There's a few specifics about drying that lead to a plethora of questions when proceeding with a cultivation project and I'm going to cover them all here, in a reasonable order, free of any information that hasn't been peer reviewed on the forums by thorough and learned cultivators. Let's start from the beginning:
Q:) Is drying mushrooms necessary?
A:) For long term storage, absolutely. Fresh mushrooms can be stored in a paper bag in the fridge for about a week or so before showing noticeable signs of degradation. For mushrooms that must be stored any longer, they must be dried to avoid rotting, potency loss, or worse. (there is worse than that, trust me)
Q:) What drying method should I use? A:) For most this is an easy question to answer. A food dehydrator at the highest temp it will allow is hands down the best way to dry mushrooms if you have one available. If not there are a few alternative methods you can use, namely placing them in front of a fan for about 48 hours and then storing them in a sealed container with desiccant (silica gel packs work well) to dry out the rest of the way. You'll want to make sure that they are very nearly "cracker dry" when you put them in with the desiccant, because the primary function of desiccant is to keep things dry, not necessarily to dry them out. Another thing you can do to dry them a bit faster is to place them on a baking sheet, set the baking sheet on your fully open oven door, with the oven on about 200F, and have a fan blow air past the mushrooms, into the oven, which will cause an outpour of warm flowing air where the mushrooms are resting, drying them much more quickly and effectively than a fan alone. These will still need to be stored with a small desiccant packet in a sealed container most likely.
Q:) I keep hearing "Cracker dry". What does this mean specifically? A:) "Cracker dry" is a term used to describe mushrooms that have lost 100% of their water content. They cannot get any drier. The easiest way to test this is to attempt to bend a mushroom's stipe(stem). If the mushroom is completely dry, it will simply break under pressure. If there is any moisture left it will bend, to varying degrees. A mushroom that was bent many times prematurely may be misleadingly "bendy" when they are cracker dry, but you will still be able to tell by applying pressure to the largest mushroom in the drying batch. They take the longest to dry, so if they are cracker dry, you can count on the rest being that way as well. Mushrooms that are cracker dry before they are stored away will not need desiccant, but it can still be used for peace of mind. Mushrooms that were fan or oven dried will still require testing for cracker dryness after a few days in the sealed container with the desiccant.
Q:) How long will x amount of mushrooms take to dry? A:) This is never a simple question to answer but there are certain minimum times that are good to start with. For 200g fresh or less, about 8 hours in the dehydrator is often enough to do it. That's more like 16-24 with the oven trick and 24-32 with the fan. For more than 300g fresh, depending on the load capacity and how you arrange them, they could take from 12-24 in a dehydrator, 32-48 with the oven trick, and 2-3 days in front of a fan. After that amount of time I'd do the dryness check. Usually after I've found them to be at their peak dryness I'll continue drying them for another hour or so just to be sure.
Q:) How much weight will I lose after drying? A:)Mushrooms are about 90% water on average. You could have anywhere from roughly 8-12% of your original fresh weight in dried weight, depending on if the mushrooms had taken on additional water or were over-misted.
Q:) Okay I have mushrooms in a sealed dry container, where do I put them so they last the longest? A:) It's often perfectly acceptable to just leave them in a drawer or wherever you'd most like to be able to access them from, but for extremely long term storage, they can be placed in the freezer inside of their airtight container. Since they are 100% dry they won't have to thaw and any oxidation that could be occurring would of course be slowed significantly. Otherwise, any "cool dark place" will work fine. If they survived the dehydrator run they'll survive your sock drawer.