This came out in High Times Magazine last year.
Quoted from High Times March 2011 issue from the article "Trichome Tech - Inside the Resin Factory"
For years, K would harvest once the resin heads began turning from opaque to amber, but he's recently rethought his timing thanks to a study by Dr. Paul G. Mahlberg who found that the THC in a resin head is at its peak when it's still clear - not opaque and certainly not amber. Dr. Mahlberg stuck a tiny syringe into the bulbous head of the trichome and extracted its contents, then analyzed it for THC.
The result, without a doubt, THC is at its highest before the trichome turns opaque. This makes sense when you think about it: Who harvests fruit when it's turning brown?.....K now harvests at the first sign of opaque trichomes, when the majority on the plant are still clear."
But for years I have done what can be found below.
The capitate-stalked glandular trichome changes color as it matures.
Newly formed and immature glands are clear, glands reaching optimum THC production are cloudy or milky and amber trichomes have already passed their peak. By looking at the trichomes you can also determine the best time to harvest your plants.
When most trichomes have gone cloudy and a few amber ones have appeared, the plant is at its peak.
CANNABINOL (CBN)
Cannabinol (CBN) is the primary degradation product of THC and increases in concentration with plant age. The concentration of this product in the bud is heavily dependent on the time of harvest.
Harvesting the bud at a late stage also means that the concentration of CBN in relation to THC will be higher when compared to the peak of THC production.
CBN is only mildly psychoactive and can cause "fuzzy head", drowsiness, disorientation and sleepiness in the smoker, properties that can be considered unpleasant in nature compared to the clear high of the THC.
Done that already...
almost all r milky...
