Casting help please!! Pressure or Vacumm??

[rblakemore]

I have read a lot of the threads and seen the videos!! My wife and I want to start casting. But I do not understand why pressure is really necessary for resin blanks (from what I see, I will start with alumilite) and "worthless wood". I have watched Curtis Seebecks videos and see the need for vacuum stabilizing (which I want to try!!); but, why doesn't vacuum work for blanks and worthless wood!!

 

[rblakemore]

Pressure today?!!?


My wife is helping a friend paint her house today and she has a CentralPneumatic 2.5 Horsepower, 21 gal., 125 PSI Cast Iron Vertical Air Compressor(with the tank) that her husband rarely used (unfortunately he passed 2 yrsago) and I think that I can obtain for about $100 or so. Is that goodenough to work with the pressure paint pot at Harbor Freight for about $100also?? This appears to be the pressure pot that most folks are using. The paint pot comes with a pressure sensing valve, so all that I need to add isa pressure relief valve (and an emergency valve??) and I am ready to go?!?! The compressor directlyconnects to the paint pot?? I see other uses for the compressor, likereal spray painting and cleaning. I have also inherited a small CampbellHausfeld PowerPal compressor from my father. Can that connect to the pressure pot also? I have just updated my check; and, unfortunately, I have the $$ for this. Iam tempted to get the compressor before it is gone.

 

[BSea]

That compressor should work fine. I'm assuming it has a regulator so you can adjust the pressure to the pot. There is a good article in the library on setting up a pressure pot.

 

[HamTurns]

I do not understand why pressure is really necessary for resin blanks (I will start with alumilite)

Pressure is used to collapse the air bubbles that are captured in the resin. Vacuum is not used because Alumilite doesn't have enough working time.

If you use the resin that Curtis suggests your working time is 7 minutes, that's not enough time under vacuum to get the bubbles to rise to the top before the resin sets. Keep in mind that 7 minutes is when you start to mix the resins, so by the time you get the resin into the pot you'll have much less time left, for me it's usually about 1 minute.

I use 60psi of pressure for my casting.

What I did with my pressure pot is to strip it down, taking all of the fittings off, and remove the draw tube from inside. Then I plugged all of the holes except one that I put a "tree" in. The tree is a three port "manifold" that has a shut-off valve being fed by a hose fitting, a pressure relief valve, and a pressure gauge. You will also want to add a right angle fitting to the inside as a diverter, so when you blow air into the pot it doesn't blow all of your liquid resin out of your molds.

The way I use it is to hook up the air hose with the valve closed, then slowly open the valve enough to get to 60psi and close the valve and disconnect the hose. I let the resin sit in the pressure pot for an hour.

The only thing the compressor needs to do is to get up to 60psi, so you don't need anything special as far as a compressor.

Happy turning
Tom

 

[Kenny Durrant]

I use pressuse to cast to help remove bubbles. I think the worthless wood casters use pressure to force the resin into the small cavities. You don't have the time to vacuum the resin and remove bubbles before it has time to penetrate and then set. As mentioned above make sure there is a regulator on the compressor along with a release valve on the pressure pot. The compressor I use goes to 125lbs and that stays consistant. The regulator on the compressor is so the pop off valve on the pot doesn't steadly spew air. Set the regulator for the pressure wanted in the pot and the pop off valve is for safety.

 

[TimS124]

If you're intending to pressurize your pot to 60 lbs, it's worth making sure you buy a pot that's rated at LEAST that high...

 

[Marko50]

If you're intending to pressurize your pot to 60 lbs, it's worth making sure you buy a pot that's rated at LEAST that high...

Yup. What he said.

Put your money into an American made pot. You won't regret it in terms of human life saved! If you're patient you will be able to find a heck of a deal on Ebay. I picked up a $500.00 pot for $60 bucks, made in the USA and certified to 125 psi.

I do mostly "tube-on" casting using Alumilite Clear. I almost never go above 25-30 psi. All I want to do is remove/crush the tiny air bubbles. The worthless wood and embedded stuff, yes, then I go up to 60-80 psi to make sure there is bonding and the resin flows into all the nooks and crannies. Always use a pressure relief valve in case you get into a run-away pressure situation.

Everything everyone else has said is excellent advice. Welcome to the addiction. :biggrin:

 

[rblakemore]

I need a little more help on this please

I need to keep this going a little longer please.
If I have a pressure pot, then why use vacuum for stabilizing?? Can I use pressure on the Cactus Juice??
The tank that I mentioned before is not holding pressure, it drops considerably in a few hours and is almost out of pressure overnight. It is a few years old and almost never used. Being new to a compressor - is this normal??
Will one of the little pancake compressors - 100 psi and 3 gallons - have enough power to pressure a 2 1/2 gallon paint pot??

 

[Jim Burr]

I need to keep this going a little longer please.
If I have a pressure pot, then why use vacuum for stabilizing?? Can I use pressure on the Cactus Juice??
The tank that I mentioned before is not holding pressure, it drops considerably in a few hours and is almost out of pressure overnight. It is a few years old and almost never used. Being new to a compressor - is this normal??
Will one of the little pancake compressors - 100 psi and 3 gallons - have enough power to pressure a 2 1/2 gallon paint pot??

This is why we have a Library and Search function....it's all there.

 

[BSea]

I need to keep this going a little longer please.
If I have a pressure pot, then why use vacuum for stabilizing?? Can I use pressure on the Cactus Juice??
The tank that I mentioned before is not holding pressure, it drops considerably in a few hours and is almost out of pressure overnight. It is a few years old and almost never used. Being new to a compressor - is this normal??
Will one of the little pancake compressors - 100 psi and 3 gallons - have enough power to pressure a 2 1/2 gallon paint pot??

I leave my pressure on for about 2 hours for both aluminum & PR (although I rarely use pressure for PR unless I'm casting stamps or something like that.).

You can use a little valine around the seal to help get a good seal.

Hope that helps.

 

[lorbay]

Because for stabilizing you need to remove all the air, so if you use punky wood to stabilize and you use pressure then you will end up with an air pocket at the centre, if you use vacuum then you pull all the air out and once the air is diminished and you release the vacuum the air is replaced with stabilizing resin. For using pressure you are usually have a tube in the mold or worthless wood and you are trying to reduce bubbles if any and therefore bonding the Alumilite to the wood or the tube eith minimum air bubbles if any. Hope this helps.
Lin