To start you need to ferment the molasses. For proper fermentation you need to reduce the sugar content of the molasses by adding water to make a more manageable starting material for the yeast. High sugar content can inhibit the yeast from producing ethanol. The basic starting concentration should be less than 25% weight percent sugar. If the molasses represent 50% sugar, you need to add an equal amount of water to bring the sugar concentration down to 25%.
Once you've fermented the molasses you've created ethanol. To separate the ethanol, methanol and water, you need to distill it properly.
After this process is done, you can now add the fermentation wash into the still. You can use any of these stills to produce your rum:
Split top column alembic or our Double Boiler Spagyria model which we highly recommend for this type of distillation that allows for a more refined finish in your results. The distillate will have a higher percentage of alcohol in just one process. But you can use other types of alembics as well, simply refining the results and repeating the distillation process again to obtain higher grade results.
It's important to use an accurate thermometer. Accurate temperature measurement allows the distiller to collect a very specific range that contains the desirable components (i.e. ethanol plus flavor). The key is not to collect the methanol, which comes off the top of the distillation column (or pot) at around 64°C to 65°C.
The fraction you need to collect is between two temperature points. For rum production, you need to collect the part that comes off the still between 75°C and 83°C for light rum. Ethanol boils at 78.4°C, so it will sit at this temperature for a while before it starts to increase, but once the temperature starts to increase again you will need to watch very carefully and shut off the heat source once you approach 83°C. If you want to achieve a more flavorful rum you can collect everything up to about 90°C (the tails). Remember, don't keep anything that came out of the still below the temperature of 75°C, it's bad.