Subject: curling hammered brass prob.

From: [email-masked] (Toby Rockwell)
Date: 23 Oct 1994 18:26:22 -0400

I need to produce a 4 by 5 1/2 inch square piece of .040 leaded yellow 
brass that is flat with a hammered surface.

No matter what pattern I have tried hammering 
it in, the piece develops a curl due to the elongation of the brass in 
both length and width.  This causes a springy curl to the metal so if the 
curve is straightened in the x direction it is worsened in the y axis.  
Is there a technique I can use to avoid this?

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*  Toby Rockwell                 |      [email-masked]        *
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From: [email-masked] (Steve Hampson)
Date: 24 Oct 1994 18:58:24 GMT

> Is there a technique I can use to avoid this?

It sounds like you are talking about a process called planishing.  For
a flat surface you need a mirror polished hammer with a slight curve on
the surface.  The curve is about a 3 foot radius.  A flat hammer is
used for convex surfaces.  You also need a polished "stake" that will
support the work at the point of contact.  For this piece you could use
the flat surface of an anvil.

I sounds like you are hitting the work too hard or using a hammer with
too much curve.  For example, try hitting a piece of scrap with the
"flat" side of a ball pein hammer, and compare that to effect of the
pein.  

When planishing is done correctly in several passes, the result is a
very smooth, clean surface.  If you stop after the first pass, the
result is a very pleasing surface with a subtle texture of small (1/4"
perhaps) circular depressions.  It sounds like this is what you want.

You must anneal the brass before you start, if it is not soft and
possibly during the process.   The surface will oxidize when it is
heated and must be cleaned with an acid.

I have a very good book on silversmithing which describes this process.
 I'll look up the title if there is interest.

Steve Hampson                           
Blue Sky Research
534 SW 3rd Ave
Portland, OR 97204
503-222-9571
503-222-1643 fax