How to make a cheap and easy tempeh incubator.
Hardware needed: Wire clamp connector, 2 small bolts and corresponding nuts, electrical tape, wire nuts (often supplied with the switch), and 2-sided tape
Tools needed: Stanley knife, drill, wrenches/drivers corresponding to the bolts used.
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).
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.
The switch-plate cover may need to be modified (cut) to fit. Non-breakable covers are fairly simple to cut, by just scoring with a Stanley knife, cutting the curved ends, and then bending free. Make sure the back-side of the switch plate, beneath the cover, is taped off with electrical tape.
The incubator is now fully functional. However…
One issue that arose during the test run, was runaway humidity, as i wanted to use water to help moderate the temperature. I still think that’s a good idea, but some or all of the water would be better sealed in a hot water bottle or shallow container that could be placed in the bottom.
Despite some poor planning, total cost was under $30, far lower than incubators available, dehydrators that cooked at appropriate temperatures, and yogurt makers, the same. Some instapots have yogurt settings that are cool enough and, likewise, if you have an oven with an incandescent bulb, you can use that, presuming no one thoughtfully shuts off the light, overnight…
Travails, fails, but nevertheless – success
There’s a lot to improve on with this incubator, and the process, but despite concerns about the humidity, the proximity of the bulb, and a really heinous, last-minute, last-ditch construct of a rack just before running out the door, the first attempt at making tempeh in this incubator did, in fact, produce two perfectly edible, if misshaped loaves of tempeh.
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.
The laughable rack, made out of an old wire hanger, scrap wood, and painter’s tape:
As the boy would say: Oof. I’d hoped something around the kitchen would be suitable, but none of the cooling racks fit in the tub… So, this was the two-minute solution. Ugly and never to be used again, but it served it’s purpose – just to see if this contraption would actually work.
I don’t know if the proximity of the bulb would actually affect the end result, but after cooking beans in past attempts, this high-tech baffle was installed to protect the nearest corners. Initially, it was a flattened ‘V’, but unfolded and apparently levitated.
This was the low point of temperature and humidity. To combat the moisture, condensation was wiped from the sides, and one corner was propped open with a knife – straddling the corner to provide ventilation. Even with the lid partially propped open, temperature remained steady at 89F.
Improvements to be made are obviously creating a better rack, adding a ventilation valve to the lid, and more securely attaching the thermometer. Otherwise, this is a perfectly viable set-up for making tempeh, and much cheaper than moving to Indonesia.
And, one more modification that was always the weak-point of this design: Heat loss. As temperatures plummeted, it became more difficult to maintain the temperature needed. That was resolved by simply tossing a towel on the top. A more permanent solution was added using the bubble-wrap envelope that Amazon helpfully provided with the starter, shop towels and duct tape:
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, and i’ve found none exactly meet my experience. The basics are there: Soak the beans, 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.
Where the greatest variation occurs, is with the time it takes for the cake to fully form. Recommended times range from 22 hours, to four days! At 22 hours, my beans are still loose, and if i continue cooking them much past 36, I find the cakes start to spore.
Consistently, I’ve been concerned as i check the beans, that nothing’s happened. Then, by twenty-four hours they’ve solidified into a block. However, i don’t get a well covered block until closer to 36 hours (a little less, perhaps.) By 48, i start to get dark spots.