davidd's A Doll A Day Challenge 2020

[neon_jellyfish]

I'm pretty sure I've already mentioned this, so sorry about repeating myself, but be careful with storing them in plastic bags. They're more prone to getting devoured by mildew, and the plastic of the bag can (and if you give it enough time, it will) draw out the plasticizer from the doll, making it brittle and fragile. That's something that cannot be fixed once it happens.

Good tips. Thank you. 

But then... how can they be stored safely?

I'm afraid there's no ultimate solution that would allow you to just store them without additional care, but when it comes to 1/6 dolls like MH or Barbie, it's best to wrap them in acid-free tissue paper or kitchen roll (without colorful prints, of course) and store them standing in cardboard box with dividers for wine bottles (or for packing cups and glasses for moving). Even then you have to check for mildew every few weeks (more often if the place is humid), clean the dust, and now and then replace the tissue paper or the box. Constant care is a must whether you want to store your dolls away or keep them displayed. It's a high maintenance hobby, isn't it?

Edit: that box should have a lid, to protect them from dust. Also, it doesn't really have to be specifically a wine box, you can just use normal box and make your own dividers.
Another edit, because focus is my middle name: beware of the heat! I found that heat can cause yellowing even when the doll isn't ex™posed to light, especially if that doll has a glue seepage issue! If you can, keep them cool (you don't have to put them in the fridge, though)!