If you want to see a similar process that is easier to understand, and also easier to do, you can brown your high carbon knives (not stainless) to a dull blue-black with vinegar, the process is called "browning" as opposed to blueing.
steel wool the knife so that the rust is mostly gone, and you have bare metal on the blade, you can also polish the blade if you like, it will be a smoother surface, dip the knife in either 60% or higher concentration alcohol and let it dry ( 100 proof vodka will work, but so will windex) This step gets all the oils and grease off the blade, make sure you don't touch the blade at this point or it will etch your fingerprints on it in rust, that is a bad thing (wear gloves if you are clumsy) Allow the blade to dry completely or hold it over a source of heat until the alcohol, vodka or windex dries (unnecessary if you are patient)
Using a smooth absorbent paper towel, soak the towel in vinegar (or 20% acetic acid if you can locate it) allow the excess liquid to run off and then closely wrap the towel around the blade, and then squeeze the towel to the blade surface so it touches all the contours. Then wrap a dry paper towel around it, and place the whole thing in a sealable plastic bag, get as much air out of the bag as you can, this creates an environment where rust forms in a lack of oxygen, so instead of the orange, fuzzy iron oxide rust, you get a smooth, hard, blackish rust that forms an oxidized layer on the steel.
WAIT three to six days to touch, move or open the bag, remove the paper, and you will see a hard black rust formed, lightly, with oiled steel wool (oooo) polish this layer until you get an even color, and then use it. What you will find is this layer does not rust easily, is not shiny or spotty and will last for a long time if kept reasonably cleaned and oiled.
This was a traditional metal finish long before blueing, and if you practice at it, you can also wrap thread or strips of the vinegar-soaked towels around it, and the edges will leave prints that looked like pattern steel or damascus.
I use this technique on knives I make for the kitchen and carrying, makes them look old and prevents rust well. Does take some practice, though.