slate as a sharpening stone

[Trafalgar]

A lot of people use strops with pastes which then in effect levels all the differences between hones.

Very true.

 

[MIGNAL]

Well I guess it can be said that stropping and paste is fantastically cheap compared to a 10,000G stone. I bought a bar of the Green stuff 10 years ago and I doubt that I've gone through 1/50 th of it!

 

[bridger]

once long ago I had a slate/sandstone two sided stone from china. it was too slow to be useful to me.

a couple of years ago I bought some slate tiles at the local builder's supply and cut them up to hone sizes and flattened them. they were spectacularly unsatisfactory as sharpening stones. so soft that the surface quickly became rutted, so slow cutting that I'd die of boredom before getting to an edge and the effective grit was much lower than the look or feel of the stone would indicate (it scratched the heck out of the tool).

 

[Cheshirechappie]

once long ago I had a slate/sandstone two sided stone from china. it was too slow to be useful to me.

a couple of years ago I bought some slate tiles at the local builder's supply and cut them up to hone sizes and flattened them. they were spectacularly unsatisfactory as sharpening stones. so soft that the surface quickly became rutted, so slow cutting that I'd die of boredom before getting to an edge and the effective grit was much lower than the look or feel of the stone would indicate (it scratched the heck out of the tool).

As Bugbear pointed out earlier in the thread, 'slate' is a word that covers a great variety of rocks. North Wales, for example, has many slate deposits - there's barely a hillside that hasn't been scratched at for slate at some time or another, and some of them very extensively - but there are very few deposits that make decent honing stones. To take any old roofing slate or slate slab and assume it will match the commercial hones is very likely to give unsatisfactory results. Might still make a very passable roof, though.

 

[bridger]

the stuff was cheap enough to give it a try.

no idea where the material was quarried.

 

[adrspach]

My guess if ti was new at that time Brasil, Portugal or China were main imports here.

 

[sdjp]

The slate doesn't really cut much at all, but it does seem to burnish or polish edges very well.

Indeed - I have a similar welsh Dragons Tounge, and it's perfect for the straight razor - not least because it polishes well, without cutting too much. I've yet to take the chisels to it, but great on knives after a 3000 grit ceramic. And huge - 9x3 inches … no need to faff to get the blade covered.

Just in passing, I'm not sure that the 'proper' slate hones are technically slate at all - mine has no discernable cleavage planes. I gather they are made from a material properly called 'hornfels' which is often found in the same areas as slate beds, but is geologically slightly different. In slate, the mineral grains are aligned by pressure to give the characteristic easy cleaving into thin sheets, whereas in hornfels the mineral grains are not so aligned.

Ah, that makes sense!

Both slate and hornfels are metamorphic rocks - converted from others by heat and pressure. Hornfels tend to be heated more in the transformation, which fuses the layers, and leads to a typically cubic fracture plane; whereas the slates are under more pressure, hence the differing transformation. Also, slate can be transformed into hornfels, by subsequent processes, but I'm not aware of any cases of hornfels -> slate transformations.