Friday, March 1, 2013

Cleaning an Oil Stone

With so many woodworkers today using Japanese water stones, slow speed grinders, and advanced sharpening systems made by brands like Tormek and Work Sharp, the classic oil stone seems to have fallen by the wayside in popularity.  I personally like the oil stone method for two reasons, limited expense and low maintenance.  In many cases I do desire additional honing of chisels or hand plane irons, but will just use fine grit sandpaper with water or mineral spirits for lubrication.

Recently I wandered across an oil stone at least 60 years old whose surface was pretty heavily clogged.  It looked to be a nice stone and chose to revive it instead of tossing it.  I knew there were two main things I needed to expel from the stone: oil and built up minute bits of metal.

Finding a Proper Solvent

To remove the honing oil from the stone, I was going to need something fairly volatile with a low viscosity.  Not only should this solvent cut the oil from the stone, it would also most likely serve as a lubricant to expunge the tiny bits of metal.  It would also have to be fairly inexpensive, since I would need a good amount to soak the stone in.  After a little online research, I decided to try using charcoal lighter fluid.

Items Needed for This Task

Old Oil Stone
Cheap Plastic Shoebox with a Lid
Charcoal Lighter Fluid
Small Wire Brush
Scrap Wire
Safety Gear (goggles, gloves, respirator)

The Setup

Coil up the wire, pull it apart, and flatten it as much as you can, like in the picture.  The wire will be placed under the stone to slightly lift it and allow more surface contact between the lighter fluid and your stone. Place the wire in the container and the stone on top of it.  Pour the lighter fluid into the container and submerge the stone to at least the halfway point.  Put the lid on the container and leave it alone for at least a couple of hours.  It may take a while to work the oil out of stone, especially if it is an old stone.  I left mine overnight in the detached garage.

*** Do not attempt this project near any sparks, flames, pilot lights, or people smoking. ***

(They call it lighter fluid for a reason.)

Much, Much Later

After some time has passed, come back and check on your stone.  Look in the lighter fluid for blobs of oil.  I found some at the bottom of mine, even though the stone had sat untouched for decades.  You might also find some very fine black or dark gray bits of metal in the fluid.

At this point, you may want to wear rubber chemical gloves, the lighter fluid can dry your hands out pretty bad.  I also might suggest doing the next step wearing goggles and in a well-ventilated area.  You may also choose to wear a respirator, the fumes can be pretty nasty.

My stone was still caked pretty good, so I decided to hit it with a small wire brush.  These are great tools for restoration and can be found with the welding supplies at your local big box store.  Working it with the wire brush helped the gunk was slowly come out.  I found the best method was briskly rubbing in a circular motion,dipping the brush in the lighter fluid to wash it out and keep the stone lubricated.  The wetter you keep the stone, the easier and faster this process will be.


After a few overnight soakings coupled with scrubbing, my stone ended up 95% cleaner.  I will say there are a few select areas I was having trouble completely cleaning.  I think this process maybe good for regular oil stone cleaning, but is probably not the best for reviving a age old stone to its former glory.

I may consider coming back and soaking again, using a wire cup brush on my angle grinder if necessary.  Then again, I may search online for another method just to try something different.  If you have any other ideas, please leave them in the comments section - I would love to hear from you.