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 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 while the vent is running. Doing so would circulate quite a bit of cool air through the kiln and this can crack the ware. 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 also help cool the kiln off.