I have some tutoring in pressure canning, and an engineering background, so please don't judge me for what is about to be a naive question.

I understand that pressure canning uses a sealed liquid environment at higher than atmospheric pressure at 250 F for a measured period of time to create a sterile environment.

I want to pack small containers of food samples fully submerged in liquid in thier respective half inch cube closeable thin glass boxes (microscope slide thickness) stacked next to each other inside the jar, to occupy the space within the jar.

They would be separateable thusly so the flavors would not mix.

These cubes would occupy the nominal headspace limit of the jar, then the jar filled with water per jar requirements.

On other words, the ingredients of the mason jar would be fully but individual sealed.

The mechanism would be an electric pressure canner.


  1. Would the pressurized water bath properly heat the cubed through thier in glass envelopes?

  2. Would the mason jar do its job of maintaining a sterile environment until opened, just as it would if the ingredients were tightly packed?

  3. Would the heat and pressure conditions still transmit to within the contents of the sealed cubes, given sufficient cooking time?

The purpose is to make a bento-box in glass.

  • Hi, you seem to not be aware how food safety works. The questions you're asking are just a prerequisite for something being declared safe. The next steps have to be done by specialists, and involve doing risk modelling, gathering empirical proof that the food conserved this way really doesn't harbor pathogens, and then having an official body write up the method in foolproof terms and declare it safe. So, even if somebody here would know the answer to your exact questions and would tell you a confident "yes", that still wouldn't result in safe food.
    – rumtscho
    Commented Sep 11, 2023 at 11:08
  • 2
    I expect you're going to have a major problem with this scheme even before you get to "did it seal or not", which is that the interior glass containers will likely break. Pressure canning is pretty tough on the containers involved.
    – FuzzyChef
    Commented Sep 11, 2023 at 16:00
  • 1
    @rumtscho valid point and good to emphasize food safety concerns, but the question is not asking about food safety, but the physics of the setup. At least that’s how I read the question.
    – Stephie
    Commented Sep 11, 2023 at 16:35
  • @Stephie I also read the literal part as being about the physics only. I still suspect that the OP is concerned about the food safety and may interpret a "yes" or "no" answer as being equivalent to "is safe" or "is not safe", that's why I left the comment.
    – rumtscho
    Commented Sep 11, 2023 at 17:22
  • Well, they're not getting a "yes" or "no", so that won't be a problem.
    – FuzzyChef
    Commented Sep 11, 2023 at 17:34

1 Answer 1


Any container can be pressure cooked to recommended temperatures given enough time in the cooker. This may cause the food inside to become overcooked. But that's not your main problem with this setup.

When you're heat-treating a jar in a water bath, it is not completely sealed. Instead, the lid is just a little loose so that pressure, in the form of air, can escape. Then, when the jar comes out of the bath, one tightens the lid to form a tight seal.

It is clearly not possible to do this with a nested container. This means that the inner containers would either need to be unsealed (resulting in potential leakage into the other container), or would need to be tightly sealed before going into the pressure canner. Tightly sealed inner containers would have major issues with unequalized pressure between the inside and outside, particularly when they go above 100C. The "microscope slide thick" glass would certainly break, and might even explode.

If you think about it, you don't see commercially for sale foodstuffs packaged with both inner and outer canned sealed containers, and these problems are likely why. You're trying to solve an engineering problem that nobody in the industry has yet solved satisfactorily, so expect it to be very hard.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.