Does the Finish Affect the Smoking Characteristics of a Pipe?
The finish of a pipe has a modest impact on the way a pipe smokes, but it is a factor nonetheless. Smooth pipes, though most people find them to be the most attractive, tend to smoke hotter than other finishes. Rusticated (rough finish created with tools) and sandblasted pipes will smoke a bit cooler, usually.
The reason that the rougher finishes tend to be a bit cooler is two-fold. First, these finishes have more exposed surface area on the outside, which allows more heat to radiate out of the pipe. Also, especially in the case of sandblasted pipes, the rough finishes will usually remove some of the softer parts of the briar. The softer material tends to hold heat in more than the hard wood.
The bottom line is that since the effect is not all that great, and that there are other things can make a much bigger difference, a smooth or rough finish is no guarantee of a hotter or cooler smoke.