Even French stones are better!?

I’ve been nose deep in the history of forks in Colonial America, so I’m possibly a tad stuck on the strange things that Americans have imported over the last three hundred years. This is possibly one of the stranger imports I’ve seen lately.

In the 18th and 19th centuries it was common for American farmers and millers to import a specific stone, known as French buhr, for the crafting of millstones. The vast majority of these stones seem to have come from the regions surrounding France and it was believed that millstones crafted from French buhr ground a superior wheat product.

French buhr millstone

I first found out about this little quirk of American milling here, from a ScienceDaily article detailing work being done in Ohio to identify millstones that had been shipped in from France. The internet being the rabbit hole that it is, I eventually found myself at Penn State’s Medieval Technology and American History site(found here), where a few of the finer details of the older milling processes were highlighted with an explanation of what makes a better millstone. As with most tools for production its stone hardness, if the vanes carved into the stone became dull the grind would be coarser resulting in a wheat flour that would ferment faster.

Why the French buhr stones were preferred I’m not entirely sure of, yet. However, I see an excellent opportunity for some experimental archaeology…

16 thoughts on “Even French stones are better!?

  1. This is to Michael Patterson. Come to the Mingus Mill in the Great Smoky Mountains Park. We have a scrubber (called a smut machine) and a bolting machine still in place but not in use. The only stone we use now is for producing cornmeal on a set of granite stones that were quarried locally. We have French stones as well but they are not in production. Our mill was built in 1886 with a turbine that was manufactured by the Leffel Company of Springfield, Ohio. The mill is open daily from April 1 through October and then on long weekends (Friday, Saturday, Sunday) in November. After that we shut down for the winter. This was a custom mill where the farmers brought in their grain and the miller charged a portion of the raw grain as his fee, turning out the rest directly back to the farmer. he mill operated commercially until the National Park Service took it over in the early 1930’s. It was then run part time by the NPS until 1941 when closed down because of WW II. It was reopened in the mid 1960’s and has been open since. Most of the equipment is still in place though we operate only the stones (original equipment) and the turbine (also original equipment) to produce cornmeal for demonstration and for use as animal feed at the early farm museum run by the NPS. If you get to Cherokee North Carolina, come by and check it out.

    • Luther Jones, thank you for remembering me. I certainly will get down that way. I would very much like to see your scrubber and bolting machine as well as the turbine and mill stones. Looking forward to it.
      If possible, I will still try to make it this November, 2019. Otherwise, next Spring. This Sunday (10/27/2019) is our last day of Cider Festival at Historic Bowens Mills where I volunteer. We have been blessed with nice weather thus far! We’re only open now on Sundays in October for milling demonstrations and a few school field trips, otherwise weddings have become the bread and butter fund raisers for the private owners.

  2. G’day from Australia. This is a most interesting discussion and I am glad i chanced upon your site.
    My Great Grandfather a master miller, who emigrated to South Australia from Silesia in 1857 and established the first mill in Eudunda, a small town the the South Australian wheatbelt.
    His was steam driven mill with two sets of stones. The mill operated from 1872 to 1889 when there was an boiler explosion that caused significant damage. The old man had passed away by then and his sons sold the place to another milling company but continued in the business in another town with a roller mill.
    The mill stones have been used by the purchasing company as a door step at their residence, so at least they haven’t ended up at the local dump.
    I would say from having looked at the closely the are french stones though I believe there were some very good stones produced in Scotland at that time.
    Nice to be a part of the discussion.


    Les Newman

  3. It is my understanding that the French Buhr Stone is harder than granite stones. The French Buhr is actually Fresh Water Quartz from information I’ve read. They cost three times more but also lasted three times longer which was about 100 years. Because these stones were so hard, they were able to keep the sharp cutting edge of the furrows much longer than granite stones.

    • The French Buhr stones are such a small part of today’s economy that there appearss to be only a little information about them.
      The stones are a peculiar type of fresh water quartz that is found in association with fresh water limiestone. Both the limestone and the quartz are depositional stone. That is that the liimestone was dissolved by slightly varbonic acid. In a slightly different PH, temperature or pressure the acid water could dissolve or deposit these two materials in a new location.. The period of geological time is Tertiary folowing the Cretaceous period.
      French Buhr.
      French Buhr Stone is nearly pure quartz but it’s crystals are exceedingly small, called crypto crystaline. It is a variation of chert very similar to flint. French Buhr can be identified by looking for tiny fossils from a freshwater algae. A few fresh water snails may also be seen.
      French Buhr is found in the Paris Basin. There have been stones that seem to be as good as Frfench Buhr found in England and North America but in actual use very few serve as well as the French Buhr.
      French Buhr has several Characteristics which made it to be worth more than mopst other millstone materials. Millstone and Milling technology changed in the 1860’s and 1870″s which left the French Buhr high and dry in the milling industry.
      There is a lot of “In the cracks” information to be talked about. Maybe later. Jon deNeui

      • Good information Jon! I only know what I’ve been able to read in milling books. I volunteer at an old grist mill in Michigan that has French Buhr stones original from 1864. We demonstrations in the Fall and school groups whenever. Your information will be good to know, thank you Sir!!

        • Check Motor Mill for more background. We have seven or eight docents helping visitors at the mill. I noticed that there were six or seven different explanations of the mill stoens. I decided uncover as much info as I could about the millstones. I found thast most of the info was about the use of the stones but no explanation of the reason the stones were so desireable. There was very little current info specifically about the stones. French Buhr stones appear in just a couple of contemporary books. The info in the geology books gave clues but lettle help. The books specifically identified the stone as “Cellular Freshwater Quartz.” Tt was commonly found in the company of freshwater limestone.Cellular, led me to cel phones. Fresh water Quartz led nowhere, and freshwater limestone led me to a lake residential development in Texas. Somewhere I found a reference to the Paris Basin. which was productive in opening the provenance of our quartz stone. I also found similar descriptions about chert.

          I have found a lot of directly and indirectly info related info about the French Buhr following this pair of areas.

          Rather than go on and on I would be aided in sorting out my ideas if you could direct my discourse by asking questions. Thanks. JdN

        • Jon, yes your information is valuable to know. The mill I volunteer at is Bowen’s Mills in Middleville, Michigan. The mill stones are still the original but only have enough “life” for simple demonstrations producing corn meal. I haven’t any questions at this time but thought you may find this book of interest. “The Millstone Industry” A Summary of Research on Quarries and Producers in the United States, Europe and Elsewhere. After reading through this book, I have concluded that unless one knows how to identify minerals, a buhr stone may come from a number of locations besides France and made of one of several types of minerals that looked and acted like the French Buhr stones. The stones in Bowen’s Mills date from 1864, so they could be from France, Georgia, North Carolina or Ohio??? When I first came to this Mill, they told me the stones were made of Coral. I’ve never heard or read any information on Coral Mill Stones. First off, I can’t imagine how they would ever harvest Coral in those days!! Through my own research, I discovered the Quartz stone and concluded they must have mistaken Quartz for Coral.

        • I’m gratiafied that people are wanting to knnow more about the Buhr Stones. The basic family of rock that the French Buhr Stones comes from is in the Chert family. The French millstone builders that laid claim to the ultimate millstone material claimed that they were the best that could be bought. Chert arises as a chemical deposit sedimentary rock that began to be formed when the earth cooled enough to have liquid water flowing across and through the rock and decomposed rock of the earliest times. It is likely that chert is still being formed. The chert of the Paris Basin thats was called French Buhr Stone was formed in the days of the tertiary period in fresh water. The desireable qualities were extreme hardness for long wearing stones, extreme toughness arising from the crystaline structure being a conbination of microscopic or sub microscopic crystals with no cleavage planes and tiny silicon dioxide rods that formed a stone that was extremely resistant to breaking or chipping. The cellular structure was also a factor where the irregularly shaped and sized holes were credited with a superior wheat flour milling capabilities The chert is silicon dioxide which can be shaped to good precision by chipping and powdering the glass-like material. French Buhr stones are usually identified by the occasional fresh-water snail shells and the presence of silificed fossils of the seed like strucures of a fresh water algae. There are numerous deposits of Chert in the appalacians and other places around the world which could be made into mill stones. The french didn’t give up their claims to superiority until the milling technology orphaned the French Buhr Stone productds. In the peak years of these millstones The french marketed finished millstones as well as blank stones to be manufactured elsewhere. Ohio seems to have been a millstone building are uising local chert deposits as well as imported French Buhr to meed the demand in the US for top quality mill stones. Businesses building millstones from other stones were certainly sure that their products mesured up well against the imported goods.

          At Motor Mill we have four original bed stones in place where they were originally installed. The mill was in commercial production from 1870 to1995 when the partnership was desolved and the mill became a farm facility. There probably was some milling being done in the mill. The bed stones show a polish from the wheat being milled. All milling stopped when the dam was destroyed by a flood. We’re still looking for mention of that event. The runner stones were removed from the building and a couple of years ago a family approached us to donate a runner stone. Their family tradition had that this runner stone was originally form Motor Mill. It may be. I can make no predictions on when we will try to remount this stone.

          I started looking for more factual or reputed factual info when I noticed that our tour guides were following a dozen different explanations in their talking to visitors. JdN

        • Jon,
          Very informative on the creation of these stones. You mentioned something that peaked my interest. You said your stones have a polish to them from milling wheat. In Bowen’s Mills, there are two sets of stones. One is still working however, the other set is non-operational, also due to a dam breaking in 1943. This set now sits un-even and the gears were also shattered during the event. I have volunteered here for nearly 15 years now I guess and just last Fall I noticed the non-working set is polished yet no visible signs of furrows. I was planning on researching this a bit. Surprising, no visitor has ever asked about this yet! My research indicated furrows were needed for distribution, ventilation and for cutting or slicing the grain. So my question to you Jon, are your stones flat and polished or do they have furrows and a polish? The working set has the typical cycle pattern but I never noticed any polish when we clean them. Since the stones are so worn down, the owner doesn’t feel it wise to dress the wheels. They do a good job demonstrating the milling of corn meal. I try to gain some new and fresh insight each year to tell visitors. Again, your information will be good to know. Thanks! We are only open for six weeks in the Fall and on special tour groups. The Spring and Summer season’s are for wedding’s on the grounds – that’s what pays the bills!!

        • This will be a discussion of the surfaces of rotating mill stones. The pattern of fu rrows and lands was mainly the choice of the Miller. His preferred pattern probably came from his apprenticeship or other training and experience. Early in this technology it was discovered or learned that different kinds of rock used for millstones worked better or worse than the fineness of the rock itself. Millstones of the middle ages and renaissance came from locations where the better stone materials were quarried. For example Cologne was a source of millstones cut in one piece from lava rock. These Cullen stones had a moderate crystal grain which presented harder and softer material which as the softer was worn by the grain the harder crystals stayed ijn place. This surface texture improved the milling process except that the hasrd grains would break free and join the flour being milled. The milling surface was improved by hatching wich basically was a fine crosshatch chiseled into the stone, increasing the capacity of the flour grinding. Another aspect of the millstones was the development of furrows and lands. The patterns of these grooves and flat areas had the effect of moving the grain between the stones from the center to the perimeter. The grist proceeded from introductory whole grain stage to the finely ground output stage. The furrows are seen as tlhe sharp drop and slanted surface across each f;urnow. These furrows function as the mover of the grist across the stone faces and out at the perimeter. The slanted sufrace of the f;urrow acts as a ramp, moving grain into the surfaces of the lands. The actual grinding of the flour happens between the lands of the upper and lower mill stones. The flat areas between the furrows was where the grain was ruabbed and crushed. This is where the hatching of the surface paid off. Just about all the millstones not made of French Buhr had to be hatched to have an improved milling surface. So the periodic maintenance of millstones involved frequent hatching the lands. Thje furrows had a deeper profile and had to be recut only when the land surface wore or was hatched away.
          French Buhr of good quality was a quartz stone that had numerous and variable cavities or cells. Millers seem to have believed that as the lands of the French Buhr mill stones wore, New edges around the cells would be like broken glass edges. It was believed that the wheat grains being milled were cut on these sharp edges which made the milling much easier. Cullen or Cologne stones needed to be set to an almost contact spacinag. The French Buhr stones milled wheat with a greater space, usually about the thickness of Kraft paper. The grist between a pair of Cullen stones had to be ground by crushing and rubbing. This had two disadvantages, one ws that the seed coat or bran was ground just as fine as the wheat endosperm. The bran was very hard to separate from the flour. This reduced the producxtion quantities and raised the price.
          The greater clearance between upper and lower French Buhr stones allowed the wheat to be rolled to loosen the bran and then allowed the resulting bran to not be ground to fine powder of the same size as the flour particles. Fine white flour could be easily separated from the bran, increasing productivity and reducing production costs. Another advantage of the French Buhr stones was that the greater clearance between the runner stone and the bed stone reduced the friction and the heat generated by the friction. The French Buhr stones could run at higher speeds allowed because the frictional heating was reduced. This was less harmful to the gluten which made the fine white bread and cakes possible. Cooling of the warm or hot freshly made flour was a critical factor in getting the best qualiy product.
          The increased clearance between the French Buhr stones reduced the stone to stone contact which wore other kinds of stones down. The polish on the Motor mill stones mentioned is a degree of smoothness created by the wear of the grain and flour and didn[t ingerfere with the cutting action in the cavities in the French Buhr stones. These millstones didn’t require hatching as frequently and the wear from stones in contact was reduced consicderably. Some millng authorities believed that a set of French Buhr stones were almost a lifetime investment. Motor Mill was in production for ablut fifteen years from 1870 to1885. The Motor mill stones were still practically brand new when they were stopped.
          Time to stop for now. Thanks for asking. JdN

        • Jon, thank you for all your information and the time to reply to my questions. Thanks to Sara Gonzalez for your work and allowing Jon and myself to use your space for chatting. Jon, if I should get out your way, I will definitely look up Motor Mill. I was expert in the basics but now can go on to imparting more advance knowledge to those who may want to know more (far and few it seems). My next research will go into the workings of the upper floors where grain was stored. The elevator brings the grain up and there is a machine called a scrubber I think?? I’ve only seen it in drawings. Sadly, very few people ask questions however, I would like to know myself. I like to be prepared. Most of what I’ve learned is from reading from a couple books and on-line research. Your information was most advanced from other sources on the minerals of the stones. Thank you Sir!

        • Wow! “Sir”! You made my week. I must tell you that after I joined the Motor Mill Board of directors it took about two meetings before the Jon rule was applied. Now at a board meeting, everyone else gets to talk before I get my turn. It seems to work better that way.
          I dug into the millstone area because I wasn’t confortable with different explanations being given. It became a private swamp that I could go and roll around in and discover the separate but blendable info.
          Motor Mill was in business as a merchalnt mill making flour in bulk quantities for shipment to the big citiy bakers. It began producing flour in 1870 and by 1885 was belly up. At that point the saleable assets including the eight-story mill, the cooperage, the inn, the liverystable barn and the icehouse/smokehouse were aucdtioned off. The machinery in the mill was either sold or left for scrap.. The third and fourth floors were removed to make hay storage so all traces of flour refining machinery and the power system are no longer there. We have this fantastic space resource with no clues about anything except four bed stones in situ and a machine on the fifth floor called a smutter. The challenge will to be in adapting the buildings to a use that will make us a destination for visitors. The DNR won’t let us build a dam on the Turkey River so the water power based system in the mill won’t be a likely projecct. Please keep us in mind for visiting. I think you’ll be surprised at the visiting points we have fun showing off.
          Ask more questions. I really enjoy putting my thoughts in order to make an answer. I guess I am the structural and builoding manager so I’ve got lots of thoughts and ideas about what we can see or discover. JdN

  4. The four bed stones at our historical site are still in the oritinal places in the mill. I found that there were nearly as many explanations as there were tour guides. In order to provide a more reliable explanation of the stones and their operation I have spent time studying French Buhr Stone mill stones. The buhr stones make superior mill stones because of the hardness and toughness of the qryptocrystaline silica. The hardness meant that hey wear slower than other stones and the toughness reduced the frequecy that any pieces or chunks broke loose during operation. Grit wasn’t a good thing to find in your bread.
    French Buhr stones are made from freshwater chert. There were man;y attempts to duplicate these using marine chert. Marine chert wears faster than the stone of the French Buhr. Another peculiasrity of any of the chert stones is the random voids or cavitries in both th;e freshwater and marine varieties. These generally small voids range in size and frequency. Millers wanting to grind fine white flour found that the French Buhr stone could be made and refined to produce the fine white flour called for for baking fine bread and cakes. The belief was that the cavities even tiny ones ground wheat to a fine powder without grinding the wheat bran as finlye. The larger bran particles coule be separated from the flour in the bolters of the mill. Bran in the flour makes the bread and cakes turn out heavier and darker color. Millers believed that as the mill stone surface wore, the exposed edges of th;e voids were continuously made sharp. This meant that the wheat was cut rather than crushed. In all milling process heat is generated by the friction between the faces of the stones. Too much or too loing heat in the millage degrades the gluten. Gluten is what gives the flour the ability to rise. The French Buhr millstones coulod make the basis for better flour even though the clearance could be set a bit farther apart. This ability to work well with more clearance between the stones allowed a higher rpm and could process the wheat faster. It also allowed the bran or seed coat of the wheat to come off in larger pieces that could be sifted out in the refining process of the fine white flour.. JdN

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