Glazed stone

[Eben Fourie]

Can someone please explain what a "glazed" stone looks / feels like ? Especially water stones. If anyone has a photo that would be great.

How do you prevent stones from becoming glazed ?

How do you fix/restore a glazed stone ?

Thanks in advance,
Eben

[Zach Dillinger]

Waterstones shouldn't become glazed unless you are using them without water. The stones wear away very quickly when used properly and when they are flattened. This will prevent glazing from happening.

Oil stones are another matter. They can become glazed if the lubricant you are using is too thin to lift the metal slurry off the stone. There is a fine balance point when finding an oil for stones. The thinner it is, the faster the stone will cut but it is more likely that it will clog up. Thicker oil prevents clogging but means your stone will cut even slower. If you suspect your stones are glazed, wash them in kerosene, let them dry, then flatten them. This will take care of the problem.

EDIT: Check out http://norsewoodsmith.com/content/cleaning-old-oil-stone for more tips on cleaning up nasty old stones.

Take care,

Zach

[Scott Burright]

It's easiest to notice a glazed or clogged stone by feel. It doesn't cut anymore. There's very little friction as you drag the edge along. You can feel it not cutting.

I use oilstones. If a stone feels a bit clogged, you can put a good puddle of oil on it and sort of squeegee it off with your finger or a rag. If that doesn't get it, I go to dish soap and a stiff nylon brush. Sometimes scouring powder. Of course, lapping fixes anything.

For a few years, I was using my oilstones totally dry and just knocking off the swarf with a nylon brush or a rag. The only time any of them seriously clogged, it was my coarsest silicon carbide stone, at the end of a marathon regrinding (by hand) of a set of 6 turning tools whose bevels had been murdered by a bench grinder. That gives you some idea of what it takes to really clog a stone.

I've gone back to using oil again after that experience. Just seems to keep the swarf out of the way better.