How can you see the protein in milk?

The students took regular milk, heated up in a beaker, then added vinegar, stirred rigorously. A reaction began to take place with the protein separating in clumps from the water in the milk until it became two parts: protein and water. When it became clumpy they drained out the water once the protein separated from the milk. Once all the water was drained out the students used paper towels to dry off the remaining protein and formed it into a figure or shape of some sort. Over the next 24 to 48 hours that shape will dry and become hard as a rock and then the students can paint it. This lab is designed to show the chemical process and the chemical make up of milk; that once you pull all the water out and all that's left is the protein it dries into a hardened form.