Final answer:
The doubler increases the alcohol content of moonshine by re-condensing and redistilling the alcohol vapors, helping in further purification and boosting the potency.
Step-by-step explanation:
The doubler in the moonshine process plays a crucial role by increasing the alcohol content of the moonshine. This is accomplished by collecting the alcohol vapor that comes off the first pot during distillation, and then re-condensing and re-distilling it.
Essentially, it acts as a second distillation phase, which further purifies the alcohol and boosts its potency, as more impurities with lower boiling points are separated from the alcohol.