Sizzle in the Bowl?

Hi John,
I get that in some of my newer pipes as well and I assume it is because my pipe isn't quite broken in yet. Sometimes you will hear that crackle as any moisture in the briar is heating. Again, this is only a novices opinion and assume others can give you a better answer, but I only hear that on my newer pipes.

+1 Yaz and Roth. It's not very uncommon, and could be caused by either tobacco or pipe.

I have a theory I am probably wrong but I have heard this as well from time to time. If that blend (Proper English) is anything like McClelland dark English 5110. It could be the texture of the tobacco burning. Dark English has the texture of a busted stump. You may be burning brush in your pipe

My briars tend to sizzle when smoking aro's, but my meers don't since I only smoke englishes in them. My englishes are drier than my aros. I've always believed that the sizzle was from moisture, and it sounds like I was right.

I really think more moisture in the pipe is condensation of the air as you smoke, than moisture released from the tobacco.
I have noticed that my pipe with a very small draft hole collects lots of moisture at the bottom of the bowl, and I can never smoke to the bottom. As soon as I hear that sizzling sound, and taste steamy smoke, I dump the bowl and call it finished. Doesn't matter what the tobacco is, nor the dryness level.

It usually doesn't matter how dry the tobacco is, as water vapour is a natural by-product of burning tobacco. It is interesting that you say this happens when you are not smoking the pipe. The same thing happens with me. My theory is that water vapour is condensing in the stem and draft hole. The upward pressure of drawing on a pipe keeps it there. But when you stop drawing, or if the moisture becomes too heavy, then it falls back in to the burning tobacco and the sizzle is that moisture turning to steam.
One way to minimise this, and it takes practise, is after every few draws of the pipe, is to give a very gentle blow back down the stem. This helps move moisture down into the burning tobacco to vaporize silently, before it builds up to the extent where it causes sizzle. This also helps keep the smoke drier, and helps smoking to the bottom of the bowl. Don't blow back too hard, do it gently, or you will blow ash out like Krakatoa!