Are you meaning such as butter milk..?? That is what my grandma calls clabbered milk .(we're from alabama it's more common out there).  If this is what you are talking about? I make it all the time ,I use about 1 half lemon squeezed into about a cup of milk then wait about 15 minutes. You need to wait about 5 minutes or so to see if you have added enough.It thickens up really quickly. Or if you don't have any lemon in the house I use about a couple tsps. of vinegar. I think lemon taste better then vinegar  but for recipes I can't taste any difference. But it does work.