Full Chisel Blog

July 22, 2009

Variable Grit Abrasive

I really can’t call this a variable grit sandpaper because it is not sand and it is not paper, but it is similar.  It can be used as a burnisher in its polished condition and it can be altered into other grits by abrading it with equivalent abrasives.

I selected a piece of quartersawn white oak (Quercus alba) and cut it to a size that was comfortable in my hand,  2 1/8″ by 4 1/2″ by 1″ thick.  The wood will be stable even if I use it wet or dry. 

variable grit1

I cut the piece of sting ray skin (shagreen) to the size of the oak block with a wax pencils width larger than the block.  I then used large shears to cut out the material.  This stuff is tough, the little tubercules of mineral deposits are very hard.

Variable grit2

I allowed the glue to dry, I used liquid hide glue and just kept working it flat and smooth over about a 30 minute period every several minutes to make sure it made good adhesion.  I put a bit of glycerin in the hide glue to keep it flexible as there may be some small movement.  I will also treat the edges with a mixture of distilled water and alum to make the edges waterproof.  For a complete discussion of making Hide Glue waterproof see Hide Glue – Historical & Practical Applications.

After about 20 minutes work with sharp shears and mostly a coarse file I was able to shape the abrasive block (sanding block) so that the sting ray skin was even with the edges of the block and smoothed to a burnish finish.

Variable grit3

I can use sandpaper to make this abrasive block any grit I want and the grit will correspond roughly to the grit of paper I use.  Because these mineral deposits are so hard they will hold their edge for quite some time.  This is an old material and technique that I find fascinating.

Stephen

5 Comments »

  1. I’m curious as to which ocean in Utah has a stingray population?

    Comment by Gary Roberts — July 22, 2009 @ 1:45 pm

  2. Gary,

    Haven’t you seen the 1776 map by Pacheco for the Dominguez/Escalante Expedition? Clearly shows a connection between the Salt Lake and the Pacific Ocean.

    Stephen

    Comment by Stephen Shepherd — July 22, 2009 @ 2:25 pm

  3. […] Shagreen is a bit of a loose term for a range of rough-textured skins. The 17th century Persians made it by pressing pebbles or seeds into horse, camel, or donkey skin to give them a bumpy grain; since then it has been used for a variety of coarse-grained skins. Now it most frequently refers to the skins of rays as well as (less frequently) sharks, dogfish, and other cartilaginous fish. These are covered in protrusions called placoid scales; they’re very similar to teeth, with an inner core of pulp surrounded by dentine-like material and a thinner layer of enamel. In Japan shagreen was used (undyed) for sword handles and armor, and in China for bows, in both instances its texture offered the user a better grip. In Europe for a long time it was simply an inexpensive byproduct of the fishing industry, used for abrasive: check out the description of making this modern shagreen sanding block. […]

    Pingback by Shagreen « Current Projects — March 24, 2012 @ 5:04 am

  4. Hi Stephen,

    Forgive me if I overlooked a reference you may have made, but I was wondering where you got the skin you used in this tutorial. I am attempting to put together an ongoing 18th century woodworking demonstration of sorts and I would very much like to include this. If you could point mien the direction of a source for these skins, it would be very much appreciated.

    Comment by Brian — November 25, 2013 @ 11:38 pm

  5. Brian,
    I bought the skin from Tandy Leather Company here in Salt Lake. They only had them for a short while.

    Stephen

    Comment by Stephen Shepherd — November 26, 2013 @ 8:21 am

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