To achieve optimum results the alcohol should be allowed to filter slowly through a long column of granular activated carbon.
1. The column of carbon should not be flooded with alcohol. The aim is for the alcohol to trickle through the long bed of carbon. As the alcohol flows and trickles across millions of grains of carbon incredible purifying takes place. So dripping the alcohol into the column gives best results.
2. The flow rate should be slow without stopping (approx 500ml per hour) or the effects are reduced.
3. The flow should take place through a carbon bed that is free of air pockets (this prevents channeling)
4. Alcohol should be no higher than 40% when filtering.