Petrobond I

PETRO BOND
* 100 lb. dried silica sand
* 5 lb. PETRO BOND
* 2 lb. PETRO BOND Oil
* 1.65 lb Methanol

Note that the Methanol weighs about .75 oz per 1 fluid oz.
It is recommended that all ingredients be weighed and the methanol amount is a starting value not a maximum value.
PETRO BOND Mixing Procedure
1. Weigh 100 lb. sand and 5 lb. PETRO BOND into the muller. Mull dry for 5 minutes.
2. Add 2 lb. PETRO BOND Oil (about 2 pints) to the muller. Mull 10 minutes.
3. Add 1.65 lb. Methanol. Mull 10 minutes. Sand is now ready to use.

In using a casting sand the key point is to get the clay or bentone to coat the Sand grains. That is part of the mulling process. Some have had good luck just using a mixer and paying attention to getting the resin on the sand. So another mixing procedure is:

Mixers from hand to cement mixers can be used. The Bentone is very fine and will make a lot of dust until you get the oil in. I suggest:
Until the last step, tape a sheet of plastic over the mouth of the mixser tokeep the dust in.
put the sand in the mixer
add the bentone and mix for five minutes
add oil and mix for about ten minutes
add gelling agent and mix until it gets like cookie dough.
(Ray Brandes)

used Petrobond can be reconstituted by adding 2-4 oz. of either proplylene carbonate or a mixture of 90% methanol and 10% water per 100 lb. of old sand (the water is absorbed by the alcohol). This will bring back the gellation properties of the clay. If you simply add more oil and you don't get the strength you wanted, that's a good sign that you need to add some of the "catalyst". Propylene Carbonate is the best, but hard to find in small amounts. Methanol is fairly easy to get as 'Heet' at WalMart or any auto store. It can also be bought by the gallon at a real paint store (not Home Depot or Lowe's).
(original form Tom Corbet, altered by Richard Kern)