I was reading some web pages about how to make milk solids and I almost fall off my rocking chair. There were people suggesting making milk solids out of butter, out of sour milk, using all sorts of abnormal things to make it solid, and all sorts of weird ideas.
Milk solids are very easy to make. First of all milk solids are the protein which is in milk, they are not the fats.
Take a glass of milk and heat it up in the microwave for two minutes.
Add four tablespoons of vinegar, and stir it until it starts to clump.
Scoop the clumps out. Those are milk solids.
You don't make milk solids out of butter!
IF you just happen to be trying to make clarified butter, THAN you can get some small amount of milk solids out of that process -- yes, but you don't make them from the butter that would be mondo expensive!!
Powdered milk comes in a few varieties, if you buy the non-fat powdered milk and add just enough water to some to make it into a kind of paste, then you have made milk solids as well. The whole milk powdered milk will not make milk solids! You must use the non-fat variety.