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Thread: Petrobond Problem Solving & Woes

  1. #1
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    Petrobond Problem Solving & Woes

    Okay Guys, Good news is i have gotten my Muller working. Works wonderfully all things considered. Now i got to mix a batch of petrobond, (Supplies generously supplied by BCS before they stoped offering it) simple mix.

    30 lbs Sand - About a 120 Mesh
    1lb 8oz Petrobond
    9.6 oz Petrobond Oil
    .4 oz Catalyst
    All was mesured out by weight.

    Now, This being my first time to use petro bond i am unsure if the formulation is correct. the material seems to lack the green strength i was thinking it would have. it just appears to have too much oil. So i add additional petrobond. with no change. I will see where it stands this afternoon. But until then Does anyone know what the problem could be? or if it is correct.
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  2. #2
    Senior Member HT1's Avatar
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    mull at least 5 minutes with just the sand and the clay, then add oil and catalyst and mull a full 11 minutes, that is the top of the green strength curve, you need more catalyst


    here is a good blurb credited at the bottom

    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.

    Petrobond II

    * 100 lb. dried silica sand
    * 5 lb. PETRO BOND II
    * 2 lb. PETRO BOND Oil
    * P-1 Catalyst not required

    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. (For Petrobond I) 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 (for PB1) and mix until it gets like cookie dough.
    (Ray Brandes)

    used Petrobond 1 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)

  3. #3
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    you have a photo showing the mixture, ratios sound about right, like HT1 says once you put the oil in mull it for ten to fifteen minutes and it will still have a oily feel to it till you get some use on it, but it should not be sloppy wet with oil.

  4. #4
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    Unfortuanately i don't like using my phone when my hands are covered in oil so no pictures. I will try getting some tonight.

    Its not a "Sloppy" wet feeling. more of a damp but more so then what my greensand normally is.

    That looks like the same recipe i was using. though i belive it is asking for more catalyst. I mulled the whole batch something along these lines.
    Sand and Petrobond(clay) about 10 mins.
    Mixed oil - 10 mins
    mixed catalyst. - about 10 mins.

    I was going to let it mull longer but before i could the power went out.

    Like i said i'm new to petro bond so this could just be me not knowing what i am looking at.

    HT1 / Dallen,
    Thank you
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  5. #5
    Senior Member Jammer's Avatar
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    I believe Murray always said to mix it well, it should be a little oily and leave it set overnight. The clay will continue to absorb the oil. Then mull it again.

  6. #6
    Senior Member HT1's Avatar
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    there is no reason to overmull, it is a waste of time and power, 11 minutes is optimal for petrobond
    your formula if you followed it closely is short on catalyst, which will cause the oil to not bond with the clay, and you end up with oily sand. you really cannot use too much catalyst, the excess will evaporate. unless you go complety crazy with it I suppose.
    it really should not get better overnight. though if you have a poor muller it might???

    Petrobond doesn't act well when it is cold. like below 50F mulling it will warm it enough to get it to act right though. this can be a problem if you let poured molds sit on deck in freezing weather, the sand will mull like lumps of clay, a real workout for the muller. you never want to work with sand that cold anyhow, real hard on the piddies



  7. #7
    Hello , everyone this is my first post on any forum in my life, I own a swif mul muller and follow the formula to the letter
    and make some excellent petrobond the rcipe from mifco in the manual is
    100lbs silica sand , 5lbs petrobond clay binder , 2 lbs of petrobond oil and 1 ounce of catalyst

    If you've browsed the net I'm sure you read you could use gas dry or heet as a catalyst . WRONG ANSWER
    you may substitute isopropyl alchohol however I just pay the premium for the right P-1 Catalyst and oil

    As for oil please do not use 30 wght non detergentoil it will work but poorly if you cant find the right oil you can substitute
    using 2 cycle marine oil.

    mix dry ingredients 1 minute add oil slowly mull 10 minutes add catalyst and mull additional 5 minutes youve reached 85 percent strength any longer not vwery beneficial I hope this helps anyone who wants to make their own petrobond

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