This is my method, there are many variations on muslin-making but here’s what I did. (You wanted to see the process – you got it!)
Depending on the style of the dress, you may only need to muslin the bodice. In this case, I didn’t want to waste yards of muslin on a gathered skirt, knowing it would definitely fit over my hips. So, I planned to muslin the bodice only.
You might want to muslin a whole dress – sometimes the weight of the skirt will affect the way the bodice fits! It will also give you a better idea of the finished dress’s look and feel. But I already like the way the dress looks so I’m going to just focus on the bodice for fit.
First, locate the bodice pieces only. No need to cut muslins for facings or detailed pieces unless they’re required to get the fit accurate. Cut the sleeve if the dress has sleeves. Pin your pattern pieces to the muslin.
Then, mark any darts, pleats or other internal markings. I like to write with pen (because I can!) Write the pattern name and number on the muslin piece (Simplicity 3965), as well as a description of the pattern piece (Bodice Back).
Next, machine baste along the seamlines, tracing out all edges and any darts. (I’m sewing along the pen lines of the darts.)
Why am I doing this? So sewing the muslin can be like sewing with the tissue pattern pieces – everything is marked and labelled, and the seamlines are super clear for accuracy. Any changes I made will be easy to apply to the pattern pieces this way!
Run your stitching off the edges of the fabric, don’t pivot at the corners.
Now, make all of the darts, pleats or tucks in the bodice. This should be easier than normal because you’ve stitched the pleat/tuck/dart lines with machine stitching. Press the darts towards the centre or down, as you would on the real bodice.
Figure out where the closure is going to be. In my case, it’s a centre back zipper. So I will sew the shoulder seams and then the sideseams, leaving the seam with the closure open.
Next, take a zipper (any zipper!) and pin along the closure opening. In my case the zipper will be way longer than the opening, but that’s OK. I’ll sew along the bodice back seamline and leave the rest of the zipper hanging.
Clip curves along garment edges, and fold in your seam allowances.
This will give you a better idea of where the neckline will sit, and where the outer edges of your dress will be. (I tried on the muslin first, without clipping the edges and could barely get my arms through the tiny armholes!)
Time to try on the bodice! Wear the bra you’d wear with the finished dress. Siince I’m small-chested, I have a vast assortment of padded bras. If I fit with my least-padded bra, it will fit completely differently than my most-pumped-up bra. If you prefer vintage-style bras, then fit your muslin wearing the correct bra.
Next up – fitting the bodice and correcting the pattern!