This question gets asked a lot around the holidays. L&L's official line on cooling the kiln is leave it alone until it reaches 200F, then you can open it and unload it.
However, I have heard of all sorts of different cooling practices, and there are up and downsides to each. The upside is obviously a faster cooldown. The downsides are things like possibly cracking pieces in the kiln, possibly cracking the kiln's firebricks or lid/ floor slab, crazing (fine network of cracks) the surfaces of glazed ware etc. Here is how I was taught to cool the kiln back in school:
- First leave all the peephole plugs in until you cool off to about 1000F, at that point you can remove them. Put them somewhere safe and non-flammable.
- Put a non-flammable 1" prop (kiln post or better yet a chunk of firebrick if you have one) under the lid in the front of the kiln around 500F or 600F.
- Listen carefully for any pinging sounds. Pinging means the ware is cooling too quickly and that can cause crazing.
- If you use an under-the-kiln vent system you should not open the peephole plugs or prop the lid at all. When you open the peephole plugs and the vent system is on you are suddenly pulling quite a bit of air through the kiln and this can crack the ware near the peepholes. The kiln will cool off about 1/3 faster with the vent on anyway so if you use one you are already cooling the kiln off about as fast as you can.
- Having a floor mounted fan aimed at the kiln as well as good air circulation through the kiln room will help cool the kiln off as well.