Shay Pendray's Stitching Toward Perfection
This is a small booklet full of techniques for good embroidery. It is a wonderful resource that explains how to use your laying tool exceptionally well. (The more recent Shay Pendray's Inventive Needlework repeats the laying tool information and is probably easier to find, but note that Stitching Toward Perfection has better information about the use of flat silk.)
Shuji Tamura's Techniques of Japanese Embroidery explains everything you need to know about Japanese emboirdery, from how to lace your frame to how to twist flat silk to make it up for embroidery. Japanese embroiders make up their flat silk into various sizes for various stitches, depending on the technique they want to use. It is a wonderful book for anyone who is curious about this ancient art and is a great reference tool for folks like me who plan to explore some of the techniques.
Since you may not have either book handy, I've found information about flat silk for you to look over. First, Carol Anne's Japanese Embroidery blog has a lovely posting about Japanese flat silk. She shows you the various sizes (twists) of Japanese silk before and after they are stitched.
http://threadsacrosstheweb.
Here is a color card of the various flat silks available from the Japanese Embroidery Center in Atlanta.
http://www.jecstore.com/Flat-Silk-OFS.php
You can also order from Australia. Thread Studio has a lovely photo of the various colors available.
http://www.thethreadstudio.
Kay Stanis's beautiful website has tips for laying flat silk. Believe me, I studied this very carefully!
http://www.the-gilded-edge.
You can buy flat silk from her, too
http://www.the-gilded-edge.
Jane/Chilly Hollow
Main blog at http://blog.360.yahoo.com/chillyhollow