What is the best kind of pot (material-wise) to heat milk for home made yogurt?

After seeing the comments below, I'm a bit concerned. Over the years, I've made yogurt in an aluminum soup pot and never had any problems-no grey look or bad taste. After heating the milk and adding the yogurt, I just put the covered pot in the oven until it solidifies. It's delicious, but I'll try it with my stainless steel pot next time.

Stainless steel. Milk contains lactic acid. Anything acidic will react badly with aluminum or unlined copper, for example. The milk (or anything else acidic such as lemon curd) can actually turn grey, take on a metallic taste, and even create toxic compounds. Non-stick is probably okay, but once the non-stick lining begins to deteriorate, it's time to toss it. The material is quite toxic. Do you have a Ross or TJ Maxx store nearby? They're great sources for affordable stainless pots.

I used to make it in a quart jar (glass) over the pilot light on a gas stove. Can you tell it's been a while? I would go with stainless steel. Nothing reactive.

Recently I’ve been using a clay olla from Columbia - A Chambra pot. I heat the milk in the pot on a low low flame till the milk "shimmers", let it cool to body temperature, add my yogurt starter, cover, and place in an oven that has been prewarmed to 115*F and turned off, let it sit overnight, and refrigerate 12 hours before eating. The clay pot lends a distinct earthy flavor I like, and the clay absorbs some moisture, so the yogurt is a little bit thinker/firmer. I don’t repackage the yogurt as it will break and become too thin as a result, I just serve as I go from the pot. An added bonus is that this method continually treats the clay pot to a milk casein treatment, which helps its longevity. As for cleanup – I soak the emptied pot in warm water and scrub with a Japanese reed whisk/scrubber. NO soap! I use this pot for lots of other things too, so on a side note I want to make a huge shout out for traditional Clay Pot cooking.

I just used a normal nonstick pot. It was easier to clean and the yogurt came out just fine.

I use two pots, one inside the other. Outside pot for water @above the temp you want the milk to be,inside pot for milk. Outside pot should ideally be filled to the milk level, but will work if it's shorter. Use a trivia or towel to keep the inside pot off the bottom. I pasturize my milk (140F for 30 min.) then cool the milk in a sink full of cold water. Put it backin the now cooled water bath and inoculate. Summers I keep it warm on the sidewalk. Winters I use either the oven with the light on or a heating pad.

Stephanie, thank you so much!
Do you find that the stainless and cast iron are easy to clean as well?

I have used many pots over the years. My go to currently is a stainless (not fancy) stock pot. I have dreams of finding a beautiful and large double boiler but that will have to wait for a bigger kitchen.. Dutch oven worked well also but so heavy to pour out..