Susan - you are correct in that this kit is probably just for emergency use and therefore not real a problem what container you use to heat water in. I have used a tin can billy many times and only recently discovered there was a plastic liner in them. I never cared until the Internet told me I should. Our local WalMart has some blue granite ware, can you expand on the "warm colours" concern?
Mike
Warm colors red, orange, yellow in glass, pottery, or granite
wear may indicate
heavy metals, especially in the old days.
USA manufactures became aware of this danger, and later, so
did foreign manufactures that export to the USA (& Canada).
So recent imports should be safe, no matter what color; but
I would still trust blue or white interior colors more.
The Walmart billies (old blue camping) were my favorite pot
in the kitchen. I could cook 3/4 lb beans in one and
then store it in the refrigerator, perfect. Their new camping
billy is only slightly fatter, much smaller than their stock
pot from the cooking-pans department.
Two warnings on granite wear 1) do not get them supper hot
or cool them super quick (cracking granite-glass) 2) do
not set granite wear container on a inclined surface that
is slick, because the container will slide off.
You can roughen the bottom by sanding or building up a hard
black finish or both.
You said:
I have used a tin can billy many times and only recently discovered there was a plastic liner in them. That is the problem. Some chemicals do not make you sick
right away, or in a way that you would connect to that
chemical. Heavy metals degrade kidney function but you
may not know it for decades. There are lots of sick
people waiting for a kidney transplant (i.e donor match).
Signing off
Hike4Fun (The other Susan)