My question was more if anyone knew what sort of a solution of
caustic the breweries used, that is to say, the caustic -to-water
ratio for a good clean without being unnecessarily strong. Having
once eaten holes in a SS container when I tried soaking it in
bleach, I don't want to overdo it!
To those who haven't used the stuff, caustics like lye are quite
awesome in their ability to vanish organic material, which makes
them ideal for this particular application, cleaning out an
unmodified keg through the tiny access hole.
Like all really strong cleaners, lye is powerful stuff, and care
must be taken (eye protection, gloves especially) when using it. I
usually take my clothes off immediately after working with the
stuff, and throw them all in the washer, since (as with acid) a
drop or two left on can eventually burn a hole in them. BTW the
slippery feeling you get on your hands when you expose them to
a lye solution is apparently the outer skin cells turning to mush!