The Fermenter

A polypropylene laundry tub makes an ideal fermenter. A common size is 45 x 50 cm by 30 cm deep, standing on four legs to give a total height of 85 cm above the ground. The working volume is about 65 litres or 17 US gallons.

One can make this fermenter as simple or as elaborate as one wishes. In its simplest form one would merely close the drain-hole with a rubber stopper, add the sugar and dissolve it in warm water, add the yeast and stir periodically. This presumably is how they made "bathtub" gin in the old days, using a bathtub instead of a laundry tub. But for convenience and to get the best yield of alcohol a few refinements should be added. One is a cover to keep out dust, any insects flying around, and to reduce losses by evaporation and oxidation. Another is an electrically driven stirrer. A third is a heater to maintain the right temperature over the several days of fermentation. A fourth is a faucet attached to the drain to permit the beer to be run directly into the stripper (see below) and wash water to be directed to the house drain when the fermenter is being rinsed out.

A suitable arrangement is shown in Figure 1. The fermenter stands on four legs which in turn stand on four cement blocks. The purpose of these blocks is to raise the bottom of the laundry tub to a point where all the beer can be transferred to the beer-stripper by gravity flow following fermentation.

Cover: A cover for the laundry tub can be made out of either thick sheet plastic or plate glass. The plastic is easy to work with but suffers from the disadvantage that it bends up at the edges as the high humidity in the fermenter expands the underside of the sheet. For clarity in viewing and stability in operation plate glass about H inch thick is ideal, albeit difficult for an amateur to work with. A laundry tub usually has a convenient shoulder a few centimetres below the top so have your glass supplier cut a piece to a size which will rest comfortably on this shoulder.

Two holes should be drilled in the cover, one in the centre about 1/ inches in diameter to take an immersion heater and the other about 5/16 of an inch for a thermometer. A small notch along one edge will be useful for accommodating the power supply line if you intend to use a submersible circulating pump (see below).

Stirrer: There are at least three methods of stirring the fermentation brew. They are: a) with a motor mounted above the fermenter driving a shaft which goes through a hole in the glass cover-plate; b) with an impeller mounted through the bottom of the laundry tub. The impeller in the base of a food blender can be adapted to this purpose; c) with a submersible pump such as used for circulating the water in an aquarium or for driving the fountain in a small ornamental pool. Our strong recommendation is to use a submersible pump, the reason being that the shaft of a stirrer mounted as in a) above tends to whip while a stirrer mounted in the bottom of the tub as in b) above tends to leak. A submersible pump on the other hand suffers from neither of these two disadvantages. If you use an aquarium pump, be sure to close off the air inlet provided for the aeration of the aquarium since

Fractional Distillation Fermentation

aeration during fermentation will simply lead to the growth of yeast rather than to the production of alcohol. Alternatively, submerse the pump sufficiently deeply in the beer that no air can reach it.

Immersion heater: The optimum temperature for fermentation is between 30 oC and 35 oC. Fermentation itself generates some heat but probably insufficient to maintain this temperature, particularly if the room is cool. An external heat source should be provided, therefore, and since only 100 watts or so are required an immersion heater such as used for an aquarium is ideal. If it does not contain its own thermostat an ordinary light dimmer switch works very well. The immersion heater can be attached to a small piece of sheet plastic or metal and suspended through the large hole in the plate-glass cover.

Drain: The drain outlet of a laundry tub is designed to take a tailpipe for connection to the house drain. This should be modified to take a 3/4 inch ball-valve and hose adapter.

Use a brass tailpipe and some ingenuity(!) to connect it to the ball-valve. A length of hose with a female connection at both ends, as used for the hose connection to a washing machine, will enable you to couple the fermenter to the beer-stripper (see later) when you need to transfer the beer.

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