Quote Originally Posted by headshake
aren't the temps responsible for the difference in pressure?

-shake
Well yes; obviously. But the breaking is not due to the temps directly; it's due to the pressure difference. The temps created an increase in pressure. You could recreate the exact same situation without heat in a lab setting but I thought I would cite a real life situation a few of us may be familiar with instead.

is your new hobby mycology? that's a pretty interesting hobby.
Indeed it is my new hobby. It's pretty interesting and it's sort've like instant gratification. Mushrooms of all kinds seem to grow very quickly and it's fun to watch.

if so, isn't gas exchange necessary in mycology? won't stale air cause your cake to be slow colonizing or not to colonize at all? the tyvek is just used to keep the moisture out of your cakes while your pressure cook them. so the moisture content of the cake isn't messed with. (it's been a while since i read up on this stuff!)
yes and no.

Gas exchange speeds up the colonization of the spawn subtrate. Mycelium are like humans; they breath Oxygen and release CO2. CO2 inhibits the growth of Mycelium but it will still grow at an extreme crawl. Think of trying to grow cannabis in a tent with temps that are 95 degrees.

This is all relative to just Mycelium and not the actual technique used to create them. What you described is BRF Cake or a PFtek Cake. In those situations there is not really gas exchange to speak of because you pack the entire jar full of vermuculite and brown rice flour. However just because that is the technique does not mean it has anything to do with the mycelium growth process.

Many experienced mycology hobbyists will spawn to grain instead of BRF. The reason being is that 1 it colonizes faster (due to the gas exchange through the tyvek filter and because the mycelium can move around freely to spread faster) which allows less time for contamination in your substrate.

Here is what Tyvek is used for in Mycology:

*Keeps environment free of contaminants.
*Allows for gas exchange.
*Does not freely allow air into the environment
*helps to retain humidity levels.

It is also important to note that for the most part tyvek is only used to innoculate grains when they are in their jars. Once you put them into fruiting chamber your ventilation holes will be covered with polyfill instead of tyvek. Reason being is that polyfill keeps out contaminants/spores/etc etc... allows for gas exchange, helps retain humidity levels but most importantly allows fresh air in; unlike Tyvek.

I don't want to post links but if you do a search for tyvek and gas exchange you're sure to come up with some hits that will give you more insight into tyvek and I guess mycology (they seem closely linked).

Polyfill wouldn't work well for curing cannabis but Tyvek would be nice since it helps keep air out while allowing gas exchange.