This is an extremely easy to make yogurt maker that works really well.
-three outlet extension cord
-mini utility knife
-hot glue gun
This instructable is going to be a lot easier to follow exactly if you live near a Dollar Tree. You get one of their little foam coolers, three of their nightlights, and one of their extension cords. Actually, do yourself a favor and do not get a Dollar Tree extension cord. They are terrible. Spend a dollar or two more and get an extension cord that you can actually plug things into without having to widen the slots of the outlets. Be sure to get an extension cord that has the three outlets on the end of it. That is most any common, cheap 6 foot extension cord. Or get a longer extension cord if you want. The choice is yours.
If you don't live near Dollar tree, the theory that you must understand here is that you are making an insulated box and heating the inside of it with a certain number of watts of incandescent light bulbs to get it to within a temperature range that will work for making yogurt. So if you don't live near a Dollar Tree, look elsewhere for a small '12 cans plus ice' foam cooler and 8 to 12 watts of incandescent nightlight power to keep the inside of the cooler warm.
Step 3: 4 Watts or 7 Watts?
If you get the nightlights from the Dollar Tree, you'll notice that the package says the bulbs are 7 W, but the bulbs themselves say on the metal part that you screw in '120v 4W'. So are they four watts or are they seven watts? I don't know what to believe anymore. I'm inclined to believe the actual bulbs, what it says on them, which is 4 W, which is where I believe they really are.
The second time I made yogurt in this, I had somehow misplaced one of the nightlights, so I made yogurt using only two nightlights instead of three. That worked too. The three night light yogurt that I made the first time, I checked the temperature of it in the morning after having left it to incubated overnight, and it was right around where you want the top temperature range of yogurt to be, perhaps even 5 to 10°F above that. It was around 120 to 130° when I took the temperature reading of the actual yogurt. The yogurt was very solid with the significant layer of whey on the top. That is exactly how I wanted it to be for the purpose of making strained Greek yogurt. Yogurt can go two ways. You can go the fruit on the bottom/sweet/breakfast/ordinary yogurt way. Or you can go the hearty/salty/cheesy/dinner yogurt way. You want to use three nightlights and let it just go overnight, 8 to 10 hours if you are going for Greek yogurt. If you're going for normal yogurt, I would say use two nightlights and let it go 14- 16 hours. I'd like to have a little more heat and a little less time for normal yogurt, but then you're complicating the situation. You would need to either use three nightlights and add holes into the lid that could be uncovered or covered, or you could go to the hardware and buy a plug in lamp dimmer. I like the Greek style yogurt better. It seems to me like the less liquid way you leave in the yogurt, the better it keeps in the fridge.
I live in the United States. Here we have polarized electrical outlets where one side is longer than the other. To get the third night like to plug in your going to have to go against what the polarized outlet wants you to do. For me, I just had to push a little harder and the nightlight went in fine the 'wrong' way. I suppose you could give the third nightlight its own separate extension cord. The beauty of these 4 Watt bulbs, is that they really don't get hot, you can push them directly against the Styrofoam while at full power, and there is no melting/fire/fume hazard whatsoever, it just doesn't have the juice.
I did a test to see if a 15 Watt nightlight bulb would be a hazard. Even in direct contact with the Styrofoam,while the 15 W bulb did make it indent in the Styrofoam, there was still no fire/melting hazard. To be safe though, just don't lose the covers that the nightlights come with. Leave those on facing the bottom of the cooler so the bulbs aren't in direct contact with the Styrofoam cooler.
Step 5: The Chopstick Shelf
You need something to set your yogurt containers on, so they'renot sitting directly on the nightlights in a non-balanced falling over sort of way. You want a little table, shelf, stand, etc. A nice flat, level surface for the containers to set on.
If you don't have a whole bunch of glue guns and bags of chopsticks, first of all go get those things so that your life will be complete. Then make a stand like you see in the picture. You can cut the chopsticks with an awesome pair of Betty Crocker scissors from the Dollar tree, or any other pair of scissors that are not terrible scissors. The long chopsticks of the stand are just the length of the chopsticks. Running the other direction, the short chopsticks, I cut them down to a length of about 5 1/2 inches. Then the chopsticks stand just sets into the cooler. The cooler tapers at the sides, so at the point where the cooler is 5 1/2 inches by chopsticks length inches, the stand supports itself against the cooler walls. Nice.
The stand does not have to be made out of chopsticks and hot glue. Chopsticks and hot glue are just what I had on hand. You can use Legos, blocks of wood, cardboard, etc.
All right, so you pretty much done at this point. Plug the three nightlights into the end of the extension cord. Put those in the bottom of the cooler. The plug end of the extension cord will have to come up through the stand. So when you're making your stand, leave a little open space at the corner of it, big enough for the plug of the extension cord to go through. Take a look at the picture.
So once you got the nightlights and the stand in the cooler, you'll notice that the lid of the cooler doesn't fit on top because the extension cord is in the way. So you've got to cut a space for it in both the top of the cooler and the bottom of the lid. See picture. Then the lid will fit on nicely.
Just like I got a slot in the lid and the cooler for the extension cord to go through, I also cut a smaller slot for the wire of a thermometer probe like the one in the picture to go through. You can buy thermometers like the one in the picture off of eBay for less than two dollars a piece. Search 'digital thermometer'. You don't really need a thermometer, but why not? Unleash your inner scientist and measure something.
This step is a little short tutorial on how to make yogurt. Go buy a gallon of whole milk and a small container of either Chobani or Fage plain Greek yogurt. Okay, I guess any plain Greek yogurt will work.
With the right containers, you could make nearly a gallon of yogurt in this little yogurt maker. However big the containers are that you're using, you'll need to heat up that much milk, minus enough room to add a few spoons of boughten Greek yogurt to act as a starter.
I put the milk in a big glass stirring bowl and stick it in the microwave on high for about 10 minutes. Your shooting for 180°F. You're trying to take it up to just before boiling, where it steaming a lot. you want it scalding hot. I have my suspicions that you could just boil it and that would work fine.The microwave for me is a lot easier than the stove, because with the stove you have to keep watching it and stirring it, and even if you're doing all that is still always seems to burn on the bottom of the pan. So I use the microwave. Cancer in the long run? Probably. A lot easier in the short run? You bet.
Anyways, heat the milk to at least 180 Fahrenheit. This is where it's nice to have a thermometer. Once you've heated the milk, you've got to wait for it to cool down to 115°F before adding in the starter yogurt. Actually, the knowing when the milk is cooled down enough is the step that you most want to have the thermometer for. Once it's cooled down enough, then you add the starter yogurt. I use old yogurt containers and put a few spoons of starter in each one. Two fit easily in the cooler. Let the yogurt incubate 8-12 hours or so. Take a peek at it when you think it might be done. It should be nice and thick and have at least a little bit of liquid whey on the top. If you want you can stir the whey back in, I prefer to pour it off and have thicker yogurt. Good luck, any questions feel free to comment.
Step 9: Update: Another Easy/cheap Temperature Control Option
If you want to use a different cooler or bulbs. for instance if you already have a cooler and a light like a clamp light or a small lamp, here's a trick so you can use what you already have:
You modify an extension cord by adding in what's called a 'nc switch', which stands for 'normally closed switch'.
Pretty much you're making a magic extension cord that will turn your light bulb off when it gets the incubator to the right temperature and turn it back on again when it drops below that. Search this on ebay: 45c normal close
The 45c stands for 45 Celsius which is 113 Farenheit. That will work.