US scythe enthusiast Benjamin Bouchard posted a scan of an old brochure he came across, onto the scything improver’s forum. It was produced in 1915 by the Pike Manufacturing Company, one of the largest makers of abrasives in the US.
I was intrigued – and rather dubious – about their claim that the production of Arkansas whetstones involves 90% waste. It’s obviously of benefit to a manufacturing company to herald the advantages of the ‘new kid on the block’ – synthetic abrasive – since it doesn’t incur the overheads of mining and cutting stone, and it seemed likely to me that this was a bit of hyperbole (“the story of the Arkansas stone from the time it is taken from the earth until it leaves the factory as a finished product is a story of waste” – from the caption of a photo of a voluminous waste pile) to convince readers that synthetics are the way of the future.
Before I go further, I should say that in most cases I would agree that synthetic materials are superior to their natural counterparts – including in whetstones – in terms of performance and quality. This is simply because synthetics are purpose-built, while natural substances are typically harnessed because they have one or two properties that are outstanding in the most often encountered situations, but fail dismally in others. In the case of whetstones, the chief advantages offered by synthetics are consistency and ‘tailoring’ – the ability to choose and combine particles and bondings to behave as required.
There are some natural whetstones that have quite remarkable properties (e.g. coticule, which has an enormous range of ‘grit rating’ depending upon how it is used) although, again, these could be replicated by manufacturers if they were deemed to be of enough utility (or, perhaps more importantly, saleability) to warrant the research and development to produce them.
It’s likely that cost of production of synthetics is also dramatically lower, although I haven’t read about or discussed this enough to know the real situation (although I do know that the wholesale price of some well-respected natural whetstones is lower than the wholesale price of well-respected synthetic stones), and this brings me to the broader, non-performance aspects of synthetics – I simply don’t know what’s involved in making them, in terms of how the raw materials are sourced/produced, how much transport is involved, how much energy is used in their production, what chemicals are utilised, whether there are any gaseous/solid/liquid by-products, and so on. So even if a natural stone quarry does produce 90% waste, that alone would not be enough to sway me that moving to synthetics would be “better”.
For me personally, the availability of natural whetstones is also something that is unlikely to ever be matched by a synthetic. It’s arguably not a performance measure, but then, it kind of is… when it comes to getting my edge sharp, my bit of softish, inconsistent sandstone beats any synthetic that I can’t actually lay my hand on; most folks can probably take a stroll and find something that would render an edge sharper if used sensibly, and most of us are unlikely to ever be able to concoct a synthetic whetstone.
But, back to Pike. I decided I’d do a little test of my own. Having slabbed a smallish rock – a little smaller than the size of my laptop computer – into whetstone-sized slices, I put it on the scales. It came in at just over 5kg. Of course, by this time I’d already wasted some of the stone with the diamond saw kerf. I planned to use Archimedes’ Principle to work out the volume of the remaining stone and so calculate what I’d already wasted, but I got distracted by something for more than 5 seconds so forgot to do that before I went back to making them. So I’ll just note that I made 8 cuts, and I’ll allow for a cut 5mm wide (which is generous). Working at 13mm for an average width of the whetstones, I wasted 8×5/13 = 3.1 whetstones with the cutting (again, I think this being conservative).
With each of those 7 slabs cut and ground to whetstones, I popped them back on the scales. I was actually very surprised to see that I now only had just over 2kg. i.e. 3kg of that 5kg stone has been wasted.
But, on closer inspection I’ve noticed that I can just get another whetstone out of the longer of the two outside pieces I’d cut. I haven’t cut that last one yet, so just assuming an average whetstone weight of 2.045/7 = 292g, that brings my total usage up to 2.337kg. If we add the 3.1 wasted whetstones lost in saw kerf, we end up with an original rock weight of (3.1 x 0.292)+5.075 = 5.98kg.
So I’ve produced 2.337 kg of whetstones from 5.98kg, meaning I’ve got 61% wastage.
I actually find that staggeringly high; making 8 whetstones from that one relatively small rock is, to me at least, intuitively a very effective use of resources – and a few hours well-spent! Even if I completely remove the saw kerf allowance, it’s still 54% wastage.
I could reduce the waste by cutting the final edge into rectangular pocket stones for a pocket knife or similar (and I eventually will – looking at it I reckon I’ll get four of them out of it). And of course the canoe shape makes waste inevitable. With larger rocks I can arrange the canoes in an offset/interlocking manner to reduce that waste, but in this case I was only using a small rock. And there are also cases where I find that, due to a fault or flaw, I may only get one whetstone from this size of rock. Or I may cut into a rock and discover that it’s actually a completely different kind of rock and not suited for whetstones at all.
So, on that basis – considering every rock collected – an average wastage of 90% doesn’t seem so outlandish. But then again, I’m prospecting – picking up rocks – not quarrying, as Pike was. Pike’s scythestone quarry was sandstone in definite layers. It’s highly unlikely that they’d retrieve a slab of sandstone to discover it was unusable, because the quarry was basically one enormous lump of usable sandstone, in layers. Neither, though, was Pike making scythe stones from Arkansas stone, which is what their 90% wastage figure was attributed to.
In short, then, I think my initial objection to the 90% figure (which was that if it’s really that high, it’s a function of the rock they’re choosing to use) stands. Based on that surprising 61% wastage figure above, our own average wastage figure may indeed be 90%, and that would be significantly attributable to the fact that we’re dealing with small rocks, and qualities and compositions unknown until they go under the saw.
We should, of course, actually consider what “waste” means. In my case, I’d say I’m not really wasting anything. I’ve now got a crude sluice set up so that the water and rock dust that comes off the saw goes into a bucket. I sprinkle that onto the soil in my crops to return some minerals back to the system. The offcuts that are large enough to do “something” with, I have set aside in a pile (I’ve made two gifts with them, and a bench stone, so far, and will eventually get around to cutting some pocket stones). The offcuts that are too small to be useful are filling potholes in bush tracks. So whether anything is really being wasted is arguable, and that enormous pile of “waste” at the Pike yard could surely be put to use somewhere (as I would expect it was, at some point).
It would be interesting to know what waste is produced from the synthetic processes.
Errata: while doing the dishes I realised that I’ve underestimated wastage by using the weight of whetstones to estimate what was lost in the saw kerf. But I lost the whetstones AND the part of the slab not used in the whetstones. Perhaps this may even out my generous allowance of 5mm for the saw kerf, but I suspect that I’ve actually underestimated wastage slightly.