Necessary supplies: 3 liter bottle perlite scalpel peroxide Kevlar gloves or tough gloves
3 liter bottles
Use a scalpel to CAREFULLY!!!! poke a hole right above the label and then cut around as straight as possible. If it is cut too short then it will not hold itself up and if it's cut too long it will be too tight so right above the line is best. Use cut resistant gloves made with Kevlar if possible and hold the scalpel away from your body. A scalpel injury can be very serious! You can try a sharp knife but it's a lot harder to make it straight with a knife.
Test it to make sure it fits right. The top should fit snug on the body of the bottle when put straight.
Soak some perlite in pure 3%hydrogen peroxide then cover the bottom of the bottle with it enough to level with the bottom of the label.
Place a colonized cake upside down or right side up (as you wish) in the center of the bottle.
Cover it back up and label it. Place in a lighted location. Even outdoors is fine. Make sure it doesn't get direct afternoon sun. Indirect light is best.
This method works great. Sometimes it even works better then some more complicate methods that can be used. It has a built in humidity and air exchange regulator. The air exchange regulator is the cap of the bottle. You may want to keep it completely closed when you are trying to increase humidity rapidly. Losen it to keep humidity rising at a steady pace or keep it all the way off for the maximum amount of air exchange. The design that the bottles have with a skinnier top causes a force that pushes fresh air in and C02 out automatically and naturally. You can further control air exchange and humidity by pushing or pulling the top part of the bottle further down or further up. It can be placed right above the cake or all the way on the very top of the body. To fan quickly tilt the top part of the bottle sideways a little bit to loosen and pump the top up and down the body of the bottle rapidly just as if you were using a pump. Careful not to hit your cake.