Yes good idea....vertical chamber works OK ...but not too practical. So laying it over on its side is what I have done for years......I use a piece of 1" polycarbonate plexi....and liberally spray with parting agent....(Stoner Product...probably on the web somewhere) I can look up on the can and get you the right stuff....comes to mind Smooth-on sells some also and it is good....but costs a bit more for some reason......anther thing you can do instead of wax is use Vaseline...it isn't as long lasting with its residue...but does work.
I have one 35 gal (trash can size) and six 10 gal air tanks (paint pots) I have them mounted up in a shelf like affair and banded into position.....
Once you put the "shelf" affair in the tank....you have to level it up with a carpenter's torpedo level....do this after you have the tank and shelf deal all in place and then put screw type bands(automotive) strategically to hold the tank level. You'l have to work out what works best for you....But best for capacity is the tank on its side....for sure....especially fopr long molds.....the 35 gal one I have takes 24" plus long molds....
Like you I run up the pressure also.....just works better I think.....but I did for years just run in 45psi......that is adequete. For RTV....I run it up to 100psi in a 120 rated tank. Not saying its right...but it is what I do.
NOW....one thing....if you see a bubble....in the material.....you don't have to take the "lid" (plexi) off and start over......just carefully slide it over a bit and the bubble will "see" the escape route.....then slide the plexi back and your all set.
Remember ...the key is ...1. Overfill the mold........and 2. Roll the plexi on from one edge to the other.....hold it down until you can get a ....in your case........... a brick on it.
One last comment......don't "whip" the c1511 before you pour it........carefully stir it....bubbles in the material stay to a minimum this way.....don't shake it up in the can either. STIR it.....
Thanks ...glad I could help......
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----- Original Message -----
Sent: Monday, March 05, 2001 4:07 PM
Subject: [casting] Re: Smooth-On #C1511
I gave it a shot last night on a small flat mold and used a clear
piece of waxed plexiglass like I would do without the chamber. This
time I put in into the chamber, sat a brick on top and hit the
pressure(70psi), my chamber is rated for 80psi. I was pleasantly
surprised when there was not a bubble in sight...anywhere;-)
Now I know it works I can use it for those troublesome castings.
'Course my chamber is vertical so larger flatmolds won't fit. Guess I
need to do some redesign. I'm thinking of putting together a 4
chamber pressure system, horizontal with shelves so as one is
finished curing, I can refill and just keep rotating the molds.
Thankyou, kind sir.
Pacific Mountain Scale Shops
Mission, BC Canada
--- In casting@y..., "Rod Guthrie" <rod@r...> wrote:
> My method of casting flats with a backing plate .....and as you
suggest the possibility of trapping bubbles DOES still exist..THAT is
true....but I have done two things that minimizes the
possibility.....first is to use a clear plate that you can see the
bubbles if there are any.....completely (over) fill the mold...(waste
is inevitable) roll the plate to or from you to squeeze out all
excess materials AND and bubbles.....and then finally weight the
plate with blocks of lead (plumbing babbit)....... once this is all
accomplished, 45 pounds per sq inch of air is run into the tank.
(sometimes more) All of this only minimizes the possiblity of
bubbles.....but NEVER is a positive eliminator.....I'd say this works
about 80% of the time
> I have used this method for a fast cure....like Smooth-on
300.....and especially 305.
> With 300....you really have to move....and not do too many parts at
once...(which in a way defeats the "fast" pour purpose)....thus it
will work for fast set as well....but have everything ready and at
> Good luck! ROD
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