Dress zips in Dresses and Gowns.
Normal insertion of a dress zip is bulky. However some designers have started to insert zips resting them on the top, which can look very fashionable. To be honest I don't like putting dress zips in dresses in the traditional way. They are okay in trousers, but I always convert to an invisible zip when I have an alteration such as taking in when there is a dress zip or replacing a dress zip with an invisible zip. You might ask "why would I do that?" The reason is because the flap that folds over the dress zip sticks out even when it has been ironed flat. Usually the zip is in the side or back and this means the small flap adds more bulk to the body. Also as the garment gets older the fabric tends to fade or get worn in sections around the flap, particularly at the top.
Zips areas can give more room, particularly from a dress zip converted to invisible.
Letting out - With a dress zip if the garment is too tight, the stitching will get pulled on the outer fabric, which means you want to fix the problem before it gets to this stage. If you come across this problem where the weave of the fabric has opened, try laying it on the ironing board (once the zip has been taken out) and give the area a light iron just to warm it up. Use your finger nail to ease the weave back together. Work from the top down to the bottom. I have on occasion used the end of my nippers or the end of tweezers to ease it in. It depends on the fabric. There is a lot of fabric used in a dress zip so by taking this zip out, ironing the fabric flat, then inserting an invisible zip you will usually get an additional 2.5 cm or (1 in).
Taking in - When taking in the sides is not an option on a garment, take a look at the zip in the centre back. Pin the centre back even though there is a zip. When a garment is made the panels are laid on the fabric ensuring that the centre back would be on the straight of the grain. A dress zip will lay reasonably flat on the straight of the grain, but if you are taking in at the zip area, then fabric will more than likely be off the grain. That means some bias will be involved. If you put a dress zip back in, there will be a twist in the flap over. An invisible zip WILL NOT have any twist in the fabric. And it sits very flat against the body.
If you have to put a dress zip in and the garment is lined, attach the zip to the lining first. Bagging the top of a dress zip is more time consuming than it is bagging an invisible zip. If I have to put one in, the last thing I do is topstitch around the zip. I prefer to attach the fabric to the zipper first, making sure it is sitting at the same position at the top and bottom.
If the garment is lined, I would attach the zip to the lining first. Then do the outer.
Happy altering
Judith aka genie