Re: Venting a cylindrical core
Posted: Thu May 17, 2012 5:23 am
Phew! Only a gazillion years ago, I promised to try again at the weekend. Shouldn't have opened my mouth just before the monsoon-season.
Updates:
A company in Bangkok sold me a kilo of Silica-gel for 100 Baht (3 dollars US), so I set about trying to dissolve it in Caustic-soda solution. I should have bashed it about a bit because those little beads took forever to dissolve. However, the end result beat sh*t-on-a-blanket. I'm impressed.
A quarter-cup of beads eventually went into the liquid, and amounted to about 400mL. I've been playing with it making cores galore and still have a 1/2 bottle left (and enough silica-gel for another two lifetimes.)
Last week, I molded a core for this darned cylinder but the weather turned bad so I left the core in my CO2 box overnight. Next day it had crumbled away at both ends, and totally collapsed when I touched it. Mai pen rai (Thai for No Matter) try again another day.
2nd attempt turned out quite hard but wet. Poured the casting, got a huge steam-bubble and a somewhat useless casting.
3rd attempt, today. Made the core yesterday, including a vent right through from end-to-end, left it in CO2 for an hour-or-two, then gently warmed it in the oven - 100C for 1/2 hour. This morning I re-heated the core, to 150C, while I prepared the rest of the mould.
While the pot was melting, I heated the core yet again so it was hot when I closed the mould and poured.
Beautiful (though I say it myself.)
I'll get the pics off the camera and post them tomorrow.
Geoff
Updates:
A company in Bangkok sold me a kilo of Silica-gel for 100 Baht (3 dollars US), so I set about trying to dissolve it in Caustic-soda solution. I should have bashed it about a bit because those little beads took forever to dissolve. However, the end result beat sh*t-on-a-blanket. I'm impressed.
A quarter-cup of beads eventually went into the liquid, and amounted to about 400mL. I've been playing with it making cores galore and still have a 1/2 bottle left (and enough silica-gel for another two lifetimes.)
Last week, I molded a core for this darned cylinder but the weather turned bad so I left the core in my CO2 box overnight. Next day it had crumbled away at both ends, and totally collapsed when I touched it. Mai pen rai (Thai for No Matter) try again another day.
2nd attempt turned out quite hard but wet. Poured the casting, got a huge steam-bubble and a somewhat useless casting.
3rd attempt, today. Made the core yesterday, including a vent right through from end-to-end, left it in CO2 for an hour-or-two, then gently warmed it in the oven - 100C for 1/2 hour. This morning I re-heated the core, to 150C, while I prepared the rest of the mould.
While the pot was melting, I heated the core yet again so it was hot when I closed the mould and poured.
Beautiful (though I say it myself.)
I'll get the pics off the camera and post them tomorrow.
Geoff