Like many of you, I spend Saturday morning
thinking about obscure kitchen tools that
I don't already have. Like these two:

http://cgi.ebay.com/ws/eBayISAPI.dll...m=220201592569

Anyone have a clue as to how they work?
Are they missing any pieces? Why would
anybody boil milk?

So, to educate myself, I looked around
for other examples, but that only added
to the mystery:

http://cgi.ebay.com/ws/eBayISAPI.dll...m=150220314469

http://cgi.ebay.com/ws/eBayISAPI.dll...m=150218292500

Whoa! A completely different design!
At least, one of them has instructions.
Apparently, these sit in the bottom of
a pot of milk, spiral side down. Steam
bubbles presumably travel along the
spiral groove before exiting through the
hole. What's the purpose of doing that?

The instructions say it prevents boiling
over, but wouldn't the real problem in
boiling milk be scalding? Is preventing
boiling over the only purpose accomplished
by this tool?

The name of the latter unit, "Milk Saver",
implies that this is done to preserve milk,
maybe an early form of pasteurization?