Failing at yogurt

[JosefR]

First batch, water bath to 195, cool down to 110. I made a half gallon in quart jars with a tub of yogurt from the store and my dehydrator set on yogurt for 12 hours. Turns out, "yogurt" is about 135 degrees. Turned out perfect. I saved a bunch of ice cubes of the yogurt.

Next batch, 1 ice cube per quart jar. 12 hours and fail. Realized "yogurt" was 135 and lowered it to a 110 setting. Added another cube to each and 12 more hours. Success.

Next batch, I used a powder starter in a quart. Success.

Drained and used the whey for the next batch, 12 hours, fail. I added another 1/2 cup whey per quart and 4 more hours. Fail.
Boiled that for 10 minutes to see if it made ricotta, waiting to cool.

So there seems to be no rhyme or reason for the fails. Or the successes. Looks like I can count on a commercial product, but not on mine for starter.

EDIT: The quart of boiled sour milk resulted in 1/4 cup of watery super sour yogurt and one piece of ricotta I felt as I was slurping it. Now I still have a quart of super sour milk in the fridge. Is it buttermilk??

[mohair3]

I use a yogurt maker and powdered starter, but it's been a while since I made yogurt, so can't remember if I ever made any with the previous batch.

What do you mean you are saving "ice cubes"?

[JosefR]

"I saved a bunch of ice cubes of the yogurt."
I poured yogurt in ice cube trays and froze them.