I thought I knew how best to sew a curved hem but hey, there are more ways than I realised. The aim is to fold up the longer raw edge (i.e. longer than the stitching line) and sew the hem without getting puckers, wrinkles or pleats.
I found this YouTube video by Prof PIncushion (Link here) showing three different methods.
I very much recommend the suggested machine-basted stitching line (that's the one with the really long stitch length) because it makes pressing over the seam allowance a lot easier. You will get a more even distance from the fabric edge to the fold line that will look a lot better than eye-balling while pressing. It is such a pain when you have to repeat ironing after a first attempt looks frustratingly wobbly. Folding the fabric over at the basted line is easier because of the perforations in the fabric: it's almost as if the fabric wants to fold along that line. Highly recommended.
When you work with a thickish wool fabric then a high iron temperature and plenty of steam will shrink the fabric a bit so you can get the raw edge to reduce to the smaller measurement. That's what I did: baste, fold over and press and then press and shrink. But you can't do that with all fabric fibres. You need a different method for other fabrics.
I would be inclined to go with the first method Professor Pincushion shows but baste two lines: one as she describes, and a second one for where I want to fold the fabric over. This saves on the time it takes to measure and mark the fabric as per her demonstration. The bit I learnt from this video is her tip to pull at the higher up basting stitch line in those places where your fabric won't lie flat enough - to ease it in. That's really useful!
The rolled hem also sounds useful but to be honest I wouldn't have the patience for trimming the seam allowance as shown. Instead I prefer baby hems, particularly with light-weight fabric. This works best if you can overlock (serge) the raw edge. I machine baste at a folding line at a distance of about a centimeter away from the edge, and then overlock the raw edge. Then I press the fabric over once. I then edge-stitch the hem two centimeter from the folded edge. This leaves a very narrow seam allowance and keeps the hem nice and drapey. This can be lovely for the hems of flutter sleeves. A edge that's been folded over twice could be too stiff.
I also like the third method of sewing a ribbon to the hem, either on the right side as a decorative feature or on the inside. Either would give a skirt hem a nice bit of weight. A variation of this method is to sew on a ribbon onto the outside to diguise your top stitching. Ribbon or braid can be placed at the edge or even a bit higher up for a very attractive feature. You may want to use the same ribbon or braid elsewhere in the garment to tie it all together.
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And here is another YouTube video by JOANN Fabric and Craft Stores (Link here).
I really like the look of the rolled hem. This method will probably strike you as needing too many basting lines that you need to pull out at the end - but just look at the neat result! I think this makes it well worth it.
The bias facing method is also really impressive. It takes a bit of trial and error to figure out how much to pull at the bias strip to get it to the right tension. I would be tempted to pull a lot less than the word 'pull' suggests - just lay down the strip and smooth it to lie flat along the middle of the strip length (where you'll sew) as opposed to at the very edge. It is a touch annoying that you have to trim this down, but the sewn edge makes for a useful guide. I'm all for top stitching this instead of hand-sewing a blind hem. On the other hand, a thicker wool type fabric is quite forgiving and easier to hand sew, giving a really beautiful result.
The bias binding method takes more preparation for pressing the bias tape as described. The technique that I found handy involves a darning needle stuck into your sewing board cover at both its ends, as a "gate" to pull the flat tape through and press. This preparation will make sewing the strip onto the hem a lot easier. The suggested stitch-in-the-ditch method takes quite a bit of practise (you can also see how slowly she stitches). I must say that I am not hugely fond of the look you achieve with this method, I prefer a ribbon over binding or the above bias facing that will put the bias strip onto the inner side, making it invisible. I find that this looks a lot more grown-up, the binding method reminds me of kids clothes, but that's just me.
So there you have it! Six different methods (seven if you count my baby hem method that I snuck in there), something to try out when you're not happy with another method. You'll find that the fibre and the weight of your fabric will make some of these methods more useful than another. Go and experiment!
If you are very new to sewing and find all these rather overwhelming then I recommend the first method Prof Pincushion describes (just with two basting lines). Or baby hems when you have an overlocker stitch available and need a really drapey hem for a thin fabric.