Hey! Here’s my interview with David Williams, author of Stories in Stone. It’s a fantastic book – full of interesting stories about the stone used in the cities of the US. For the techno-geek, there are plenty of details about the technology used to acquire and transport the stone. In keeping with my interests in technology and its history, David was good enough to do a virtual interview. Read on for the Q&A! And post any comments you have. We’d love to hear what you have to say.
Q What do you consider the most remarkable innovations to be for ‘harvesting’ the stone?
A One of my goals in the book was to try and answer this question. To do so, I went to quarries and stone yards across the U.S. and in Italy. The answer is simple: the advent of industrial diamonds has changed the face of quarrying. In the past, steel, often as a braided wire, would be used to cut stone. Steel has several negatives. It is not as hard as granite so slicing rock required a sand-slurry to enhance cutting. Additionally, whether harder or not, steel cables could get very hot while cutting, which required the use of lots of water and often very long cables. These long cables gave time for the steel to cool down before it had to cut again.
Steel is still used but now most cutting and polishing tools are impregnated with tiny diamonds, which can cut faster and with less heat build up, though water is still required to keep things cool. The new tools are much safer, too, because there is no longer the chance of steel cable, which could be thousands of feet long, breaking and uncontrollably whipping around a quarry yard.Q – What about for transporting the stone?
AVery, very large wheeled-machines, such as trucks and front-end loaders revolutionized quarrying. As I discussed in several chapters, in the old days, quarrymen historically moved stone with a derrick and pulley system. Derricks required several men to work them and could be dangerous; if the cable broke a multi-ton block would drop and crush anything in its way. Prior to derricks much of the transport involved moving blocks with ropes and logs, a process that lead to two, massive marble columns almost killing Michelangelo. Now, men (I use this pronoun because there are hardly any woman in the quarry industry) load and move all stone with wheeled vehicles.Q Are any of the techniques for acquiring the stone you describe still in use today?
A The plug-and-feather process has been in use for several thousand years. This involves drilling a row of holes in the rock and driving in wedges to split the rock along the row. If you look at many stone buildings, particularly older ones, you may encounter these holes, which are six to eight inches deep and always extend down from the edge of a rock. Oddly, even though the Egyptians used the plug-and-feather process, it wasn’t introduced into the United States until 1803, when a Mr. Tarbox used it in Salem, Massachusetts. He features prominently in my chapter on the Quincy granite.Q Have these techniques been modified to keep up with advances in technology?
A The main modifications again are in the machinery. When Mr. Tarbox made his holes, he used a hand tool, more akin to punching a hole than to drilling. After making the hole, he would drop in two shims (the feathers), bent at the top so they wouldn’t drop into the hole, and then place his wedge, or plug, and start pounding the plug in with a hammer.
Now, holes are drilled out with hydraulic drills. People still use the hammer for pounding in the plugs though some in the trade have introduced a hydraulic expander to force the stone apart. In the words of one older quarry owner, “We were a lot tougher back then.”Q Where does most of the stone in use today come from?
A I don’t know the statistics on who produces the most stone but stone can come from anywhere in the world. The U.S. still generates great amounts of granite and limestone but much less slate and marble than in the past. And, of course, China and India are producing stone.
Q How is this stone acquired?
AI am not up to date on China and India but have talked to people who have seen quarrying operations there and much of it is done by hand with people pounding lots of steel. For more developed areas, most stone is cut with diamond saws.Q How is this stone transported?
A Train, truck, and boat. It took 100 boatloads of stone shipped from Italy to provide the travertine at the Getty Museum in Los Angeles. Transportation has long been a key part of the process. The first commercial railroad in the United States, in Quincy, Mass., developed to move stone for the Bunker Hill Monument. In most places, people started with local stone because that was the easiest to transport but now with modern means, any stone from any where can end up at a work site. It is nice for geologists and architects though perhaps not so great for the planet.
Q Is there any exciting innovation coming up on the technology/transportation horizon?
A Not that I know of though when I was visiting a stone yard in Minnesota I did see a machine that used a jet of water to cut stone. The water shot out at over 900-mph at pressures of up 60,000 pounds per square inch and could cut a 4-inch thick slab of stone. That was pretty cool though water jets are more for precision work than large scale cutting. And in regard to transport, moving stone is simply a matter of battling gravity and trucks are great at moving dead weight.