Removing paint without removing japanning?

[Michael Titus]

I recently picked up a nice little combination square for a couple dollars at a yard sale. It's perfectly usable as-is, but the previous owner (or perhaps one of his children) painted over the black japanning with off-white paint. Is there a way to remove the paint while preserving the original japanning (and spirit vial)? Thanks!

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http://www.sawmillcreek.org/images/misc/pencil.png

[Rich Engelhardt]

Michael - I can't guarantee that this won't damage the japanning and/or spirit level - but - it's the least destructive method I know of.

Pour some white vinegar into a container large enough to submerge the pieces in.
Place that container into a large container with water in it - ie: setup a double boiler.

Heat the vinegar to ~ 150 degrees - or to the point that it hurts to stick your finger in it.
Put one of the pieces in and remove the heat. Let it "cook" until the vinegar has cooled down to the point you can stick your finger in it and it doesn't hurt.
That should take between 15 and 30 min, depending on the room temperature.

Repeat the above process a half dozen time - or less if you see the white enamel start to wrinkle.

W/luck, the adhesion between the white enamel and the japanning won't be all that great. You're really counting on a lack of surface prep to work for you here.

If/when you see the white start to wrinkle, take the piece out while it's still hot, try rubbing the white enamel off.
I use those cheap leather work gloves HF has for this step. They protect your hands from the hot metal & the leather acts as a mild abrasive.

A final rinse under hot, hot, hot tap water - then set the pieces on a towel to dry.
The heat should make them dry quick enough that any possiblity of rust isn't a concern.
Using a hair dryer to speed the process is an option also.

In all honesty - I've had less than 50/50 luck using this method to remove paint (usually some sort of enamel) from old lacquered door knobs and hinges, while keeping the original factory lacquer on them as intact as I could.
Most of the time, what's underneath is pretty beat up - which is probably why they were painted to begin with.