I don't have a citation from a prestigious educational institution, but I've seen numerous references to caffeine having a half-life of approximately four hours in the human body. That would fit for the first four hours (13*4=52%), but after that, your formula doesn't fit with the half-life claim (at a flat 13% per hour, you'd be rid of it after 7.6 hours). With a four-hour half-life, after eight hours, your body still has 25% of the original caffeine level left.

Unless you mean that it's a logarithmic scale wherein each hour your body eliminates 13% of what's remaining, in which case, it's closer to the half-life idea (8 hours later, you'd have 32% of caffeine remaining).

This doesn't support your claim nor is it really a cite (how about a link?).

It's unclear to me if MDSD's post is trying to support or refute -DSH-'s assertion. Add me to the list of skeptics regarding -DSH-'s claim, it certainly doesn't jibe with my personal experience.

It seems like DSH got this info from a student homework sheet that mentions 13% in passing. :rolleyes:

http://www.google.com/url?sa=t&sourc...YhiVl1CP_oh-uQ

Yep :rolleyes::rolleyes::rolleyes:.

In the lesser class of joints I patronize most often, decaf may only be prepared in the pots with orange rims. Regular coffee made in such pots is automatically transubstantiated into unleaded.

In home environments, when the host(ess) offers offers coffee from a blue-dappled steel pot in which egg shells have been used to settle the grounds during boiling, chances are that the coffee is the super-caf sort, "ethyl".