Thread: Opinion wanted on these stones

Today I possibly got an amazing gift from my mother.

She is a master book restorer, and one of her friends died a couple of weeks ago and his wife wanted to get rid of all his tools and stuff. So when my mother helped her clear out the garage, the widow asked her 'oh by the way, there are a couple of stones lying in the basement, is there anything you can do with them?'

These stones are very old (at least 30 or 40 years but probably older) and were originally used for lithograph printing. They were sold as rubbish when the lithography business went downhill. They were bought and sold a few times among my mother's colleagues.

Their use of the stones was twofold: to sharpen tools that should be very sharp, and to use them for thinning leather: a very useful property of those stones is that they will not dull a knife when it touches the stone after leaving the leather.

The stones are milky white, but most of the surface is currently covered in sand and grime Only a small strip on the side of stone in the left picture is reasonably clean. when I rub my hands over the white patches, it feels like the belgian coticule, but softer.
The stone in the right picture still has stone lithograph negatives printed on it. These negatives were sanded off for each new printing design.

Perhaps one of the most amazing facts: these stones are 25 cm by 20 cm. one is 8 cm thick, the other 4 cm thick.
My mother thinks that these stones originally came from france and that they were hideously expensive.

I'll try to clean them up sometime this week, though lapping will not be easy. they are almost as big as my sandpaper itself :-)

Pictures are attached. What do you think?

I have no idea - but this is very interesting.

Can't you have the grit checked?

What can I say, take a cheapie but quality blade, loupe / microscope - do a few passes - take a look at the marks, if you're brave - test-shave a small area. Repeat as necessary until you feel comfortable in your understanding if the stones are good for razors or not

Good luck
Ivo

Originally Posted by izlat

I have no idea - but this is very interesting.

Can't you have the grit checked?

What can I say, take a cheapie but quality blade, loupe / microscope - do a few passes - take a look at the marks, if you're brave - test-shave a small area. Repeat as necessary until you feel comfortable in your understanding if the stones are good for razors or not

Good luck
Ivo

Thanks.

A flooded basement and problems with central heating have distracted me somewhat, but I am still trying to figure out how to lap these things.
They need it, if only to remove 15 years of accumulated dust and dirt.
Underneath that they are as white as milk.

I don't want to cut them up just yet, but how would you lap a stone that weighs about 8 kg and is almost as large as your average sheet of sandpaper?

Originally Posted by Bruno

I don't want to cut them up just yet, but how would you lap a stone that weighs about 8 kg and is almost as large as your average sheet of sandpaper?

How about the easiest: lapping each other (I know it's pretty obvious but should work?)

Cheers
Ivo

Find a flat area and try to hone a knife first to see how it cuts and what finish it leaves to the edge.

PuFF

If you look at this page of wikipedia:

http://en.wikipedia.org/wiki/Lithogr..._early_process

It says that early lithography used limestone.

Here too you get pretty much an idea as to how it works and what sort of stones lithography uses:

http://www.howstuffworks.com/stone-lithography2.htm

Originally Posted by PuFFaH

Find a flat area and try to hone a knife first to see how it cuts and what finish it leaves to the edge.

PuFF

I hadn't thought of that. Good call.
If the finish on say a kitchen knife is not excellent, I know I don't have to try using it for razors.

Originally Posted by Kees

If you look at this page of wikipedia:

http://en.wikipedia.org/wiki/Lithogr..._early_process

It says that early lithography used limestone.

Here too you get pretty much an idea as to how it works and what sort of stones lithography uses:

http://www.howstuffworks.com/stone-lithography2.htm

Thanks for the links.

If those are indeed limestone, I suspect they are not overly expensive (couple of 100s for a new stone similar to mine.)

If the knife test turns out Ok I might have them cut into norton sized blocks for convenience.