I have always heard that you definately want a good cake build in a briar pipe. The carbon is supposed to help absorb moisture as well as heat.
It's funny that this post came up as I was examining my Bjarne today which has a nice even cake which I can finally distinguish maybe 1/4 of the thickness of a dime. I only smoke Virginias and Va/Pers in this pipe period and have gone through about 3 ounces of that tobacco thus far.
In comparison my latika pipe Stanwell only gets smoked maybe 1/4 of the time that the virginia pipe is smoked and is building a cake much faster.
Obviously keep it reasonably trimmed but let that cake build....you'll have a much better smoker when it builds a little.
maboman
