My local fabric shop did not have an invisible zip (as per the notions list) so I purchased a normal one and made a lapped zipper closing for the gym slip - more in keeping with the '60s too - as invisible zips had not been invented. I'm sure I must have inserted a lapper zip before, maybe school domestic science classes, but memory needed jogging so I consulted the Vogue sewing bible. There was quite a bit of tacking (basting) involved but as always, preparation here saved time and mistakes later.
Thread trace the seam allowances - this included any taking in or letting out you intend to do for good fit. I've elaborated a wee bit on the directions for this technique because as always, sewing manuals leave out the little details.
1. Sew the back seam up to the tailor's mark (or the length of your zip) and secure with usual backstitching.
2. Fold over to the inside the left and right hand seam allowances, tack and press. You're working right hand side first here with the lap on the left.
3. Place zipper teeth a gnat's leg away from the folded edge. Tack securely.
4. With zipper foot and zip closed, sew through all thicknesses, as straight as you can, from the top. You need to move the zip pull out of the way at the top, then manoeuvre it back into place. At the bottom of the zip do not back stitch but leave a long thread.
6. Open and close the zip to make sure it works and you haven't inadvertently sewn over the teeth!
7. Assuming all is well with the right hand side - prepare to do the left. Close zip and gently manipulate the left hand fold over the right hand fold by about 3mm. Pin in place and tack.
8. Starting at the exact end of the right hand side, stitch across the bottom of the zip, pivot and up the left hand hand to the top. Sew as straight as possible - this is the stitching that the public will see. Again, do not back stitch at the start of sewing but leave a long thread that will be hand sewn through to the back and secured.
9. Check the zip works and the lapped side covers the zip when closed. If it doesn't, you need to rip out and re-do - no option I'm afraid.
10. Press gently to set the stitching and iron out any tiny wrinkles.
Finished outside view.
My invisible zips are never really that invisible so I like this method and will use it again. Normal zips are so much cheaper too. It is a neat way of inserting a zip and dare I say it - practically foolproof. If I can do it - anyone can!
Please note, I have not sewn shoulders or side seams yet on the gym slip, I was working only with the back of it. This made it so much easier to move around, sew and press, but you really need to check your fit first. I'd done my sway back alterations at the cutting stage and was content that any additional fitting could be made in the side seams later.
This is an inside view of the front - lots and lots of panels. The pattern instructions said to bind each raw edge with bias binding but I thought this would be too bulky especially with such a fine wool, added to which I was not keen to purchase 5 packets of bias, so I just H-stitched (the closest I have on my machine to an overlock stitch). It's a good way to use up all the odds and ends of thread and half wound bobbins. The dress is fully lined so this will never be seen.
Hope this helps some of you, especially if you are intending to make authentic 1960s frocks.
Thanks for reading. Ruth