Sand casting

IIRC--the petrobond was made by mixing sand with a cut-back asphalt,
then allowed to cure-(evaporate the solvent) then ready for use---
today they would probably use a waterbased emulsion (solvent much cheaper)
back when I wuz building county roads, there was a large area in the
county that had just the "right" sand for asphalt stabilizing. We'd cut
the sand up about 6" deep, windrow it on one side, drive a 5000gal
tanker down the road with a 3" valve open, dumping out a cut back
asphalt-about 60/40% with grader following and covering the "oil"
withabout 2 " of sand---usually took 5 or 6 truckloads of asphalt per
mile--Then it was bladed back & forth across the road until it was well
mixed and the solvent had evaporated...you could test it by grabbing a
handful , squeezing real hard , seeing how well it held its shape. You
could toss it into the windrow without it breaking.--Then if you dusted
off your hands & nothing stuck to them, it was ready to compact---made
an excellent base, which was then oiled & chipped a couple of times.
The reason for the Asphalt was that when dried back out--it was quite
rigid, .---some cheeapskates would sell a rural farmer a product called
tank bottoms- which was a parrafin like substance with some petroleum
left in it...this contimued to stay soft & lubricate the sand particles
so that they would never stiffen up--Same thing with used motor
oil--it's a lubricant, not a cement.
"course this was back when oil was $3 to $4 a BARREL---10¢ a gallon.
Reply to
Jerry Wass
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That wasn't petrobond - but casting sand maybe.
Petrobond is a trade name and it it a complex mix and is red. Mostly sand and rosin for the most part.
The rosin makes it sticky and flows when metal hits it. We used black sand when doing bronze, but the red will work but gets used up faster.
Martin
Jerry Wass wrote: > > IIRC--the petrobond was made by mixing sand with a cut-back asphalt, > then allowed to cure-(evaporate the solvent) then ready for use--- > today they would probably use a waterbased emulsion (solvent much cheaper) > > back when I wuz building county roads, there was a large area in the > county that had just the "right" sand for asphalt stabilizing. We'd cut > the sand up about 6" deep, windrow it on one side, drive a 5000gal > tanker down the road with a 3" valve open, dumping out a cut back > asphalt-about 60/40% with grader following and covering the "oil" > withabout 2 " of sand---usually took 5 or 6 truckloads of asphalt per > mile--Then it was bladed back & forth across the road until it was well > mixed and the solvent had evaporated...you could test it by grabbing a > handful , squeezing real hard , seeing how well it held its shape. You > could toss it into the windrow without it breaking.--Then if you dusted > off your hands & nothing stuck to them, it was ready to compact---made > an excellent base, which was then oiled & chipped a couple of times. > > The reason for the Asphalt was that when dried back out--it was quite > rigid, .---some cheeapskates would sell a rural farmer a product called > tank bottoms- which was a parrafin like substance with some petroleum > left in it...this contimued to stay soft & lubricate the sand particles > so that they would never stiffen up--Same thing with used motor > oil--it's a lubricant, not a cement. > > "course this was back when oil was $3 to $4 a BARREL---10¢ a gallon.
Reply to
Martin H. Eastburn
---------------- works well but is expensive. A clone is k-bond. click on
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note that Polybutane Indopol L-100 BP Petroleum or Chevron OLAO is a constituent in many HD 2 stroke motor oils. [Read the labels]
Also use "dry gas" as an "activator." (Methyl alcohol.)
The finer the sand the better the detail, but too fine and you start to have venting problems as the generated gas/air can't get through the very dense sand. You will need extra vents and possibly larger sprues and runners.
for detail possible see
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Reply to
F. George McDuffee

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