Gyelt Tuinstra - Sculpting Stone, some practical tips

This is a compilation of answers I gave over the years, e.g. on a stone sculpture maillist. Please feel free to write me with corrections, additional info etc. that I may publish here. (Gyelt Tuinstra (email: beelden@ergoarte.ch) This is in no way a complete howto but perhaps it will grow over the years.

  1. I need to learn what it takes to carve something thin and free, like a curved arm, or a finger. Also undercuts like in textile folds, without breaking them.
    I work mainly in marble, which is I think more brittle than sandstone or limestone. (more...)
  2. I'm presently working on a dry stack wall. It's challenging and fun to shape the stones to fit each other. I think my tools are more than sufficient but I'm having pain in mainly my striking forearm and elbow. I have a 2, 3, and 4lb hammer. (more...)
  3. I'm sure the angle of the strike varies considerably by what you are trying to accomplish but are there any guidelines you could give me that might help me be more efficient? (more...)
  4. Dust, ist it really dangerous? (more...)
  5. Could you supply the name of the place where you get the stone tested for asbestos (more...)
  6. What (not) to look for in angle grinders (more...)
  7. Some experiences with safety (not a full list! use your own brain please! (more...)
  8. How I move stones up to 2000kg (more...)
  9. Dust cannot be that dangerous, can it ? Only anecdotal. I've known dozens of carvers and cutters who were older than 70, some of whom were still actively working (more...)
  10. Need for gloves: Maybe it's just me but I sometimes miss the chisel, and as a result I have a bone spur on my index finger knuckle which I've cracked with my hammer many a time. Does anyone know if there are special "armoured" gloves on the market that I could buy, to help soften the blows? (more...)
  11. I have to polish flat and curved pieces, I guess one of the most difficult things is knowing how much pressure to use. But I guess that comes with practice, also how much water, a stream or a trickle. (more...)
  12. I do go up all the grits slowly, but with the wet surface i find it difficult to see if I have done enough! (more...)
  13. How to get a piece level (more...)
  14. How about acupuncture to cure "carver's elbow"? (more...)
I need to learn what it takes to carve something thin and free, like a curved arm, or a finger. Also undercuts like in textile folds, without breaking them.
I work mainly in marble, which is I think more brittle than sandstone or limestone. (top)
So, you only want to do the most difficult things ;-)
There's a couple of points I can make, but you probably know them already:
I'm presently working on a dry stack wall. It's challenging and fun to shape the stones to fit each other. I think my tools are more than sufficient but I'm having pain in mainly my striking forearm and elbow. I have a 2, 3, and 4lb hammer. (top)
Unless you are very strong and experienced: don't use the heavier hammers. Battleing with stone, you don't win by force, but with patience. A couple of smaller strikes add up and are usually less tiring then big blows. I know of small lady sculptors working with a 500 or 700gr Hammer quit efficiently.
I understand that you are trying to shape the stones, making top and bottom flat. Are you doing that while building the wall? In that case, you'll probably work in an awkward position and without a solid table or such, meaning that a lot of energy from your strike is not converted in stone shattering but e.g. making a hole in the ground, displacing the stone etc.
It is heavy on the muscles also when you have to hold the hammer in a horizontal position. Your position should allow you to hold the hammer very lightly, not clamp it, and close to your body, the head pointing upward from your hand (not sideways excerting a torsion-force even when not swinging).
I'm sure the angle of the strike varies considerably by what you are trying to accomplish but are there any guidelines you could give me that might help me be more efficient? (top)
Wenn using a pointed chissel, there are two techniques:
1. Almost perpendicular to the stone surface; it works like a 1-pointed bush hammer. Evening out a surface consists of randomly placing the chissel on the surfaces that are above level.
2. At an angle of 50-70 degrees, depending on the stone. When striking the chissel, it should move only a little (1-3mm) along the surface, most of the force should go into the stone. When to steep, the point doesn't move at all and just bites deeper into the stone. When to shallow, the point just scratches the surface. Make parallel furrows over the above level surfaces and repeat the process overlaying the furrowed surface with new furrows in another more or less perpendicular direction (the second layer of furrows is easier than the first, as the surface has been weakened already).
Try to feel and hear the difference of different angles, as the most efficient angle depends on the kind of stone, your chissel point etc. Let every blow count, placing them precisely (speed will come with practice, hammering to fast and imprecise just wastes energy). If flakes don't come off at least every three or four blows, adjust angle.
When using a pitching tool, there's only one angle: perpendicular to the surface; the angled working surface of the tool wouldn't make sense otherwise.
To split off surfaces one can, depending on the stone and its layerdness, also use a tracer: also usually perpendicular, place it along a straight line where you want to stone to split. Hit, reposition along the line, hit againi etc. At the end of the line, repeat. As every hit adds to the growing fracture, even small blows or thick stone will eventually split.
Dust, ist it really dangerous? (top)
It's worse than cigarettes: I know of a sandstone-quarry where the workers died at an average age of 32, the maximum being 35 years old (Bad Bentheim, Germany, beginning of the last century)
I'm not a doctor, nor a lawer. Anyway:
The trouble with any type of health-prevention method is that you don't know if you, as an individual, could have gotten by just fine without it. You take precautions, because the risks are to high otherwise.
My teacher used to tell me that marble and alabaster dust (chalk and gipsum) is somewhat less dangerous than silica-dust. The first two just clog up the lungs but can, in small quantities, be dealt with by the body. Silica-dust (from stones like soapstone, sandstone and granit) can't be dealt with by the body and is chemically more active: it scares the lungs. Then again: marble-like stones can contain other minerals and alabaster can contain clay-like veins (which again is mainly silica).
Asbestos, on the other hand, chronically irritates cells in the lungs because of its very fine fiber-structure and can cause cancer. The probability of getting cancer is dependent on the dose and the type of asbestos, but there is no minimum dose known, below which you can't get cancer from asbestos. Asbestos is found in/with serpentine and soapstone.
Apart from asbestos, the dose of dust makes the poison. If you are a sculptor and work in a dusty enviroment almost every day, you should definitely take professional dust-protection measures. If you see dust hanging around and/or work in a cloud of dust, chances are that air masks are only partly effective in protecting you from that dust (read the fine print about dust sizes and the ppm the mask is supposed to protect from). And anyway, the really dangerous dust-partikels are the ones that are so small, you cannot see them. They travel deep in the lungs and are generally not removed by the flow of lung-mucus and coughing.
An ordinairy fan blowing dust away will also cause turbulence, making dust swirl around an coming back to you. What you want is a laminar (parallel) flow, preferably downwards, working together with gravity and a filter before the air gets free again.
Preventing dust getting in the air, e.g. by grinding wet, might be a good idea, if you have the money for the machines and the workplace adaptations.
I won't advise you on what are sensible precautions, and what might be to much. I myself work outside as much as possible, wear a class P3 dustmask almost all the time (outside also, especially when using grinding machines and the like) and will only work with serpentine and soapstone after they tested negative for asbestos.
Could you supply the name of the place where you get the stone tested for asbestos (top)
Sure,
Fibrecount Asbest Advies & Laboratorium, Cairostraat 129, 3047 BB Rotterdam, Netherlands, http://www.fibrecount.com
In 2001 (my last contact with them), they offered to test any small stone sample for fl. 55 (about 20 EUR) sent to them by postal mail. They use a McCrone test (polarisation in an oil-saturated sample) reporting presence, type and mass-percentage of asbestos. I'm sure a geology-department near you can do the same.
In 2001 I wrote a (dutch) webpage about asbestos and serpentine http://ergoarte.ch/arte/text/20010806/serpentijn.html
Quick summary: Asbestos is found as veins and is a fibrous cristal-form of the mineral crisotile. Crisotile, in a more harmless form, is often a component of serpentine. I couldn't find information about how asbestos is distributed in a quarry, meaning one should test every stone to be on the safe side as long as the quarry doesn't have some independent, written proof of being completely asbestos-free.
The whole research was triggered by the claim of a vendor who said he sold certified asbestos-free serpentine but wouldn't show the test-report or tell about the testing- and sampling-method used....
What (not) to look for in angle grinders (top)
For cutting, you will probably only use full-speed. For grinding/polishing you might have to work at lower speeds because of the specifications on the grinding material.
Depending on the quality of your machine, it might vibrate less when not working at full speed.
Depending on the size of your hands, take care to buy a model that you can hold comfortably for a long time. The cheaper ones often have a rather fat body and are heavier. They also tend to get hot enough to melt the plastic parts inside used for the power-switch.
Some experiences with safety (not a full list! use your own brain please! (top)
  1. wear sturdy gloves, they once saved me from a crushed thumb
  2. wear steel-nosed shoes, they could have saved me from a somewhat damaged toe
  3. never try to catch a falling stone or sculpture, just get out of the way (instruct unexperienced helpers to do the same)
  4. check with your insurance company (health, liability) for you and your helpers. ("Sir, you willingly took on a foolish risk in moving that stone, surely we cannot be expected to cover that")
  5. never hurry, only then tomorrow there will be another day
How I move stones up to 2000kg (top)
I have most of my stones on pallets and have a pallet-trolly (is it called that? a low hydraulic rolling thing to lift and roll the pallet). I constructed my workbenches so that I can also move them around with the pallet-trolly. Comes in handy when giving courses. The trolley needs paved, even ground, though. To lift stones out in the open (e.g. onto a pallet) I use a long (1.5m) sort of crowbar and many pieces of wood to lift the stone a little, slip a piece under it and repeat till the right height has been reached. In the workshop I have a pulley. On the wishlist is a portable gantry crane to more easily place sculptures outside and on soft ground.
It's fun playing with big stones.
Dust cannot be that dangerous, can it? Only anecdotal: I've known dozens of carvers and cutters who were older than 70, some of whom were still actively working (top)
I'm sorry to be so direct, but you're not so likely to know people that died 20 or 40 years ago, are you ?
Do wear good protection. Perhaps marble-dust doesn't clog the lungs as fast as silica-dust and perhaps it is not as chemicaly active and causes somewhat less scarring. But lungs cannot be repaired by medicine if you gambled wrongly. Spent a little time finding out what masks do fit and are not to uncomfortable and get used to it. The sooner you do not concentrate on how the mask feels, the sooner wearing it becomes a habit and you forget about it. BTW, regular cleaning/desinfecting of mask and its straps helps prevent skin irritations.
As to statistics: what answer would you be looking for? In Bad Bentheim, Germany no man (all working the sandstone-quarries) lived a day over 35, average age 32. So even if marbledust is 95% safer, it would kill one in 20... What if you don't die, but "just" develop emphysema? Visit some people with that disease: would you even want to take a one in a 1000 chance of emphysema?
Need for gloves: Maybe it's just me but I sometimes miss the chisel, and as a result I have a bone spur on my index finger knuckle which I've cracked with my hammer many a time. Does anyone know if there are special "armoured" gloves on the market that I could buy, to help soften the blows? (top)
Perhaps you're thinking the wrong way round? You should not hit your hand in the first place ;-)
I tend to hit my hand when I'm tired, when using a hammer that is to heavy or both. I'm not comfortable using square mallets, they don't have as much balance as round mallets ( See: http://de.wikipedia.org/wiki/Bild:Knöpfel-3.jpg Also, they don't hurt as much, as they are blunt in any direction. The grip should fit comfortable in your hand: to small leads to cramps and less control.
With pupils, I often see them moving the chisel during the blow - that's also not good. Try to analyze why you are hitting your hand.
I have to polish flat and curved pieces, I guess one of the most difficult things is knowing how much pressure to use. But I guess that comes with practice, also how much water, a stream or a trickle. (top)
I usually work dry. The water is there to take away the heat from the friction. That should give a clue: to little water and you will see the stone drying because of residual heat. To much water and you get aquaplaning :-)
As to pressure: the abrasives, especially diamond, don't need/tolerate that much pressure. Working with a flex on a horizontal surface, the weight of the machine is enough pressure (just a few kilogramms). Let the rotational speed be enough and the pressure be light enough so that the machine doesn't start wheeling away.
Polishing: I do go up all the grits slowly, but with the wet surface i find it difficult to see if I have done enough! (top)
Pause between grits and let part of the stone dry, before deciding to use a smaller grit is what I do. Don't hurry through the grits, better use the coarser grit double the time, especialy the first grit.
After each grit size, the next one will need less time.
How to get a piece level (top)
Bit difficult to explain in writing: Put the piece level as if in the final, intended position. Draw a horizontal line on the piece as a reference near the bottom, starting where the stone is furthest away from the ground. Draw the line all the way round, using e.g. a piece of wood as a guide. Remove all the stone below the line.
How about acupuncture to cure "carver's elbow"? (top)
Acupuncture won't cure, that is something the body has to do for itself and it takes a long time when tendons are involved. It may take months, rather than weeks, also depending on your own behaviour.
There are three traps trying to cope with a carver's elbow:
  1. Doing nothing but resting the arm: that slows healing and makes you generally weak.
  2. Taking pain medication/acupunture and working (almost) normally: the pain was your body telling you that you are working too much or in the wrong way. Suppressing the pain means real damage will probably take place, you just won't notice it that much.
  3. Injecting corticosteroids: they relieve the pain and destroy the tissues that should be growing stronger.
If you have a good doctor, go see him/her to check for possible other causes. A friend of mine discovered, after a year of pain, that carving wasn't the most important source, but writing on a laptop on a badly fitted desk was.
Seek advice from an occupational therapist that has experience in evaluating working environments. It may be something in the way you work, hold your machinery, (don't) take breaks or how your workplace is furbished.

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Gyelt Tuinstra