I used organic pasteurized homogenized milk. Do not use ultra-pasteurized milk. Fresh ricotta should keep up to 2 weeks in the refrigerator, or it may be frozen. This yields about 1 1/2 pounds of ricotta, depending on the milk you use.
Pour milk into large pot. Heat on medium until temperature reaches 190-195 degrees fahrenheit, stirring often to avoid scorching at bottom of pot.
Gradually pour vinegar into hot milk, stirring gently until all vinegar is stirred in. Cover and let sit for 5 minutes until curds and whey separate.
Place a single layer of butter muslin in colander. Use slotted skimmer to transfer curds to muslin lined colander. Let curds drain for 5 minutes or longer, depending on how firm you like your ricotta cheese. Season with a little salt and toss to distribute salt.