Alumilite clear - question

[Dale Allen]

I have tried 2 casts with this and in both cases I could not vacuum out the bubbles prior to pouring. I was able to do so with PR, but not this stuff.
If figured if the vacuum from the old foodsaver worked on the PR, it would work with this stuff.
I still get very tiny bubbles that you cannot see unless under a strong light.
I do warm the 2 resin parts in water prior to the pour but the bubbles just will not come out. With the PR, I could see it being de-gassed.
Would warming the resin more help? I use hot water from the tap and it is not hot to the touch. The resin is not like water when I mix so the viscosity could be better. I do warm the mold and the pours are hardening as expected. Just too many tiny bubbles.
At this point I am trying to decide if spending more money on a pressure pot is worth it as I am not doing very many of these and I suppose I could go back to the PR as that seemed to work. Wanted to get away from the smell however.
Thanks all for any help or comments.

 

[PTownSubbie]

Dale,

You are actually causing the resin to cure faster by warming it.....But if you don't warm it, the bubbles will be harder to remove...

That is why most people will tell you that you MUST use pressure when casting with Alumilite. The Champagne bubbles are too hard to get out before the resin hardens.....

Maybe someone else will have a better idea than pressure for you....

 

[steve worcester]

There are two different clear, water clear and clear. The water clear has a longer open time and longer cure, but also turns a bit better in that it doesn't shatter (chip) as easy and has UV inhibitors.
Both cast well using pressure, but I haven't tried casting without pressure.

Another helpful part is to pre-heat the molds and tubes. I preheat my silicone molds and tubes at about 120° for an hour. That helps a lot in the final product. It is more of an exact science to achieve the final results that we would like.

 

[Dale Allen]

Well, this isn't the first time I moved too fast on a new process. No harm done though. :biggrin: Fred, I see what you mean by accelerating the cure. The instructions indicate warming the part B if it is too thick. Well, I figured it couldn't hurt to do both. I actually had what seemed like plenty of time on both to move away the bubbles.
Sure seemed like it made some after the last time I looked!

And, as I now read further, the website says that you need to use pressure or vac to get '100% bubble free'!:redface:
So, what I am seeing is to be expected for the process I used.
Steve, I do heat the mold with the tube already set in it. But gee wiz, you really heat it up that long? Heck, I don't even like buying green bananas!:biggrin:

Anybody have a used pressure pot to sell?

 

[steve worcester]

...Steve, I do heat the mold with the tube already set in it. But gee wiz, you really heat it up that long? Heck, I don't even like buying green bananas!:biggrin:

Anybody have a used pressure pot to sell?

I heat it that long so that everything has leveled at that temp, comes from my glass casting days.
I use a Harbor Freight paint pressure pot and have pour some mold compound into the bottom to make it flat, but you could use a piece of thin plywood to do the same. I have also added a gauge and pressure regulator so I don't blow it up (a definite bad thing). You could also use the compressors regulator to limit the pressure.
HF has them on sale often.

 

[Marko50]

If you are patient and look every day, you can find American made pressure pots on ebay. I picked up a Binks pot for $65.00 this way. It gives me peace of mind knowing that the pot was certified and pressure tested up to 110 psi and manufactured 100% in the USA. It's built like a tank and I know it will handle the pressures I put into it. La Grange is also an American company that put out a hefty pressure pot that's certified. Patience and diligence are the keys to finding one!

 

[Jim Burr]

Patience and diligence are the keys to finding one!

You ain't kiddin'! Took me 8 months to find a great Craftsman, gun and hoses included.

 

[JD Combs Sr]

If you are patient and look every day, you can find American made pressure pots on ebay. I picked up a Binks pot for $65.00 this way. It gives me peace of mind knowing that the pot was certified and pressure tested up to 110 psi and manufactured 100% in the USA. It's built like a tank and I know it will handle the pressures I put into it. La Grange is also an American company that put out a hefty pressure pot that's certified. Patience and diligence are the keys to finding one!

What Marko said. I picked up an older American made one with a cast lid and five latches from eBay nearly identical to one I already have had for 30 years. I check for them there regularly and there is usually an old used one listed. Both of mine are 2.5 gal and I am kind of hoping to find a really cheap 4-5 gal.

Edit: Oh and BTW it is my experience that the curing process for A-clear actually generates bubbles therefore making pressurization mandatory for the process.

 

[Dale Allen]

Edit: Oh and BTW it is my experience that the curing process for A-clear actually generates bubbles therefore making pressurization mandatory for the process.

Oh my! Does Alumilite know this and is not saying so.
That would explain many things. It would also explain why they recommend that you de-gas with vac to get a clear pour.

 

[steve worcester]

Are you vacuuming then casting under pressure?

If you are, the vacuuming is an unneeded extra step IMHO. Pressure ate >40PSI will take out the bubbles depending on which clear and what the temp is. Higher temps and the resin cures faster and the bubbles can't escape. If you use water clear, you get a greater "open" time, but longer process time. But it isn't as brittle either.

 

[Dale Allen]

Steve, I've tried to vacuum it first but both methods I have at my disposal are not strong enough. As you said, it isn't necessary anyway. I use a 'pressure chamber' at 50-60 psi and I have no bubbles. I am just currently working through the learning curve of getting the resin to properly form a bond to printed the label. It is forming that often-seen silvery areas where it is not touching the label.
My clay blanks are working out fine now.