Flask lids melting

[This Side of Paradise]

I've just started using Magenta B-Caps as lids. During my pressure cooking cycle my lids are melting
Im cooking at 15lbs of pressure for 15 minutes.

Anyone else experiencing this?

[Ryan.Walsh]

Magenta caps are polypropylene which should be good to 135 c, at 15 psi the temp should only get to 121 c. I've never had a magenta cap (or the knock-off phytotech ones I use) melt or even look like it's melting so I would check your pressure valve for blockages. I have seen nalgene melt in an autoclave that was on the fritz, but once again it was at a higher pressure and temp than it was supposed to be. Under no conditions should polypropylene melt at 15psi/121c so it definitely sounds like a pressure cooker issue.

[This Side of Paradise]

I use a digital pressure cooker must be getting too hot.

darn guess im in the market for a new one

[Ryan.Walsh]

That's a bummer. Digital seems to be a hassle when dealing with pressure. The autoclave at the University I work at seems to be down for repair more often than it's working, and I as I mentioned, has melted expensive Nalgene labware. Honestly the old type pressure cooker with either a weight or valve will last far longer than a digital one. The All American brand, if you can afford it, will be something you can pass down to your kids it's that sturdy and well built.

[OCRC_Dir_China]

I am curious how much water do you find in the pot when you open it?

[This Side of Paradise]

about half of the amount i put in. I've used this pressure cooker for years but only ever used glass and metal lids

[Ryan.Walsh]

I think what OCRC_Dir_China was getting at was that if the pot water ran dry in the pressure cooker the temperature could easily get above 121c, however if there was still water in the pot when you opened it up this would tell you that this wasn't the case. This is very frustrating, I know. I hate when equipment malfunctions.

[OCRC_Dir_China]

If it still has an inch or so of water; then it most likely defective.

[Ryan.Walsh]

If it still has an inch or so of water; then it most likely defective.

An autoclave or a pressure cooker? A pressure cooker in my experience will most certainly have water let in the bottom after a 15-20 min cycle.

[Ben Belton]

I was going to say I've only had lids melt when I let the water dry up, but it looks like you've already covered this.

I will add though that THIS is the best autoclave pressure cooker ever. I have 2 of them. I cook in one while the other is cooling.