I have run my own stone and marble workshop for over twenty five years and it became a regular occurrence to have visitors looking to buy a piece of stone or marble to try out stone carving. I have a soft spot for all wannabee artists so I would never charge for the stone, asking instead that they bring back their piece of work so that I could see how they got on.
In all those years no-one ever came back!
Now I know that most people are really decent and would have come back to show me their efforts, so I have put this lack of response down to the fact that most of these novice carvers simply chose the wrong type of materials to start with and therefore never actually managed to finish the piece of work.
Most of the hopefuls I saw over the years wanted to carve marble and so, in spite of my advice to try a softer stone, they trolled off happily with a nice piece of white Carrara or Italian Botticino Fiorito never to be seen again. (by me anyway!)
The simple fact is that stone and especially marble carving is hard work. Unless you choose a soft and relatively easy to work type of stone to start with and you select the right tools, you will easily become discouraged and give up long before you are able to develop the practical skills necessary to work the harder stones and marble.
To help would be stone carvers choose the right type of stone, I have tried to create a kind of Mohs Scale of hardness of the kinds of stone that you are likely to find in your local stone yards.
This is not a scientific scale, it is based not only on hardness but also on the practical workability of the stone. I have assumed that you will be working with hand tools not power tools.
The scale is numbered 1-10. 1 being the softest stone and 10 being the hardest.
1: Cotswold Stone.
Tools: Hardened steel chisels with wooden handles similar to wood chisels used with a Wooden mallet. Steel chisels with steel bulb end, for use with lead mallet or "dummy". Can be sawn with a hand saw just like a timber saw.
Advantages: Very soft to work. all types of chisel will work. Can be cut to size with a hand saw, excellent for practising hammer and chisel technique.
Disadvantages: : Finished carvings will have poorly defined detail, the stone is too coarse to give a sharp finish. Risk of exposing hard shell in the course of work this may spoil the look of the finished job. Too weak to easily make thin panel carvings for example house signs or decorative plaques.
Conclusion: : May be the right material for larger sculptural pieces.
2: Bath Stone.
Tools: Hardened steel chisels with wooden handles similar to wood chisels. Wooden mallet. Steel chisels with steel bulb end, for use with lead mallet or "dummy".
Can be sawn with a hand saw just like a timber saw.
Advantages: : Soft to work. all types of chisel will work. Can be cut to size with a hand saw, excellent for practising hammer and chisel technique.
Disadvantages: : Risk of exposing hard shell in the course of work this may spoil the look of the finished job. Too weak to easily make thin panel carvings for example house signs or decorative plaques.
Conclusion: : Finer grain than Cotswold etc. Better definition of carving. Good choice for first project.
3: Portland Stone.
Tools: Hardened Steel chisels with steel bulb end, used with wooden masons mallet. Fine tungsten carvers chisels used with small steel club hammer.
Advantages: : Memorial grade is a very high quality stone, fine grained good definition of detail. Strong enough to make thin panel carvings for example house signs or number plaques.
Disadvantages: : Availability of finer grade material. Some risk of exposing hard shell in the course of work this may spoil the look of the finished job.
Conclusion: : Finer grain than Cotswold or Bath stone etc. Better definition of carving. Good choice for first project but harder to work than bath stone.
4: Portuguese limestone.
Tools: Hardened Steel chisels used with steel hammer. Fine tungsten carvers chisels used with small steel club hammer.
Advantages: : High quality stone, fine grained very good definition of detail. Strong enough to make thin panel carvings, for example house signs or number plaques.
Readily available from fireplace manufacturers .
Disadvantages: : Not often available in sizes thicker than 30mm.
Conclusion: : Finer grain than any of the previous stones. Better definition for carving. Good choice for first project but harder to work than bath stone.
5: Italian Black Slate.
Tools: Fine steel chisels, tungsten carvers chisels used with small steel club hammer.
Advantages: : Very fine grained very good definition of detail. Strong enough to make thin panel carvings, for example house signs or number plaques.
Disadvantages: : Hard to work, will chip easily while carving. Not for exterior use.
Conclusion: : Good start if you want to carve slate.
6: York Stone.
Tools: Tungsten chisels only, tungsten carvers chisels used with small steel club hammer.
Advantages: : High quality stone, fine grained very good definition of detail. Strong enough to make thin panel carvings, for example house signs or number plaques. Readily available from garden centres.
Disadvantages: : Very hard to work. steel tools will blunt very quickly, Dust is hazardous so wear a mask!
Conclusion: : Not a good choice for novice carvers.
7: Welsh Grey Slate.
Tools: Fine steel chisels, tungsten carvers chisels used with small steel club hammer.
Advantages: : Very fine grained excellent definition of detail. Strong enough to make thin panel carvings, for example house signs or number plaques. Very strong. Readily available. Ideal for exterior use.
Disadvantages: : Hard to work, will chip easily while carving.
Conclusion: : Super quality slate but not for novices.
8: Westmoreland or Cumberland Green Slate.
Tools: Tungsten chisels, tungsten carvers chisels used with small steel club hammer.
Advantages: : Very fine grained excellent definition of detail. Strong enough to make thin panel carvings, for example house signs or number plaques. Very strong.
Disadvantages: : Very hard to work, tends to chip easily while carving. Ideal for exterior use.
Conclusion: : Super quality slate but not for novices.
9: Marble.
Tools: Tungsten chisels only, tungsten carvers chisels used with small steel club hammer.
Advantages: Very fine grained excellent definition of detail. Strong enough to make thin panel carvings, for example house signs or number plaques.
Disadvantages: : Very hard to work.
Conclusion: : Try softer materials first, if you must try marble look for a paper white marble from Turkey, take the advice of your local mason!
10: Granite.
Tools: Nuclear powered laser cutters only!
Advantages: :Super Hard.
Disadvantages: : Ridiculously hard to work by hand.
Conclusion: :Try bashing your own kneecaps with a hammer, it will hurt less!
That concludes "Walkers Scale of Hardness". I have almost certainly forgotten some stones and as the scale is based on my experiences over the years other people may have differing opinions. If you are a stonemason or carver and have a different view, or you have a local stone you think should be included on the list please contact me and I will consider editing or adding to this article accordingly.
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