Petrobond is a trademarked oil-based foundry sand.
I have seen one alternative to it that can be home-blended/mixed with off-the-shelf ingredients, called "K-Bond", as follows:
I would add one note of caution about using oil-based sand with the hotter metals such as brass/bronze and iron.
If you open the mold shortly after pouring these metals, you will get a large plume of smoke that will often burst into a huge ball of flame.
I learned this by opening a hot mold, only to have a ball of fire in the face.
Luckily I saw it coming and closed my eyes (I had just removed my faceshield).
Don't repeat this error.
K-bond
K-Bond, named for Kent State where it was developed by one of Tom Cobett's Students, Is an almost smokeless oil bonded foundry sand.
It is used for casting zinc, aluminum, brass, bronze and iron.
The recipe is:
*100 lbs. sand - 100 mesh or finer
*6 lbs. bentone clay (such as Bentone 34 or VG-69)
*3 lbs. synthetic 2 cycle motor oil
*0.2 lbs. (3.2 fluid oz) Methanol (dry gas)
Mixing:
Mix the sand and bentone clay first (wear a dust mask!), then blend in the oil thoroughly.
Small batches (less than 10 lb.) can be done by hand with good results, but a muller is preferred.
The small batches can be done with a cheap kitchen electric mixer.
Add the alcohol and mix thoroughly.
"The sand won't seem like much until the alcohol takes effect and then it will become like stiff cookie dough.
How stiff?
It bogs down my muller!
It will be much easier to handle when it is a day old and will get easier to use with time and use.
The sand gets powdery after it sits and it is best to mull it or warm it before use.
When green strength starts to fade, add in some alcohol.
... Ray Brandes, quoted from his old web site. Also the source of this recipe.
The definitive source:
Subject: The History of K-BOND
Date: Wed, 13 Feb 2002 13:05:03 EST
K-BOND was developed in about 1995 at Kent State University.
The Metal Casting program at KSU had been using Petrobond for about 20 years.
We set about to find a suitable alternative to Petrobond.
After about 3 months of testing, we had evaluated many sources of bentone and many sources of "smokeless" oils.
(By the way, Petrobond is also made with Bentone.)
We found that virtually all organo-bentones will work well.
With this in mind, we bought the cheapest one we could find.
For the oil, we settled on AMOCO Indopol L-100.
This was listed as being a "food grade" material that burned cleanly.
Later, we found out that Indopol is the main ingredient of most smokeless 2-stroke oils.
The basic recipe for K-BOND is:
100 lb. of very fine silica sand (100 to 150 GFN)
6 - 7 lb. of Bentone (cheapest you can find)
3 lb. of Indopol L-100 oil
0.10 to 0.20 lb. of Propylene Carbonate (or Methanol or Isopropanol)
If the sand become too dry to mold, we add more Indopol.
If it lacks any strength, first we add more Propylene Carbonate.
If that does not bring up the strength, we add more Bentone.
We have used this stuff several times a week for aluminum, bronze and iron castings.
We have never thrown out the pile, we just add too it.
We don't get a room full of blue haze when we pour our molds.
We make castings that are incredibly smooth with extremely fine detail.
I am personally very pleased that some of you have taken the initiative to use K-BOND.
Dedicated to Metal Casting Education...
Tom Cobett
Cleveland, Ohio
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