Here is an interesting read on the subject, for those who have the time.....
The Thermodynamics of Pipe-Smoking
Thursday, August 5, 2010 at 6:32AM
Originally Posted Tuesday, February 7, 2009
A great deal has been written about how smoking technique changes the pipe smoker’s experience. While smoking technique seems to apply only to the strength and pace of draw, we know that a number of other variables also impact the experience: the pipe selected, chamber shape, the tobacco blend selected, and the density at which the tobacco is packed into the bowl.
Most pipe smokers focus first on their pipe and/or tobacco selection, secondarily on their tobacco-packing technique, and finally on tamping technique.
From my experience, however, the method by which the pipe is lit seems to warrant far less attention than other considerations.
One recent Saturday as I commenced lighting a bowl of G.L. Pease Stonehenge – a particular favorite of mine – when I reached for my old boy lighter I realized I had left it at home, so I asked my tobacconist for a box of wooden Swan Vesta matches. As I lit the tobacco, I was struck immediately by how different my experience of Stonehenge was upon my palate. This is a tobacco I know and love. It is one with which I have considerable experience, yet it tasted markedly different.
It is not unusual to have a favorite tobacco taste somewhat different from time to time. For example, I find that if I’m drinking espresso or strong black coffee that the first tobacco sip will yield a somewhat more subdued mix of flavors. If I’m drinking bourbon whisky, the taste will be stronger and more sugary. But this difference constituted an order-of-magnitude difference in flavor. There was considerably more sweetness and muskiness in the smoke. The sugars took on the typical smoky molasses quality found in Stonehenge, but the typical burnt caramel note I had come to expect was missing.
As I sat and wondered what was going on, I inspected the moisture of the tobacco. In a moment of epiphany, I realized that I had probably never lit this tobacco with a match as opposed to with my lighter. In that moment, I decided to experiment for a month or so by lighting my pipes solely with matches. I put my lighters in the drawer and I have been using matches exclusively since then.
I also decided to do some research on the science of igniting – or pyrolizing (as scientists call it) – tobacco. This little research project has taught me a great deal more than I bargained for.
First, I had no idea that my lighting method could impact my experience so significantly nor second, that thermodynamics would so clearly explain the differences in my experiences.
Not unsurprisingly, I discovered that medical researchers and scientists had been exploring the effects of tobacco burning temperatures on the development of aromatic carcinogens in tobaccos. Two Finnish scientists Ermala and Holsti published extensively on their research in the ‘50s. Their research compared and contrasted combustion dynamics in cigars, cigarettes, and pipes. Using thermocouple devices, Ermala and Holsti established that cigarette, cigar, and pipe burning dynamics are quite different from one another, despite the fact that tobacco is burned by the smoker in each of the delivery systems.
For example, pipe tobacco burns on average (in the combustion zone) at about 500 degrees Celsius. Cigarettes burn at about 670 degrees Celsius, and cigars burn at an intermediate average between pipes and cigarettes. With each smoking instrument, however, there is variability in temperature. For example, the maximum temperature a pipe smoker might achieve is 620 degrees Celsius whereas someone who has cultivated a slow, cool smoking style might smoke as low as 380 degrees Celsius. As you might surmise, this variability in temperature significantly impacts smoke temperature on the tongue, sensitivity of the palate, and most important, the actual flavor of the tobacco blend being smoked. How is flavor affected?
Ermala and Holst established that there are three zones in the pipe chamber:
“In principle, three main zones are distinguishable in burning tobacco (cigarette and pipe) : (a) the actual glowing point, where oxidation takes place, called in the following the “combustion zone,” (b) the “distillation zone,” where no actual glowing occurs but where the temperature is high and dry distillation quite strong, and (c) the zone farthest from the glow point, where the temperature is low and where, for that reason, condensation of dry distilled material can take place, and which is hence called the “condensation zone.”
As Ermala and Holst explained the dynamics of pipe tobacco combustion, they discovered that even at relatively low combustion temperatures the heat spread out in an extensive area outside the combustion zone (the actual glow point), and that within this heated area - the distillation zone - fractions of various substances (tars, oils, moisture) escaped into the smoke stream without being pyrolized. Ermala and Holsti noted that the distillation zone within a pipe is quite large. Further, a third zone - the condensation zone – produces condensation of dry distilled materials.
I realized as I studied this that pipe tobacco flavor is actually a blend of three processes, oxidation, dry distillation, and condensation. I further understood that the smoker’s ability to regulate smoking temperature would alter the proportions of the various three flavor-production processes. A “hot smoker” would produce greater numbers of oxidation (and presumably more distillate) flavors whereas a cool smoker would more likely equalize those proportions.
As I considered this information - and reflected on its implications with respect to my smoking style - I thought about my pipe-lighting style, and also my methods of tamping and relighting. It occurred to me that 1) I almost always used my butane pipe lighter to initially light my pipe; 2) that I have recently tried to manage the light in such a way that I achieved a large combustion zone (glowing area); and 3) during re-lights I have also tried to ensure that the tobacco is well lit in a large combustion zone, applying the butane flame for a considerable period of time.
When I compared the kindling temperatures of wood and butane, (in chemistry, kindling temperature is the lowest temperature at which a substance bursts into flame) I learned that butane, when mixed with air, burns at 1,977 degrees Celsius whereas matches burn between 600 and 800 degrees Celsius, depending on the wood variety used in manufacture (most matches use Aspen wood).
When I considered that there are still people who use butane torches to light their pipes, and that these devices produce temperatures of 2,500 degrees Celsius - the temperature of the Sun - I was flabbergasted.
Obviously, the differences in temperature are so extreme as to be almost absurd. As I considered the length of time I applied the butane flame to the tobacco, I realized that I was super-heating it, which could not help but impact the flavors, especially those sugary mature Virginias that I love.
As an aside, I also learned that Turkish tobaccos burn hotter than other varieties (The highest temperature recorded, 812°C., was in a Turkish cigarette.”) When I considered those tobaccos that are present in blends of which I am particularly fond – Orientals and Latakias – I concluded that it has been my lighting and re-lighting techniques that have produced the flavor distortions that I have routinely been experiencing for years. It became crystal clear why relights of the last 30 percent of the tobacco in a bowl often yields foul flavors upon relight.
My little research project has left me both wiser and happier. I am finding that my smoking experience has been enhanced by more careful attention to managing the size and intensity of my pipe’s combustion zone. I am experiencing more complexity in my tobaccos and considerably less tongue bite.
Further, I am more aware of my own moderation of my smoking style and how important it is to match tobacco density in packing with the engineering of the pipe being smoked. Those pipes with more open draws require denser packing and more modulated sipping of the smoke stream. Most importantly, I am now aware how important it is that I refrain from periodically super-heating the tobacco when I light and re-light.
As a postscript, like many of you, I’m sure, I have often wondered at the wild inconsistency and subjectivity of tobacco reviews. I now have a better understanding of just how much one’s choices, techniques, and tools impact a smoker’s perception of a blend.
http://www.apassionforpipes.com/classic-blog-posts/the-thermodynamics-of-pipe-smoking.html
