double filtering

[bdg77]

This is something that always seemed a little off to me. When using pre-sterilized/sealed vials, would the pressure inside the cooker not force steam (water) into the vials through the punctures created by the needles used to fill them? I know they basically seal off when the needle is removed, but there's still going to essentially be a hole/weak spot there for the pressure to equalize, no?

Or are vial stoppers really that good at self sealing? This study does seem to indicate they are pretty amazing, unrelated to pressure differentials though.

http://www.ncbi.nlm.nih.gov/pubmed/23636157

The purpose of the pressure cooker is to compensate for the build up of pressure in vial. So what your trying to achieve is equal pressure outside and inside the vial. Too much in vial and the seal may fail and top could explode. Too much outside pressure and there could be the possibility of steam getting in. You basically want the vial to reach a certain internal temp and then let it cool. Excessive heat isn't good and could make compound break down quicker. If it were for personal a .45 filter and oven bake with a small pin to bleed pressure would be good enough for me. However in a situation where it needs to be capped and a pin hole would not be acceptable, that's where I think a pressure cooker could come in clutch. I'm sure there's a bit more to the process this than the simple explanations I've read. For example would you want to heat up slowly or put in once water is already almost boiling. I was thinking putting in a control vial of just veg. oil would be a good idea. That way you could open it and test internal temp.

 

[Docd187123]

This is something that always seemed a little off to me. When using pre-sterilized/sealed vials, would the pressure inside the cooker not force steam (water) into the vials through the punctures created by the needles used to fill them? I know they basically seal off when the needle is removed, but there's still going to essentially be a hole/weak spot there for the pressure to equalize, no?

Or are vial stoppers really that good at self sealing? This study does seem to indicate they are pretty amazing, unrelated to pressure differentials though.

http://www.ncbi.nlm.nih.gov/pubmed/23636157

One or two punctures will not be an issue for a good multi-use stopper.

 

[Docd187123]

also doc, can you provide maybe some visual aids on how this pressure cooking technique is done?

I don't have any pics. The pressure cooker I bought came with a stand. Fill a few inches of water and put the stand in. Put vials on stand. Vials should not be submerged in water at all. Close off and once pressure is reached cook for 1-2hrs

 

[Docd187123]

The purpose of the pressure cooker is to compensate for the build up of pressure in vial. So what your trying to achieve is equal pressure outside and inside the vial. Too much in vial and the seal may fail and top could explode. Too much outside pressure and there could be the possibility of steam getting in. You basically want the vial to reach a certain internal temp and then let it cool. Excessive heat isn't good and could make compound break down quicker. If it were for personal a .45 filter and oven bake with a small pin to bleed pressure would be good enough for me. However in a situation where it needs to be capped and a pin hole would not be acceptable, that's where I think a pressure cooker could come in clutch. I'm sure there's a bit more to the process this than the simple explanations I've read. For example would you want to heat up slowly or put in once water is already almost boiling. I was thinking putting in a control vial of just veg. oil would be a good idea. That way you could open it and test internal temp.

You should never bake your gear.

The purpose of the pressure cooker is to raise the boiling point of water so the steam is hotter. Wet hear penetrates most substances better than dry heat.

 

[bdg77]

You should never bake your gear.

The purpose of the pressure cooker is to raise the boiling point of water so the steam is hotter. Wet hear penetrates most substances better than dry heat.

Yeah, you have a point. That's why I'm interested in getting the pressure cooker method figured out. Got a pretty good one I think. The brand is fagor, but it doesn't have a pressure meter on it. Do you have to guesstimate or what?

 

[Docd187123]

Yeah, you have a point. That's why I'm interested in getting the pressure cooker method figured out. Got a pretty good one I think. The brand is fagor, but it doesn't have a pressure meter on it. Do you have to guesstimate or what?

No the box/instructions should have it listed or look the model number up and check.

 

[fightingfires]

pressure cookers raise aprox 15lbs in order to get the temp on the gage to 250f
thats a huge part of their appeal. They take water past the point of boiling and release the steam at a controlled rate to maintain 15lbs of pressure.

If 15 lbs is pushing water into your vial more than likely the crimp is not enough on the cap rather than the tiny hole made by filling it.

 

[fightingfires]

couple other facts to consider...
oils have very little expansion compared to air or water, and oils expansion really only occurs after it hits its boiling point.
so an oil filled vial in a pressure cooker...its contents expand very little other than the air within the vial. There should be no loss of any contents at all from expanding through the vial stopper.
As the pressure cooker cools, the pressure reduces. I never even allow it to get cooled off though....what I do is simply turn off hear and allow the cooker to drop below the water boiling point, then lift the stopper/shaker on the lid till the pressure equalizes and then the cover can be removed safely. I take out the still very hot vials and set them on the counter to cool on their own
this further lessens the chance of any water ever contacting the inside (not that there is really even the chance)

 

[bdg77]

couple other facts to consider...
oils have very little expansion compared to air or water, and oils expansion really only occurs after it hits its boiling point.
so an oil filled vial in a pressure cooker...its contents expand very little other than the air within the vial. There should be no loss of any contents at all from expanding through the vial stopper.
As the pressure cooker cools, the pressure reduces. I never even allow it to get cooled off though....what I do is simply turn off hear and allow the cooker to drop below the water boiling point, then lift the stopper/shaker on the lid till the pressure equalizes and then the cover can be removed safely. I take out the still very hot vials and set them on the counter to cool on their own
this further lessens the chance of any water ever contacting the inside (not that there is really even the chance)

Oh, Ok so really it's the air inside causing the pressure. Well heck all the more reason to fill those vials up. I think this could work.

 

[fightingfires]

great way to prove it to yourself if to put some oil into a measuring container and then into a pot of water. Raise the temp on the water to boiling and take a look at the amount of oil in the measuring container. You will see it barely budges at all...so little that it is probably far less than 1%

air on the other hand expands massively....from 20C (roomish temp) to 40C it will increase in volume 6% That's in just a 20C jump
Imagine the increase in an 80C jump up to water boiling temp

 

[Jeep187]

From what I've been reading it seems that all cooker go to 15psi. I think it's the standard. For anyone still trying to figure this out

 

[Docd187123]

From what I've been reading it seems that all cooker go to 15psi. I think it's the standard. For anyone still trying to figure this out

I've seen a few that went lower here in the states and a friend in Europe has a hard time finding any 15psi ones.

 

[MEEKmlz]

U can find 15psi ones here in europe but they are expensive as fuck. I know at walmart in america u can get them super cheap. I used to grow mushrooms haha and u need a pressure cooker for that as well. But same concept. Pressure cooking to eliminate all bacteria. But this thread answers a few questions I created on another thread.