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Medieval abrasives

Posted: Mon Aug 06, 2007 5:14 pm
by RottenCad
No, not the hessian underthings!

I'm trying to find out about rottenstone, pumice and sandstone use as abrasives for woodworking. I've got a couple of tenuous leads, but would be grateful if anyone already has any information they would care to share.

Many thanks,

Cad

Posted: Sat Sep 22, 2007 4:44 pm
by robin wood
I don't have clear evidence of abrasive use in woodworking before grinling gibbons in the 18th C. There is lots of evidence for lack of abrasive use, ie the majority of artefacts which today we would sand or plane such as wooden bowls and spoons, furniture parts and building timbers are left with a "tooled finish". That is to say finished with a clean cut with a sharp edge tool. A very small proportion of items including some of the fine medieval bowls called mazers have had the toolmarks removed. So far no surface analysis has been done to acertain what was used but I suspect scrapers rather than abrasives.

Posted: Sat Sep 22, 2007 6:06 pm
by chrisanson
dogfish skin( i think)

Posted: Sat Sep 22, 2007 11:43 pm
by Wilhelm
chrisanson wrote:dogfish skin( i think)
Yeh, i have heard that that was used almost as sand paper to smooth things down like bow staves and stuff

Posted: Sun Sep 23, 2007 10:01 am
by gregory23b
There is a type of grass, shave grass used to polish woodwork, mentioned by Theophilus, in conjunction with painting or preparing wood. But that is not what you require.

Posted: Sun Sep 23, 2007 3:08 pm
by robin wood
pretty sure theophilus' shave grass is horsetail, the same as used by grinling gibbons and japanes turners today. they use it fresh and green not dried, I am told it is equivalent to about 600 grit abrasive so just for final polishing after a cabinet scraper.

Posted: Sun Sep 23, 2007 9:03 pm
by gregory23b
Thanks for that Robin, I had wondered if it was a hard kind of sharp grass, akin to some pampas (but European in origin), other sources seem to concur with the horsetail, somethign that grows in abundance here in Suffolk. On emore item that is easier to acquire than it first appeared.

Posted: Thu Sep 27, 2007 12:19 pm
by Lord High Everything Esle
gregory23b wrote:Thanks for that Robin, I had wondered if it was a hard kind of sharp grass, akin to some pampas (but European in origin), other sources seem to concur with the horsetail, somethign that grows in abundance here in Suffolk. On emore item that is easier to acquire than it first appeared.
And it works very well indeed.

I can't see why they would not use a cabinet makers scraper. After all it is only the burred edge on a piece of metal. A curved one is very useful for taking scratches out of boxes!!

Tudor sources speak of fine English whetstones for use by barbers. "Leyland" I think.

Posted: Thu Sep 27, 2007 3:41 pm
by robin wood
"I can't see why they would not use a cabinet makers scraper. After all it is only the burred edge on a piece of metal. A curved one is very useful for taking scratches out of boxes!! "


Nor can I, its certainly technology that was available and it works well however I could show you many hundreds of images taken close up of worked wood surfaces and virtually all have tooled finish not scraped.

Posted: Thu Sep 27, 2007 4:00 pm
by Lord High Everything Esle
robin wood wrote:"I can't see why they would not use a cabinet makers scraper. After all it is only the burred edge on a piece of metal. A curved one is very useful for taking scratches out of boxes!! "


Nor can I, its certainly technology that was available and it works well however I could show you many hundreds of images taken close up of worked wood surfaces and virtually all have tooled finish not scraped.
Hi Robin
Thanks for clarifying that.

Are you saying there are no examples of smooth surfaces?

Posted: Thu Sep 27, 2007 4:36 pm
by robin wood
Well I like to think of the surfaces as a different sort of smooth. A skillfuly hewn beam for instance can be as cleanly cut as a planed one, just when you look at it with the light coming from the side you can see the facets. The barber surgeons canisters from the Mary Rose are very cleanly cut but not scraped or abraded. There are very few items I have seen where toolmarks have been removed and the only ones that come to mind are mazers.

Robin

ps I love the Quarles quote, how astute just goes to show just cos folks are long dead they were not stupid.

pps You say "and it works very well indeed" I would be interested to hear how you used it, green? dry? on what and how you would compare it to modern abrasive...similar to 600 grit?

Posted: Thu Sep 27, 2007 5:11 pm
by Lord High Everything Esle
robin wood wrote:Well I like to think of the surfaces as a different sort of smooth. A skillfuly hewn beam for instance can be as cleanly cut as a planed one, just when you look at it with the light coming from the side you can see the facets. The barber surgeons canisters from the Mary Rose are very cleanly cut but not scraped or abraded. There are very few items I have seen where toolmarks have been removed and the only ones that come to mind are mazers.
Hi Robin
Yes, I love the texture too. I suppose it depends on what the buyer was willing to pay. Utilitarian items need not be finished to the highest quality as long as they did their work efficiently.
robin wood wrote: pps You say "and it works very well indeed" I would be interested to hear how you used it, green? dry? on what and how you would compare it to modern abrasive...similar to 600 grit?
I use it dry for polishing jewellery. I have not done any experiments to measure the effectiveness though. I suppose I should but I don't make jewellery often enough.

Posted: Thu Sep 27, 2007 9:58 pm
by gregory23b
We know scrapers were used to smooth gesso work, Cennini, as well as specially made tools for mouldings.
A scraper provides a straight edge to profile, loose abrasives do not, hence the difference.

Posted: Tue Apr 15, 2008 12:41 pm
by Colin Middleton
When you look at the finish that can be obtained by a skilled carftsman, just by hewing and splitting, you can see why you wouldn't need a scraper. You put the extra finish onto things that you reall want SMOOTH, or where you want to show off, but for most purposes, the slight undulation of a good hewing job is problably enough.

We were at Smithhills Hall on Bolton a few years back and they were telling us that some of the boards had been replaced. All the visitors thought that the new boards were the originals, because the original boards were so wel finished!

Posted: Tue Apr 15, 2008 1:29 pm
by Mad Monk of Mitcham
Shavegrass (and bamboo) have a type of opal (the gemstone) in their fibres.

This is what you get the abrasive action from.

Traditionally in Burma and China, Jade was polished against bamboo.

Posted: Tue Apr 15, 2008 2:32 pm
by Jim
Well I reckon Emperor Sigismund was pretty bloody abrasive, if you ask me.



*gives a high five*

Posted: Tue Apr 15, 2008 3:38 pm
by sally
I've used horsetail on both wood and metal with good effect, the rough green parts of madder are also surprisingly effective for scouring rust off things. I ave a feeling I've seen a reference to this in connction with armour, but sadly have absolutely no idea where, or whether its period or modern in context.

Posted: Thu Apr 17, 2008 8:29 pm
by Gockee
I have heard of brick dust being used as an abrasive so tried it myself.

I tried some old brick bits ground up to a fine dust and mixed with (olive?) oil. When applied with a cloth it behaved like fine emery cloth. It worked very well at clearing up rust on knives left unused over winter.

Maybe this is like the 'rotten stone'?