This article is from the 26th February 2026 Newsletter

DRESSING STONES AND JUST HOW MUCH STONE DO YOU EAT IN YOUR FLOUR?

Karen is now back from her winter holiday and she has managed to mill a stock of flour to cover a couple of days without milling. With this in mind and if you remember I covered the dressing of our base stone in a January Newsletter, we decided to have a go at dressing the runner stone.  This is slightly more involved than dressing the bed stone as we need to stand the stone on its edge to allow access to the grinding face. This must have been the normal method used in the past, because there is a large eye bolt through one of the major upper floor, floor beam just to the side of the stone. We built a wooden platform to stand the stone on and by judicious use of two chain hoists and an hydraulic jack, we eventually got it into position. The stone was dressed and then lowered back to its position.

THE MILLSTONE NEARLY VERTICAL READY FOR DRESSING.

So the question is how much stone actually wears off a stone when it is working and therefore ends up in your flour?

Luckily I have found a paper that tries to calculate it.

The calculations are for a 50 inch diameter French Burr Stone with a 12 inch eye (the hole in the centre through which the grain falls). Presuming that 6 inches are lost off each stone over the expected life of 50 years, this would be normal commercial rates, much higher than we do.

When grinding the stone is only lost from the Lands, the flat area on the stones between the grooves. The stone from the grooves is removed whilst dressing so doesn’t go into flour. Assuming the lands account for 50% of the surface then only half the stone is going to go into the flour.

On a commercial basis it was expected that stones would grind about 73 tons of flour between each dressing of the stone and the stone would loose a thickness of 0.32mm of stone doing this.  According to the paper this is equivalent to 0.0125gms per kilo of flour milled.

This will be very fine stone dust and not pieces that you are going to feel in your bread as you eat it.

Just as a mention we use French Burr Stones. If you buy flour made on typical Millstone Grit Stones, then they are softer and the amount of stone in your flour will be greater, according to the article about four times the amount.

Enjoy your bread.

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