Esteemed Galoots,

There are indeed two types of Dykem blue products. One is a machinists
layout dye. This product contains a volatile solvent that dries super
fast. The point of this stuff is to coat a piece of metal stock so that
it can be marked with layout lines prior to machining/working/forming.
Works really well for that purpose too, since when you use it with steel
or aluminum you end up with bright, shiny layout lines on a dark blue
background.

The second Dykem product is called hi-spot blue. It does not dry, at
least not very fast. This is the stuff that you want to use in
conjunction with a reference surface to show the high spots on your
plane soles. Having used this product, I can't distinguish *any*
difference between it and prussian blue oil paint. I bought a small tube
of prussian blue and thinned it with a little raw linseed oil to achieve
a nice thin blueing agent. A tip that was given to me and that I'll pass
on is that you can never use too little of this stuff. Try putting down
a thin layer of blue on your granite surface plate and then wiping it
off with a clean rag. See how the granite is still blue, even though you
just wiped it off? That's just the ticket for flattening a plane sole.
When you're done and want to clean up your granite use a solvent like
alcohol to get rid of most of the blue. Have fun and good luck.

-Andy
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