Originally Posted by Sleepdeprived12
hmmm, that makes a lot of sense actually, but now that makes me wonder if you had a sub 20" hookah if it would come into play or not. hrmmm...
From my own experience, I want to say it's somewhere between 20 and thirty inches. I've owned an 18 inch pipe that smoked pretty hot, and my 32 inch pipe seems to smoke cooly no matter if the water in the bottle is iced or room temperature.
To get scientific about it, you'd have to take into accout not only stem length, but stem bore and material, Water depth and temperature, Bowl material and style, tobacco type, coal type and number, hose type, length, bore, and material. Same for the hose's mouthpeice.
Would be interesting to see exactly how all these factors affect smokability, but I doubt anyone here really has the time/know-how/gumption to come to a realisitic conclusion.
My personal conclusions based on years of hookah experience are thus: Longer stem = cooler smoke, to a degree, however a maximum effective cooling length is reached somewhere around 30 inches.
A wider stem bore will result in a cooler smoke (Simple physics: Less pressure, less heat.)
When it comes to cooling, copper trumps brass as a stem material, brass trumps steel. Aluminum just plain sucks, as do galvanized materials (Such as I suspect Sahara stems are.)
Adding ice to the bottle may have a mild cooling effect, however this effect may be negated by the length and bore of your hose, as well as certain bowls or tobacco that just plain burn "hot". I've noticed that oftentimes my pipe will smoke just as cool without ice as with a ton of it. I presume this to be an effect of having 5+ feet of hose to travel through, the smoke has plenty of time to warm back up after leaving the cold bottle (which it spends a minimal time in anyways.) Chillers are the same way. The chiller itself may be cooled to extremely cold temperatures, but the smoke only passes that portion of the pipe for a fraction of a second. Leaving plenty of time for the smoke to re-warm.