A high-tar alternative to hashish (or buying more skunk) marijuana-resin consists of tar with a high concentration of THC. When smoking such, it is not advisable to hold in the smoke extensively, as the majority of the tar will be deposited in the lungs. One should remember that THC boils at 392 degrees farenheit; the hottest part of a butane bic lighter's flame will hit around 800 degrees.
When too hot of a flame is applied, plant matter will incinerate at the same time as THC and some crystals are absorbed by the produced tar. These crystals will stay "dormant" as long as the tar is cold. Whenever the tar is heated again, THC is released and stoning resumes.
This process also means that a LOT of tar is soaked into the lungs as it is heated and heated again, risk of cancer increases and lung capacity decreases.