I'm trying to make yogurt, but it won't turn out. Can someone help?

Don't get frustrated. There really aren't that many variables to keep track of.

1- I don't know the age of store bought yogurt but I have never had just-purchased yogurt not work as a starter. I have had month old yogurt from my fridge not turn out. If you don't plan on making yogurt often enough to keep you starter viable then consider freezing some in ice cube trays.

Whatever starter you use- make sure it lists "live, active cultures". Personally I wouldn't use a flavored yogurt as a starter.

2- I don't think that is enough starter. I will use 1/4 cup of starter for a quart of milk. If you are using 1 cup of milk that would be one Tbs of starter (12X the amount you used).

3- It depends. The goal is to denature the albumin proteins in the milk. 180F is hot enough if the milk is held at that temperature for at least half an hour. It needs to be held at 190F for closer to 10 minutes.

4- You need to get better control of your temperature. 130F will kill your starter but erratic temperature fluctuations will also produce very poor yogurt. Without a temperature controller or manual intervention your slow cooker will get much too hot- even with a water bath.

More successful approaches are to put it in a draft free place in an insulated container, or in your switched off oven.

5- The humidity is not going to play a role unless it is condensing into your container enough to dilute things.

Good luck. I hope you get it working. Fermenting milk is fun.

I see that you have had success with the answer above, so congrats. I have been using these general guidelines for making yogourt and it's turned out nicely except for once (and only because I needed the oven half way through making the yogourt - poor planning on my part!):

• 2L of 3.8% organic milk (full-fat happens to be my preference because I prefer the taste)
• I initially used plain organic Greek yogourt as a starter, 4 tbsp. for the 2L of milk
• Heat milk to 180F and hold at that temp for 30 mins.
• Cool down to 110F (I use a quick cool function in my fridge)
• Add the starter and mix gently (I use a silicone spatula - I read several recipes that emphasize the 'gently' part; I think it has to do with not breaking apart the molecules)
• Place in oven with light on and leave for 8-10 hours or until desired acidity is reached.

I use a dutch oven to make the yogourt and I always use a thermometer. I keep a small mason jar of the yogourt as a starter for next time and have occasionally kept it for two weeks between batches with no ill effects.

I then strain the yogourt in a cheesecloth-lined mesh colander in the fridge for 4-6 hours or until I have my preferred consistency of thick Greek-style yogourt. The final yield is about a litre and costs about half of what I would pay for organic Greek yogourt in my part of the world - and the taste is far superior in my opinion.

Maybe if your oven looks like it won't go that low, try to see if it will stay on if you move the knob below the temperature markings. I found although mine said it could only go to 60 degrees Celsius (140 F) it actually will go lower and maintain the right temp to make the yoghurt. Just a thought :-)

If you find following a detailed recipe too error-prone, start simpler instead. Make your earliest efforts as simple as possible, and start small. Your first successes can come by following this simplified recipe:

(1) Warm the milk to 110 degrees Fahrenheit.

(2) Add yogurt.

(3) Keep the mixture in a warm but not hot place for 6-8 hours.

Yogurt should grow as long as it has food (lactose) and is warm and is not being out-competed by another microbe colony. Cultures can die, and simply trying again with fresh yogurt or working on keeping the temperature in a more comfortable range for the cultures can lead to an earlier success. Some steps may be extraneous for your first experiments, but add them back in after you start to see some moderate success (as another writer pointed out, pre-heating the milk helps the yogurt thicken more). Probably the most difficult part is maintaining the temperature within the cultures' optimal growth range; 100-120 is typically OK, but colder leads to slow/no growth and hotter can kill the cultures, making a fresh cheese instead of a yogurt. Most cooking appliances are not designed to operate within this temperature range and that is the chief difficulty--ovens and crockpots usually don't go below about 140 or 170 F--so many people will put it in a turned-off oven with residual heat, and with the oven light on or with tins full of hot water next to it (120-140F) to keep it warm. A friend of mine would pour some milk on top of the last spoonful in her yogurt cup and leave it next to the warm fan vent of a computer. She'd come back in the morning and she'd have another cup of yogurt waiting for her.

I used the recipe on this website for my first time making yogurt. It turned out perfectly.

http://m.chickensintheroad.com/cooking/homemade-yogurt-in-a-crock-pot-and-yogurt-cheese/

I used a 5.1 oz. Greek yogurt to 1/2 gal. of milk.

After stirring in the live culture yogurt, I let it set for 11 hours overnight in the oven with the light on (Crockpot wrapped in a large beach towel). Stirred it again in the morning. My cousin leaves hers setting out longer covered with cheesecloth which results in a thicker yogurt.

I made a second batch today using 1 cup of the first batch of yogurt. We'll see how that turns out in the morning.