I'm trying to make a bonnet to go with my blue bib-front dress. I made the mockup last Thursday, and I have made the brim of the final version. I took lots of pictures, to share my trial-and-error process.
First, the steps for the mockup: (Note I started from a commercial pattern for a "prairie bonnet.")
1) Trace the brim pattern on a stiff piece of paper, in this case, a file folder (this will be the "buckram" for the mockup). Draw the seam allowance along the brim and then trim it off.
2) Cut the brim out of a piece of muslin (including the seam allowance). Attach it to the file folder brim piece by folding the seam allowance over the file folder piece and securing it with masking tape.
3) Cut the caul part of the bonnet out of muslin. Turn up the bottom edge twice to make a casing. Sew the casing down.
4) Clip a hole in the casing through which the ties can be threaded.
5) Use some scrap string as the ties. Thread them through the hole and secure the ends of the ties at the other ends of the casing.
6) Gather up the caul to fit the brim and attach it with a running stitch.
7) Try it on!
Now, the final bonnet in progress:
1) Using your cardboard brim from your mockup (you either have to take the mockup apart or trace a new one with any modifications you made), trace your final brim on your buckram and cut it out.
2) Cut a length of millinery wire to go around the outside edge of the brim. Bend it to shape, and sew it to the edge with some buttonhole twist and a whipstitch.
3) Cover the brim with cotton flannel.
4) Cut out the outer (top side) covering of the brim from your fashion fabric and secure it to the brim with pins.
5) Set aside to finish later .....