I make mine from raw milk in a dehydrator and previously in an oven which I could go down as low as 110-115 degrees using my pilot light on. I know you said that your oven only goes down to 170, but maybe try using just your oven light to incubate the yogurt; if you have an oven therm, you could try it.
Before my dehydrator, I initially turned the oven on the lowest setting, including the light, watching the oven thermometer; then when it hit 110, I turned the oven off, but left the light on. I found that it stayed at between 110-115; being the temp. you want to incubate at. Other than the temp. I heat my milk to, since it’s raw, there’s no difference in prep. I would use 2 tbslp.-1/4 cup of plain yogurt (preferably a whole milk.organic like Brown Cow, Seven Stars, Nancy’s or Stonyfield Farms, you really don’t want the milk powders from the low-fat versions) per quart of milk. After, heating the milk up, to between 170 and 180, don’t let it boil, take it off and let it cool to 110. Then add your starter; you can even add in stevia, flavoring (like the flavored stevia liquid drops or vanilla, whatever), or a little honey at this time, if desired or wait till later so people can do theirs individually.
Then fill up into half-pint or pint size Ball jars, cover and place gently in the oven. The longer you incubate the more tart it is, but more probiotics are there. Anywhere from 6-10 hours. Some people do more, then place in the refridge, undisturbed for 8 hours. You could test at different times, taking one out at 6, one at 8, ect… and then after the cooling process, compare consistancies and then you’ll know what time is best for ya’ll’s tastes. Add in fruits and stuff at eating time. I like using the individual Ball jar servings.
I also have some other ideas. If your oven light alone won’t keep the temp. right, I’d try the crockpot next. On the ‘Warm’ and ‘Low’ selections, you could fill it up half-way with water one day and test the temp of your crockpot, then you’ll know and you won’t have to buy the Yogurt maker (but if you decide it works better for you then go for it and don’t feel guilty when you tried your best using other methods). Try it with the lid on for 8 hours and the lid off another time, maybe a towel on another day and see if you get the right temp. with any of these options, without having to do the turning on and off thing I’ve seen with so many crocpot yogurt recipes-they seem like a pain; I just like to make it and let it do it’s thing. If you find you can get the water to stay consistant at around 110 using one of these ways, then put in your jars of yogurt with water about 1/4-1/2 way up and try it. I think w/having a warm selection, you’ll have success.
Besides that, If you don’t use raw milk, use regular pastuerized, not the ultra-past. (it won’t work) organic whole milk would be best (again the powdered milk problem and more fat is better in the final product). Also, very importantly, I recommend not using any gelatin or powdered milk to thicken it up as many recipes call for it; they’re not necessary if you incubate long enough and treat the yogurt gently while moving till the whole process is complete. With the way Gelatin is processed (except for Bernard Jenson’s version), free glutamate is created, i.e. MSG; not good. As for the powdered milk products, the methods of commercial dehydration create oxidized cholesterol, which is harmful to the arteries, and the high temp. drying creates large quantities of nitrate compounds, which are potent carcinogens; one of the reasons to avoid most processed meats for example are the nitrates.
SO having said all this, I hope you find a method that works without having to purchase something; but if you do, you’ll at least know you tried other things first! Then once you get your yogurt method established, you can make whey and cream cheese! YUM!!! And start soaking things and making smoothies, popsicles and maybe yogurt leathers (haven’t done that one, just read about it). How exciting!!! I’m sorry I don’t have a recipe for you specific to a crockpot.
Let us know how it goes! Sorry I was so long-winded, too.
Rachel