How to make a cheap and easy tempeh incubator.
Supplies needed: 20qt storage bin, thermometer, weatherproof snap in socket, 40 watt light bulb, plastic junction box, electrical cord, non-breakable plate cover, steel plate and a dimmer switch.
Hardware needed: Wire clamp connector, 2 small bolts and corresponding nuts, electrical tape, duct tape, wire nuts (often supplied with the switch)
Tools needed: Stanley knife, drill, wrenches/drivers corresponding to the bolts used; tin snips
Remove the entire knockout on the side of the junction box that will be secured against the bin. Remove the appropriate knockout on an end, size corresponding to the clamp connector. Secure the junction box with the bolts/nuts, such that the side opening is approximately centered. Use the Stanley knife to cut away plastic around the opening, slightly larger than the hole, itself, or drill a 1.75 inch hole. Caulk the opening around the base of the socket.
Snap the socket through the cutaway on the bin, and into the junction box. Use a screwdriver to pull the snap-springs tight within the junction box to ensure the socket is firmly secured (the two, metal prongs that snapped into place – stretch them slightly further).
Secure the wire clamp, and then insert the power cord.
Connect the power cord to the dimmer switch, and socket. Follow the instructions that came with the cord and switch, but typically, the power source will either have a black stripe, or be smooth. Connect the white socket wire to the white, or ribbed wire, the smooth, or black-striped wire to the black wire on the switch, and then, the black wire on the socket to the other wire on the switch.
Note that this is a three-pole switch, because it was the cheapest one in stock. There is an additional wire that is not used, and that is simply capped. Two pole switches are all that are needed and will have only two wires.
Use electrical tape to secure the caps.
Secure the power cord. In this case, Romex sheathing was used to hold the cord securely. Electrical tape can be wound around the wire to give it the girth to be safely secured.
Secure the switch in place. Note that any exposed metal should be covered with electrical tape. That is, the back-side of the switch plate, in this example, should be completely covered with electrical tape.
The incubator is now fully functional. However… A few modifications were made after the trial run. The first was to shield the lid above the bulb. Several layers of aluminum foil and paper towel were used, secured with 2-way tape.
The other initial change was to hook the thermometer over the side, instead of using 2-way tape. I cut a thin strip of metal, bent it to hook over the edge, and hold the thermometer – secured, covered with duct tape.
A heat shield was also fabricated from the metal plate, to more evenly dissipate the heat, attached over the bolt ends.
The tray and rack were added in an attempt to avoid using plastic bags. The box was insulated using bubble packaging that the tray arrived in, along with some shop towel and more duct tape.
The setup kept the temperature very stable, starting out at 85F, quickly rising to 90F with full bulb output, then held steady at 89F at about three-quarters power. The first day it fluctuated between87F and 90F as we adjusted the dimmer, then, by the end of the day it had been honed in right where we wanted.
All in all it’s worked very well. The first two trials with just the tray (Credit for that idea, here), seemed to dry out on top, and the top was not fully ensconced. There were many variables changed for the latest, so it’s impossible to say with certainty, but laying a layer of perforated parchment paper over the tray seemed to protect the beans from over-drying.
Additionally, i stopped worrying about humidity altogether, and it doesn’t seem to have mattered at all. I changed the starter i was using – and the beans: The latest using garbanzos. Whichever or many of the reasons why, this last one had the best cake of any. (Outside of the plastic bags.)
There are many sites out there with instructions and suggestions. The basics are there: Soak the beans (2.5cups), hull the beans, cook the beans, and dry them well.
Then, it’s 2 tablespoons of vinegar and a teaspoon (Or, in the current case one packet) of the starter mixed with the beans.
Temperature in the incubator should stay between 85f and 90f, and i usually aim from right in the middle of that.
I gave up trying to incubate the beans on just the tray; found the best cake forms using perforated plastic bags. That has also improved the consistency in time it takes to fully form the cake, usually finished by 24 hours.
Per the advice of Betsy Shipley – and not seen elsewhere – I’ve taken to baking the cakes at 180F for 30 minutes to stop the fermentation process.