I just finished a test on one of my few remaining scrap pieces, and am pleased. I have found the right thread for this project! Other than forgetting to trim the edge on the french seam, this one came out pretty much perfect:
|Sulky rayon thread on silk charmeuse|
While exploring Hancock's thread section, I discovered the problem with the Gutterman cotton thread: I bought the wrong kind by accident. In our local Hancock, the 200m spools are handquilting thread. The 100m and 800m spools are for machine use ... strange. But it does explain the stiffness in the seams. I have moved this spool and what remains on the bobbin here to my desk where I do all hand sewing. The Gutterman machine cotton thread looked like it would probably work, but it didn't have the shine that the rayon thread does. "Shiny for the win!" as my hubby and son would say.
NOW I am finally ready to put this blouse together ...