How to build a freeze dryer?

Question

Musing: If I use dry ice to freeze my specimen [achieving superior low temperatures] , and then place the specimen in the vacuum chamber and lower the pressure, have I improved/simplified or expedited the process?

Answer 1

Interesting approach. Let's see...what CO2 does is to act like a pump to remove water from the air
surrounding the material being "freeze dried". The Assuming the material is a plant, the plant tries to maintain an equilibrium amount of water vapor
in the vicinity of its leaves and stems. If the amount of water vapor decreases, the plant releases water to try to re-establish that
equilibrium. As long as the dry ice keeps freezing the water vapor, it is removed from the vicinity of the plant and eventually the plant "runs out
of water" and is freeze dried. It is not a chemical reaction that is dehydrating the plant it is "simply" a losing race with trying to keep the proper amount of water vapor around its foliage. So, as long as any dry ice remains, it will continue to freeze the water out and the plant will
continue to try to supply water in the form of vapor evaporated from its leaves to maintain the proper amount of moisture in its surroundings. In commercial processes the basic mechanism is increased by using auxiliary vacuum pumps as you mention (this greatly speeds transport of the water vapor from the "hot" region around the plant to the "cold" region of CO2 or even more
effective freeze drying agents such as liquid nitrogen, but the principles are the same. Also in commercial applications the temperature of the
substance being "freeze dried" is also decreased to reduce the amount of other components that might be frozen out. Specifically, in the case of
drying coffee the temperature is reduced so that flavoring components that are less volatile than water are not remove by the process...

Answer 2

Build A Freeze Dryer

Answer 3

You have to be able to pull a vacuum in a frozen environment, so you need a vacuum tight container that will fit in a freezer and the ability to run the vacuum lines out to the pump via a hole in the wall or past the gaskets or a vacuum pump that will start inside a frozen environment.

Answer 4

how alot of freeze dryers are made is by taking an old pressure cooker and turning them into freeze dryers. but all you really have to do is have a container that can hold a vacume, then it has to fit inside a freezer. pressure cookers make good freeze dryers because they are made to hold pressure, so they are good for negative pressure (vacume).

Answer 5

You have increased the thawing time.