Milk used to be in a glass bottle. At the farmer you could get fresh milk and it was put in a milk jug or milk cooker. The milk bottle had a blue aluminum cap and the buttermilk a red. The bottles for custard and yogurt also had their own color cap. Glass bottles had disadvantages: they were heavy, could break, and were difficult to clean for reuse. That's why today milk is in a cardboard pack or plastic packaging.

Glass bottles