2 PR-related questions

[jkeithrussell]

First:
http://www.finishsystems.com/resincastingpressurepots.html

Does anyone use the casting pressure pot shown here? It is pricey, compared to HF, but I wonder if it is better. I haven't bought the HF pressure pot yet. Mostly because I'm afraid it will be junk like everything else I've ever bought at HF.

Second:

How does this process sound to those of you who cast with PR: mix colors, pour into mold, place on vibrating scroll saw table, leave it there until an hour has passed; then, break out of mold and place in toaster oven at 200 degrees for another hour; then, let sit for 24 hours. Does that sound like a good system? I've done 3 or 4 castings that way and have gotten a lot of pin holes.

 

[skiprat]

I think that of all the people that cast in pots at least 90% of them use the HF ( or equivilant ) pot without any problem. I believe that the 10% that get problems are from operator error. ( Over tightening the lid, messing with the relief valve, abuse of the seal, leaking fittings etc.The one you linked to, seems to be the same Psi spec, but maybe with less capacity. I can't see any advantage for the massive price differance.

I think you answered your own second question:wink::biggrin:

 

[PR_Princess]

Keith,

For colored casts (sans embeds) I don't use a pressure pot. And while sometimes, pinholes just happen, using a vibrating table after you add in the catalyst may actually be contributing to your troubles. In my view, the vibration is causing bubbles to rise while the resin is setting and therefore they are getting "trapped" in the middle of the matrix.

But then.... I could be all wet too!:biggrin:

 

[jkeithrussell]

Well, I'm a bit stumped. Not just on the casting, but also on the pot.

I bought the HF pressure pot and replaced the fittings. On the smaller hole, I put an adapter, a shut off valve, and a plug/coupler for the air intake and release. On the larger hole, I put an adapter and a pressure gauge. I got everything as tight as I could and used a lot of teflon tape on all of the threads. I also put a little gasket grease on the gasket on the inside of the lid.

I set my air compressor to 60lbs and turned everything on. Went fine until it got to about 48-50lbs, then air started blowing out from under the lid. I stopped the air flow and left it for a while. It dropped about 2lbs of pressure every 5 minutes. I went back over everything twice, same result both times.

I guess I'm in the 10% group that can't make the pot work.

How much pressure is needed, and for how long? Any tips for tightening up the pot? You mentioned over-tightening the lid, but if I don't get it as tight as it will go with hand pressure, the air just blows right out.

 

[PTownSubbie]

Keith,

Don't get discouraged...... Mine started out the same way. I saw MesquiteMan's setup and tried that simplicity.
http://www.penturners.org/forum/showthread.php?t=40839

It worked with no leaks. I did it even simpler. I got rid of the dastardly leaky relief valve.

I have the gauge in the little hole with nothing else.

In the large hole, I put a shut-off valve and nipple. I pressurize to about 70# and let it stabilize. The rapid induction of air will caus some pressure loss until it stabilizes in temperature in the tank. I bump up the pressure a couple of times in the first 5-10 minutes and then I am good to go the rest of the night

Don't get discouraged though. You can make it work. The pot is no different than the expensive one you linked.......

If you need a pic of mine, let me know and I will take and post one.

 

[djwood1]

I am very interested in this thread. I WAS about to go to HF and buy a pressure pot. Only advice is make sure you use 6-7 rounds of teflon tape on every connection. Sounds like the lid sealing down is ALL of the problem though, right?

 

[dalemcginnis]

Keith,

Don't get discouraged...... Mine started out the same way. I saw MesquiteMan's setup and tried that simplicity.
http://www.penturners.org/forum/showthread.php?t=40839

It worked with no leaks. I did it even simpler. I got rid of the dastardly leaky relief valve.

NO, NO, NO, NO, AND NO!
Did I make myself clear. I am sick of reading people recommending that others eliminate the safety valve. If you want to risk your life and limb then fine! but don't recommend it to others! Now if you had said REPLACE the safety valve I would be with you as that is what I did with mine, but you said get rid of it. The valve is there for a reason and don't bother telling me about all the pressure gauges you have installed, you still need the valve.
Do any of you ever read the cautions that come at the beginning of any manual? Every one of them is there because some idiot did that.

 

[jkeithrussell]

I am very interested in this thread. I WAS about to go to HF and buy a pressure pot. Only advice is make sure you use 6-7 rounds of teflon tape on every connection. Sounds like the lid sealing down is ALL of the problem though, right?

Yes, it is. The air leaks out around the lid. I have sealed it tight, loose, and in the middle, and it leaks no matter what. I have carefully marked it to make sure that I'm putting it back in the same spot, but it leaks every time. I have gotten it tighter. I'm losing about 6 pounds of pressure over 5 hours. I've spent all day on it, and I'm pretty sick of it right now.

 

[seawolf]

I don't think you need to hold pressure for more than one (1) hour. If the resin is any good at all the re will not be any more resen pushed into the nooks and crannies after the first hour as the resin should be set up by then.
Mark

 

[rjwolfe3]

It's possible your pot is out of round. Not likely but not impossible either. I though I read a thread here last year about a pot that was bulged brand new out of the box.

 

[jkeithrussell]

After 24 hours of screwing with this thing, the best that I can do is an initial charge of 48 pounds (anything over that just blows out from under the lid). After 10 hours, it's at 36 pounds. There are no leaks on any of the fittings, and there is nothing apparently abnormal about the pot. My best guess is that the seal/gasket is a piece of crap, but it might also be that I'm just not capable of clamping down a lid.

Either way, I've done all that I can do and I don't know if the pot is useful. How much pressure is needed for PR casting, and for how long?

 

[PTownSubbie]

Just for the record. I didn't recommend he remove the relief valve. I just stated what I did. The relief was leaking so I removed it. If I can't control the pressure into the tank and remove the hose before I walk away, then I deserve what I get. I understand the amount of force that is inside of this tank when at pressure...... If I am careless, then I deserve whatever happens.....

NO, NO, NO, NO, AND NO!
Did I make myself clear. I am sick of reading people recommending that others eliminate the safety valve. If you want to risk your life and limb then fine! but don't recommend it to others! Now if you had said REPLACE the safety valve I would be with you as that is what I did with mine, but you said get rid of it. The valve is there for a reason and don't bother telling me about all the pressure gauges you have installed, you still need the valve.
Do any of you ever read the cautions that come at the beginning of any manual? Every one of them is there because some idiot did that.

 

[Klanham]

A bit on the HF pots - take the gauge off the pot and give it to the neightbor kids to use for a street hockey puck. That's about all mine was good for. I had similar problems that everyone else has described - leaking around the top - safety valve opening up - all at 45 PSI !! After trying everything else I wwent back into the compressor room and saw that while the gauge on the pot read 45 the gauge on my compressor output was at 85 !! I replace the gauge with another one I had in the storeroom - set the pressure on the compressor to 60 PSI and Voila! No more leaks, pressure holds good, safety valve is functional. Just my experience.

 

[bitshird]

I have a pressurized wax injector we use in making jewelry castings, I usually replace the seal once every 18 months, or it leaks, but of course it operates at a consistent temperature of 160 degrees which is hard on the seal. I found that I could but O rings from bearing supply stores that work better than the gaskets from the manufacturer and at a fraction of the cost, you might look for a company like Bearing Belt and Chain in your area for Large O rings to replace the seal., I wouldn't recommend removing the pressure relief valve though, replace it yes, you might not be the only one in the room if it were to explode.

 

[skiprat]

On the seal.
Remove the lid and very gently pry out the seal.
With a bit of Scotch Brite, clean the recess in the lid to remove any dirt and / or high spots ( paint or galvanising )
Rub the rim of the pot with the ScothBrite.
Clean the white powder of the seal ( if it has any ) and lubricate it with a thin coat of Vaseline if you haven't got access to proper o-ring lubricant.

For maybe the cost of giving away a pen, you can take the pressure relief valve to a decent plumber and he can calibrate it easily to open at the rated pressure ( or just below ). It is simply an adjustable spring loaded valve.
Some have rubber seats that could just need cleaning and others may have brass on brass seats. But like has been said, DON'T do without it:wink: