durable plane iron marking method is handy for bevel-up planes

I have a small collection of plane irons that swap between three bevel up planes, as needed. I really like this approach because it makes it easy to get the right cutting angle in any situation. But this also means keeping track of which iron gets sharpened at which angle. I was using a so-called permanent marker in this capacity for a while, but they aren't what I would call permanent on a shiny steel surface that comes in contact with oil and water regularly.

Marked plane blade with wooden stylus. The large number has just been done with bluing fluid. The small, half-faded number is from a "permanent" marker.

So, I landed on the idea of using bluing fluid. The procedure is pretty simple, but there are a couple of easy ways to screw it up that I have learned how to avoid. Here's the procedure:

Marking my box full of blades takes only a few minutes.

1. Get some liquid bluing fluid.
2. Clean the plane blade thoroughly in the area you want to mark. You can polish up with an abrasive if you want to be sure it's clean.
3. Make a stylus by sharpening a stick of wood. Cut off the very tip so it has a little width, matching the line you want to make.
4. Write with the stylus. You'll need to dip it in the bluing fluid often. Avoid the temptation to soak the whole stick. I understand it's nasty stuff and not something i would choose to get on my skin, plus you don't want o make a puddle where you are trying to write. The fluid goes on clear, and turns the surface nearly black in about 3 seconds. Be patient and careful, because this won't erase without an abrasive.
5. Clean the fluid by dousing in water. You don't want to wipe off the bluing fluid with a rag, because you'll most likely end up with a smudge instead of numerals. I like to take it over my sink, start the water on high, and then put the blade under the tap in one fluid motion. That way the fluid is long gone before it has a chance to discolor the surrounding area.
6. Prevent rust by thoroughly drying the blade and applying oil or another rust preventative as you normally would.

My box of blades would be excessive for one plane, but it serves these 3 nicely. I often pop a high-angle blade in the jointer to avoid tearout and save the smoother some work. The jack plane is my primary shooting plane, so it often holds something with a low angle.