machine#construction: casting#techniques: petrobond

Oil Bonded Sand  

aka petrobond

mulling techniques

  • Finer Detail, sharper corners
  • More forgiving,
  • Less likely to fail on you when turning and parting
  • doesn't "dry out"


  • Smoke and Fire. Yes it burns when you pour (It might not at the lower temps for ZA-X) doesn't always burst into flame for aluminum; always does for bronze. It will always smoke.
    • I seem to have a mild allergic reaction to the smoke, and possibly the sand.
  • It can be a PITA to work with after the first time. If you have a real muller this is a not a real problem, but if you need to do it by hand.......!
  • I find it a little more difficult to ram properly [But more forgiving of a bad ram]
  • Technically your used sand should probably be considered as toxic waste.
    • [IF the exact same components leak out of your oil pan, on to sandy dirt, it is considered no big thing. If I spill the exact same thing out side a transformer, that is a reportable toxic waste spill. Gotta love government regulation.]
  • Petro bond is "tighter", not letting air and gas pass through it as well. If you don't vent things right, you can end up with trapped air, which means a casting that doesn't fill.



Organoclay technology is what makes oil bonded sand work. Clays such as Bentonite and Hectorite are treated with quaternary fatty-acid amine to create the organoclay. This treatment changes the clay from hygrophilic to organophilic. Simply stated, the treated clay attracts oil instead of water. The amine may be applied to dry clay during grinding, or it can be applied to clay dispersed in water. The latter process is much more expensive, requiring filtering, drying, and other manufacturing steps. Foundry sand made with organoclay can be used to cast alloys of Magnesium, Aluminum, and Copper and Iron.


Petro Bond is a comercial product that uses organoclay technology and is manufactured by Bentonite Performance Materials. Petro Bond can be bought as a resin or a complete sand mixture. The resin (organoclay) is mixed (mulled) with fine grain sand, oil, and an activator. Since it uses oil instead of water, it needs less venting and can use finer grain sand than green sand. The oil creates considerably less gas than water. Petro Bond sand is reusable and can be rebonded. Petro Bond can be used to cast alloys of Magnesium, Aluminum, and Copper.


K-Bond was developed at Kent State University as an alternative to Petro Bond. K-Bond has several things in common with Petro Bond. They both use organoclay and oil to bind the sand. recipes


Petro Bond resin cost about US$30.00 from Budget Casting Supply. When you add in the cost of sand, oil, and activator, it is more than I wanted to pay. I couldn't find Bentone at a resonable price, or a supplier of Indopol that would sell me less than 55 gallons. I started looking for alternative materials.

I ended up substituting VG-69 (M-I Drilling Fluids organoclay) for the Bentone, and 2-stroke synthetic marine engine oil for the Indopol. I used Isopropyl Alcohol for the propylene carbonate. I made a 50 pound batch and poured several test castings (aluminum). The first castings were pitted due to gas, so I added more sand and VG-69 until I could pour castings without gas problems.

I have since found a supplier that will sell me Chevrons equivalent of Indopol in 5 gallon pails. I will also use propylene carbonate as the activator in my next batch of sand.


For anyone in the Pittsburgh, PA area, a source for a Petrobond substitute is Metco Supply Company in Leechburg, PA. Their webiste is:

Some fancy schmancy cast aluminum computer cases

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Last-modified: Thu, 14 Dec 2006 19:07:52 GMT (1489d)
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