Pictures
open face mold at 50 and 100 percent alcohol
Keep in mind that the alcohol evaporates unless covered so this level is not a bad one to be at. The question is how well it acts in your molding.
Setup:The question is how much catalyst is really needed in a Petrobond 1 (Bentone 34) mix? To answer that question I mixed 2 lots of 25 lbs sand/ 1.25 lb Bentone 34./ .25 lb synthetic. The resulting fifty pounds was divided into 5 batches of 10 lbs each. The test was repeated on a 10lb batch of 70 mesh silica sand and 120 mesh olivine sand and worked up to 75% added methanol. Pictures are below the conclusion. The mixtures were to test various percentage additions of methanol catalyst as a percentage of the Bentone 34 weight. Percentages used were 1%, 5%,10%, 20%, 30%, 50%, 75%, 100%. I realized after the first set of that I was using fluid ounces and should have been using weight ounces so the first set of sand mixes used fluid ounces for the methanol and the second set of sand mixes used weight ounces for the methanol. An ounce of Methanol by weight is 75% of the fluid ounce. The difference is not noticeable in the small percentages. For this experiment, the alcohol was weighed on a triple beam scale and measured in a graduated cup. |
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Starting Recommendations:The manufacturer of the Bentone 34 suggests 33% by weight of Bentone 34 additive as the weighed amount of methanol catalyst. Web sources: 1% is the recommended amount |
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Conclusions:The 1% value is too little. Use at least the 33% as recommended by the manufacturer. I personally use no less than 50% and prefer 75%. The higher amounts give the same squeeze feel as a traditional green sand mix and stays in the cope/drag beautifully until shakeout. Also, if left uncovered the alcohol does dry out and you will need to add more to bring it back to a useable consistency. How much? add until it acts like it did when initially mixed and stay under the percentages by weight of sand for a new mix. So keep the alcohol on hand and keep the mix covered. I have modified the recipe on the site to reflect this and the need for longer mix times. |
| Percentage | Squeeze | Break | Comment |
|---|---|---|---|
| 1 % | |
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No green strength, lots of loose sand |
| 5 % | |
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some increase in green strength, lots of loose sand |
| 10 % | |
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some increase in green strength, less loose sand |
| 20 % | |
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a little better |
| 30 % | |
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this is getting reasonable, squeeze ball stays together, breaking is starting to clean up |
| 50 % | open face mold at 50 and 100 percent alcohol
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Nice impression of hand, little loose sand and breaks cleanly with some effort. Good lift off pattern and sand stays until shakeout. Does not feel 'clayey'. Starting to feel free alcohol if you have your hand in the sand. |
| 75 % | |
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good impression, good lift in the flask, stays together until shakeout, you can smell the free alcohol at this level. |
| 100 % | |
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Beautiful squeeze and break. Starting to get gummy feel, strong alcohol smell, disappears soon (evaporation or combining with Bentone). Good lift and shakeout
Keep in mind that the alcohol evaporates unless covered so this level is not a bad one to be at. The question is how well it acts in your molding. |