Rustication is the process of adding texture to the bowl and/or shank of a pipe. This is done to make an otherwise unattractive piece of briar look good. You will hear some claim that pipe maker "X" rusticates because he prefers that finish more than smooth. While perhaps true from an aesthetic standpoint, what I have trouble believing is that pipe maker "X" desires such a pay cut. In reality, a smooth pipe will sell for more than a rusticated one. Therefore, pipe makers are generally hoping to make a smooth, flawless, straight-grained pipe. The nature of briar doesn't allow that though, and rustication is a wonderful way of redeeming otherwise ugly briar.
Rustication can be accomplished with lots of methods. I will outline the few that I have used:
Typically I rusticate with a tool that was shown to me by Brian Ruthenberg. To add a bit to the history of this tool, Brian Ruthenberg told me he got this tool from Robert Vacher of Laughing Moon Pipes. I don't know where Robert got it. After looking at Brian's winning hawkbill in the P&T contest, I contacted him and asked how he did his rustication. He provided me instructions and photos for the tool he used. This tool is available at Home Depot, though some assembly is required. :-) Here's what it looks like:
To make this little beast, you will need a few 1/2" pipe fittings, some concrete nails, a 1/2" compression fitting with one end being a threaded male connection, and a bench grinder. The pipe fittings you need are a 1/2" threaded T, a 1/2" threaded coupling, and a 1/2" threaded nipple (choose your own length...I prefer a shorter one than that in the photos above. I have one that is 2" and one that is 4". I use the 4" one the most.)
I think assembly of the tool is pretty self-evident from the photos. I will just point out that the heads must be cut off the concrete nails, and the nails sharpened to a needle point on the bench grinder. You will also need to grind a bit off the sides of a few nails, or use fewer concrete nails and take up the slack with some small finish nails, in order to get the concrete nails to fit perfectly in the compression fitting.
To use the tool, simply press the tool (hard) into the briar and twist. The briar will pop off in chunks, leaving a random, craggy texture. The most common mistake when using this tool is not overlapping the "cuts" with the tool. Many folks have written me and asked how I got the results I get with the tool, as their rusticating looks sparse and unattractive. The answer is almost always, just do more!
Another method of rustication I have used is carving chisels. I have several chisels for hand carving, and I simply press the tool into the briar and pry off chunks. I am usually going for a deeper, more chunky look when I use these tools.
Lastly, the Dremel tool can be a great rusticator. I will leave this to you imagination, but suffice it to say that there are myriad bits and methods that will produce many beautiful textures.
Let me add in conclusion that a combination of the above methods can also be used to develop your own look and style of rustication.
Rustication information from pipemaker Tony Fillenwarth's site.