Underlining and Hong Kong seam finishing in one

I promised some time ago that the next time I'll be making an underlined garment, I'll take pictures and try to describe the process.

Recapping things said previously:

• I'm very partial to underlining lately, I think I said it before on my blog, I like how the underlining moves with the fashion fabric, instead of having two separate garments joined at some seam, like in the case of lining. It is a subjective things, of course, but I'm going to use underlining instead of lining for most of my projects
• Part of my great liking of underlinings is this gorgeous knit lining (nylon sheer, sold in many online stores as bra cup lining; my beautiful friend Marji also recommends using Powerdry - which I don't know but from what I read about it, it is marvelous because it keeps your skin dry when you're sweating) that I'm using - it is stretchy, thin, it does not alter significantly the drape of pants and anyway it improves it, and it has a silky side that feels absolutely luxurious against the skin. Plus it really minimizes the wrinkling which is very important, taking into account that I spend long working days sitting at a desk.
• IMPORTANT: I buy this nylon sheer locally and none of the stores sells online. But by looking at pictures on the Elingeria website, I think this nylon sheer is what I use.
  

Technical details:

I've used this tip on PR for underlining and giving a Hong Kong finish to the seams at the same time. I'd like to explain a bit this method, insisting on the turn of cloth. This method has you cutting the underlining fabric with a supplementary seam allowance of 5/8 (aprox. 1.6 cm) . Therefore the fashion fabric has a 5/8 (1.6 cm) seam allowance and the underlining fabric 5/8 x 2 = 1 1/4 (aprox. 3.2 cm). You then join the fashion fabric wrong side to the underlining wrong side with a 1/4 seam allowance. I must stress that it is very important: 1) to be able to cut accurate seam allowances (I use my rotary cutter and its guide arm); 2) to be able to sew accurate 1/4 seams - use your 1/4 foot if you have one, your zipper foot (mine sews an exact 1/4 seam allowance if I align its edge to the fabric edge). I use my normal foot and a special setting on my machine which allows me to sew an 1/4 straight stitch seam. Now, from the supplementary 5/8 (1.6 cm) seam allowance, 1/4 is caught in the seam (0.6 cm), another 1/4 (0.6 cm) wraps over this 1/4 seam creating the Hong Kong finish and the remaining 1/8 (aprox. 0.3-0.4 cm) is for the turn of cloth. Now, if your fabric is especially thick or thin, you should increase/decrease the turn of cloth and the respective supplementary seam allowance of the underlining fabric. For a thick fabric, you'd cut more than 5/8 supplementary allowance, for a thin fabric, less.

My fabric for this project is a medium weight one, therefore I used 1" (approx. 2.5 cm) supplementary seam allowance on the underlining.

1) Cut your fashion fabric with "normal" seam allowances. Cut your underlining with another 1" seam allowances, or a bit less or a bit more (see above). I use my rotary cutter and its arm to cut accurate seam allowances. This is very important. See here the difference between the two pieces.




Warning: you only add the 1" supplement to vertical seams! The horizontal seams can be finished either using the method described by Shannon in this post, or by simply serging them, treating the fashion fabric and the underlining as one. Teaser pic... see how I serged the horizontal seams on my dress and then applied a ribbon, not to act as a waist stay (this dress doesn't need one), but just to make the seams look more beautiful.



2) Sew the darts in both the fashion fabric and the underlining. Most of the time I press the fashion fabric darts towards the center of the garment and the underlining darts in the opposite direction, to minimize bulk:



For my current project, there are quite large darts at the bust. I decided to slash and press open both the darts on the fashion fabric and on the underlining (only for the top part, the skirt, as you can see above, has the darts pressed in opposite directions):



3) Now, with the right sides together, sew all the vertical seams with a 1/4" (approx. 0.6 cm) seam allowance. I have an 1/4 foot now that makes this job easy. Before, I used my zigzag foot and adjusted the needle position or my zipper foot.



4) Open your seam allowances, then press them towards the underlining.



5) Wrap the underlining over the seam allowances, creating a Hong Kong finish.



6) Press in place and sew in the ditch. Ta-daaa, you're done!

Here's how it looks on the right side:




And the wrong side: