Indeed milk paint seems to be a 19th century thing, originating in France during the French Revolution when oil was scarce. Have you read this document?
http://www.historicnewengland.org/preservation/your-older-or-historic-home/articles/pdf153.pdf. It is very interesting, it also has some paint recipes. Funny to see that they added oil to the milkpaint, which now often is just milk, lime and pigment.
Another interesting bit of information is here:
http://www.milkpaint.com/about_history.html. They state that they reintroduced milk paint in 1974 to make a paint that was ecologic and because it is a good reproduction of the faded and weathered look of antigue painted furniture, even if that furniture had been painted with oilpaint originally.
Another interesting paint recipe used before the 19th century was "glue paint". Pigments dissolved in hide glue. The quality of this paint was very low, it easilly rubbed of.
So, to put paints on a (rough) timelime. Milkpaint was know allready in antiquity. Then in the late middle ages oil paint replaced much of the milk paint uses. Probably for cheap stuff they also used glue paint at that time. Early 19th century, milkpaint has a comeback as a wood finish. Then with the invention of the paintcan in 1868, paint didn't need to be prepared on the job anymore, you could buy a tin of paint in the shop. This was always an oilpaint, with increasingly complex chemical structures. Then finally in the hippy age, milkpaint comes back again.
Always fun to delve around a bit in the history of things.