unusual sharpening method

[bugbear]

From a 1945 article in woodworker, by a British Guy working with (employing, I think)
Indian carpenters:

Some use the ordinary oil stone, but many use a combination
of a piece of open grained timber, a stone of the flint species
which is ground into fine crystals, and a few drops of water.
The water and crystals are mixed to a rough paste, this
is thinly smeared on the timber, and the craftsman sharpens up.
After a time this improvised hone needs the paste treatment only
occasionally. The grain of the timber fills and makes a hard, black
surface which is strangely efficient.

I think the words "improvised" and "strangely" tell us more
about the author than the process.

BugBear

 

[lurker]

Jacob's Dad?
Just leg pulling Jacob :wink:

 

[lurker]

It's not a million miles from a sheet of mdf and Autosol is it?

 

[MIGNAL]

Perhaps rougher. More like valve grinding paste.

 

[bugbear]

Perhaps rougher. More like valve grinding paste.

It would depend how much the ground grit broke down in use.

Now we know the technique existed, it may be possible to find further details.

To quote Donald Rumsfeld it's now a "known unknown".

BugBear

 

[Fat ferret]

I got an old book with a photo of a man sat on an elephant apparently using a handful of sand on the beasts skin to sharpen a machete :shock: .

 

[Phil Pascoe]

Every time I read "known unknown" it reminds me of Brian Moore being asked about England's chances of winning the World Cup - "What are England's chances, Brian?" --- "I don't know, there are too many imponderables" --- "can you tell us exactly what these imponderables are?" --- "No ... because they wouldn't be imponderables then, would they?

 

[Cheshirechappie]

"....a stone of the flint species which is ground into fine crystals...."

Now there's a few simple words that covers a lot of labour. Flint isn't the easiest of materials to grind into anything, let alone fine crystals. I dare say an industrial process could be devised, but I suspect in this case, other, more labour intensive, methods were used.

That said, it's not that much different to any process involving abrasive particles held on a backing of some sort. Scary sharp? Diamond plates? Lapping? Same principle, different media and materials....

 

[Jacob]

"....a stone of the flint species which is ground into fine crystals...."

Now there's a few simple words that covers a lot of labour. Flint isn't the easiest of materials to grind into anything, let alone fine crystals. I dare say an industrial process could be devised, but I suspect in this case, other, more labour intensive, methods were used.........

Mother nature grinds up a lot of stone for us. It's very common around the whole world, and known (in Derbyshire at least) as "sand".
I didn't think using it for sharpening was particularly unusual - I'm really surprised!
It can be stuck to paper to form a practical abrasive known as "sand-paper" (in Derbyshire at least).

Jacob's Dad?
Just leg pulling Jacob :wink:

And your Dad, and his dad, his dad's dad etc going back to the early stone age - several million years

 

[Cheshirechappie]

"....a stone of the flint species which is ground into fine crystals...."

Now there's a few simple words that covers a lot of labour. Flint isn't the easiest of materials to grind into anything, let alone fine crystals. I dare say an industrial process could be devised, but I suspect in this case, other, more labour intensive, methods were used.........

Mother nature grinds up a lot of stone for us. It's very common around the whole world, and known (in Derbyshire at least) as "sand".
I didn't think using it for sharpening was particularly unusual - I'm really surprised!
It can be stuck to paper to form a practical abrasive known as "sand-paper" (in Derbyshire at least).

Well - if you can find any flints ground into fine crystals by mother nature, good luck to you.

 

[sdjp]

Flint isn't the easiest of materials to grind into anything, let alone fine crystals.

Indeed - I suspect that it would be done not by 'grinding', but rather by crushing, or pounding; followed by sieving, and then pounding the larger lumps further.

Flint will (normally) fracture conchcoidially (a trait it shares with glasses), and thus under a pounding it will leave fragments with sharp edges and corners. Grinding is likely to round over the corners and edges a bit, and thus leave a powder that is a less efficient abrasive. (Equally, rounded edges are sometimes better for polishing; but in context I don't think that'd be a major concern here).

It is also interesting is to consider what coarseness might have been used. I note (from a quick glance) that pore size in wood ranges from about 250 um (large pores in oak), to maybe 20 um (fine growth in pine). Therefore if the particles really did stick into the pores (as described, although I suspect the author probably _didn't_ take a microscope to an example), they would be somewhere in that range; which corresponds with F60 to F400, or thereabouts. I suspect the finer limit is more useful as a guide here.

If I was going to try something along those lines, I'd be tempted to try something around F320 or so to start with.

Mother nature grinds up a lot of stone for us. It's very common around the whole world, and known (in Derbyshire at least) as "sand".
I didn't think using it for sharpening was particularly unusual - I'm really surprised!
It can be stuck to paper to form a practical abrasive known as "sand-paper" (in Derbyshire at least).

Naturally occurring sand is a really poor abrasive. The corners are so rounded, it's got very little bite, requiring a lot of effort for very little return if used as an abrasive.

Indeed, Stalker and Parker, in "A Treatise of Japaning and Varnishing" (1688) caution against inferior papers made using sand, for this very reason.

 

[Jacob]

"....a stone of the flint species which is ground into fine crystals...."

Now there's a few simple words that covers a lot of labour. Flint isn't the easiest of materials to grind into anything, let alone fine crystals. I dare say an industrial process could be devised, but I suspect in this case, other, more labour intensive, methods were used.........

Mother nature grinds up a lot of stone for us. It's very common around the whole world, and known (in Derbyshire at least) as "sand".
I didn't think using it for sharpening was particularly unusual - I'm really surprised!
It can be stuck to paper to form a practical abrasive known as "sand-paper" (in Derbyshire at least).

Well - if you can find any flints ground into fine crystals by mother nature, good luck to you.

Millions of tons of the stuff on the south coast. Where you find flint you will find flint sand in the vicinity - rivers, beaches etc. I didn't realise this was a secret - we'd better get down there with buckets, before it's all gone!
NB strictly speaking not crystals but "crypto crystalline" which means crystal (ish). Quartz is harder.

 

[Jacob]

.
Naturally occurring sand is a really poor abrasive. The corners are so rounded, it's got very little bite, ..

Some is, some isn't. It depends what it's made of and how and where it was formed; beach, river, desert etc.
Mother nature also sifts and sorts it by size, in many circumstances.

 

[bugbear]

.
Naturally occurring sand is a really poor abrasive. The corners are so rounded, it's got very little bite, ..

Some is, some isn't. It depends what it's made of and how and where it was formed; beach, river, desert etc.

Sea(beach), river and wind(desert) all form sand by rolling. All such sand has round particles, and makes a poor abrasive.

Evidence and examples to the contrary welcomed.

If sand were suitable, I'm sure the Indian carpenters, being practical working folk, would have used it. They didn't.

BugBear

 

[sdjp]

.Naturally occurring sand is a really poor abrasive. The corners are so rounded, it's got very little bite, ..

Some is, some isn't

I'd be very interested in seeing an example cited of where naturally occurring loose sand is an effective abrasive.

NB strictly speaking not crystals but "crypto crystalline" which means crystal (ish). Quartz is harder.

cryptocrystaline means that the individual crystalline grains are so small that they can only be seen with polarising light in a microscope (or, obviously, more sophisticated equipment - but the term became definitional before electron microscopes). Prior to that discovery, they were considered glasses (hence the name; meaning 'hidden crystal') - behaviourally they are effectively glasses, not crystals (e.g. they exhibit negligible measurable anisotropy in hardness).

Fundmentally, flint and quartz are the same core substance, SiO2. On the Moh's scale of hardness, they both register a 7. Of course, that's not the most precise of scales, so I did some digging on that.

Lautridou et al, 'Proosity and frost susceptibility of flints and chalk: laboratory experiments, comparison of 'glacial' and 'periglacial' surface texture of flint materials, and field experiments' (1986) gives a Vickers hardness of 600 - 1200 for flints. (And, as you can infer from that title, they are not loathe to expound detail at length!).

S Middlemiss and R P King, 'Microscale fracture measurements with application to comminution', Int. J. Miner. Process 44-45 (1996) found for Karlsruhe quartz found a hardness ranging from .. wait for it … 600 - 1100 VHN.

So, er, no - quartz _isn't_ harder - they are, in general, the same. (On those numbers, flint looks harder - but I can find other, not precisely cited examples of 600-1200 VHN for 'quartz', so I'm unafraid to call that one a wash).

(I can't rule out one finding a _particular_ piece of quartz that is harder than a _particular_ piece of flint - indeed, given the ability to select crystal orientation of the quartz, that's positively expected to occur at some point. However, that doesn't change the general findings that they have the same hardness.)

 

[adrspach]

Late Henk Boss in his bood describes simillar sharpening utensils much closer to UK shores in continental Europe.
As medium why it has to be neturaly occuring? What is a problem with quarried material? As about grit size you can start with heat eroded gritstone and finish with different oxides such as chromiu oxide used for ages in green paint.

 

[Jacob]

Doesn't have to be naturally occurring. What I am saying is that using sand as an abrasive is wide spread ancient/modern technology not something "unusual" discovered by Indian carpenters. Sharper sands better (for most purposes). If you want a sharp sand grain one place to start would be a large grained natural sand which you could then break up in a pestle and mortar or similar - also a very ancient technology. Or the stone itself mauled with another stone etc
Ground or natural it's been in use from early times. Most "sandstone" (including stone types favoured for sharpening) is itself formed from natural sand.

 

[NickWelford]

:[/quote]And your Dad, and his dad, his dad's dad etc going back to the early stone age - several million years[/quote]

Well, a couple of generations anyway.....

 

[whiskywill]

Sea(beach), river and wind(desert) all form sand by rolling. All such sand has round particles, and makes a poor abrasive.

Water borne sand is a lot more abrasive than wind blown sand because of the dampening effect of the water when the sand is moved. It is possible to identify the origin of sandstone deposits by studying the grains to determine whether it was laid down in water or on land.

 

[goldspanner]

Whenever I see someone sharpening chisels or irons with side to side or figure 8 patterns, I always think it weird. This in comparison seems pretty normal!