Having successfully finished the fronts of the trousers, it’s time to turn attention to the backs.
First thing I need to do is put some reinforcing interface around the areas that will be sewn. These are around the back pockets and a small fitting dart that goes between the pockets and the waistband.
Looking closely at the GAP trousers I find they did this in one piece, so I copy the shape and cut my interface in a similar way (see right). Because the interface does not cover the entire area of the fabric I am stiffening, the edges are cut with pinking shears to avoid a line being visible from the right-side of the finished trousers.
I then iron the interfacing in place and sew the darts (see above left). I don’t bother to trim the seam allowance of the darts because they are so small and it may only weaken the trousers. I press the darts flat from the right-side (see above right).
I am now ready to do the back welted pockets. Setting welted pockets like these has become a regular thing for me, but this time I need pay a little more attention to detail; the welts are a little finer; the pinstripes means cutting needs to be more precise; and because the trousers are not fully lined, the pocket bags will be exposed and will need to be much neater and have no exposed raw edges.
I have extensively covered welted pockets before when I was making my Calico Tennant Coat, the Alcantara Tennant Coat and Six Trousers, so I will skim over a few things and try to focus on only the unique aspects of these pockets in this entry.
The pieces I prepare are two interfaced welts, folded and pressed in half; one interfaced pocket facing; and a button loop made from pinstripe fabric (see left). I have carefully cut and pressed these so pinstripes will be visible on each.
I then mark the position of the pocket (see below left) and sew the welts on the right-side, flipped upside-down (see below right).
I then cut between the two welts (see above left) and snip to the ends of the stitching in a Y shape at each end (see above right).
The welts are then finished (see right, 1).
I can then turn the upper welt round to the back (see right, 2) as well as the lower welt (see right, 3).
I then press firmly to get everything looking sharp (see right, 4).
Note that on both welts I have a single pinstripe visible. If I had let the welt fall between pinstripes, it would appear to be plain brown fabric and look a little odd.
I can then pin the button loop in place under the upper welt (see right, 5). Again I have arranged it so a single pinstripe runs along the centre of the loop.
I then sew the facing of the pocket, which will be seen inside the back of the pocket, to the upper welt.
Sandwiched between them is the button loop (see left).
I sew along the existing stitchline that secured the welt in place.
The next thing to do is the pocket bag, which is a lot more challenging than normal. I want to do it so there are no exposed raw edges that could fray, but I also don’t want to over sew the edge of the pockets too much so they show through to the outside and are uncomfortable to wear. The pocket bags also needs to extend up to the waist band so they are supported, rather than just hang from the pocket as I have conventionally done in the Tennant Coats.
It is quite complicated to explain how the bag works, but I think the easiest way is to describe the path the fabric follows to form the bag. This will give an overview of what I am trying to achieve.
It starts at the waistband then hangs down on the outside of the pocket and is attached to the lowest part of the pocket facing as it passes; it then continues down to form the pocket before folding back up to complete the bag; it is then sewn to the bottom of the lower welt as it comes up; a long horizontal slit in the fabric then allows it to go past the pocket opening and return to the waistband to match the start of the bag, both of which are later secured when the waistband is sewn.
So, following that, the first thing I do is to fold and press the edges of the welt and pocket facing that will be sewn to the bag as they will be top-stitched rather than seamed (see left). You can see the 5mm or so I have turned up, like a tick.
I then lay the length of pocket bag material over the trouser backs, allowing a little extra at the top and pin it where it lays over the pocket facing. I then top-stitch the two together (see right).
I then fold the pocket bag to length and chalk mark the level of the pocket opening on the return. I further chalk mark for the opening I need to cut to allow the pocket bag to pass by the pocket opening (see below, top left). I then cut the slit I need, in a similar way to when I cut before turning welts, with a Y shape at each end (see below, top right).
I then sew the bottom of the lower welt to the returning pocket bag (see above, bottom left) and pass the entire trouser back through the hole and the pocket bag is now in its final position (see above, bottom right).
I then turn the edges of the slit inside out and am able to carefully sew them around the inside of the pocket opening.
Finally, I need to neatly seam the vertical sides of the pocket bag. Ideally I would like to French seam them, but it is not possible to sew it one way, then turn it right-side. What I do instead is simply fold the edges in on themselves and at the welts fold them between the welts (see above left). I then top-stitch the sides to close the pockets up (see above right).
All I need to do is sew a button for the loop to secure around and the back pockets are finished (see below).
Here you can see into the pocket to the pocket facing (see below).