten inches long we would pour a bar, go to the power mill,roll out the appropriate size and then transition to drawplates depending on cross section of finished wire. One year I had a guy work in the shop who was from a family of  filigree workers in Mexico. All these guys did was fine filigree work and he showed me how you could pour real long bars using cement mixed with motor oil, I had never heard of such a thing before, it worked great. If you are careful when you are making your wire with the low tech methods we used it is easy to get defects that dont show up until you have drawn your wire all the way down and started using it and then you can have some sharp edges that appear that can run the entire lenght of your wire, however many yards that is.Bad news, have to start all over. This Mexican goldsmith told me that when he was learning his trade as a small boy his dad would make him test his wire by drawing it across his tongue, you learn right away to draw quality wire that way!!

[Dan P.]

Years ago some idiot thought it would be a good idea to cast some aluminium into building sand mixed with old engine oil.

Unless you like the smell of burning dirty oil, and a workshop made unusable by being filled with smoke, I would avoid this method.

[doc]

The smoke problem is not an issue if you us synthetic 2 stroke smokeless oil. That is what is recommended for home grown K-Bond. 

[781]

Lost styrafoam inside the sand inside a building isnt too good either but I am sure someone somewhere is trying it as you read this post

[LeeMcKee]

Have you thought of using an investment type material like Ludo? Basically just have sand and half plaster. It works very well for non-ferrous metals. It is the traditional way of doing lost wax melt outs and it is very cheap... Good luck! 

[jack1knife]

I have recently been using DELFT Clay from the Netherlands I bout on RIOGRANDE dot com.

 

For very small models (other than the nasty fumes) the detail and quality is really unmatched for sandcasting.

 

Best of luck!

[njanvilman]

Years ago some idiot thought it would be a good idea to cast some aluminium into building sand mixed with old engine oil.

Unless you like the smell of burning dirty oil, and a workshop made unusable by being filled with smoke, I would avoid this method.

 

With proper ventilation, the smoke will dissipate in a few minutes.  I did aluminum casting in a school building for many years using Petrobond clay and 10w oil.  As we poured, it did produce smoke.  In under 10 minutes, the smoke was exhausted outside.  Never had a complaint or set off the smoke alarms in the hallways.  (We only had heat detectors in the shop).

[Frosty]

The most common mistake making home brew petrobond is using too much oil. A friend here who does a lot of bronze and some iron casting uses resin bonded the smoke is almost nil.

 

Frosty The Lucky.