Notes on designing curtains with rings

This is a post where I point out things to future Alice which should have been obvious to past Alice when she bought curtain fabric for her spare room.

For context, I am making curtains with 40mm metal eyelets at the top.  I need metal eyelets because I am interlining with blackout fabric, and making a polycotton lining too, plus buckram.  This is quite a thickness to expect shonky plastic rings to withstand.  Therefore, I purchased some badass tools to insert metal eyelets from Hanolex.  It involves the biggest hammer I may ever own.  The break even point in tool investment seems to be when you are making more than one set of eyelet curtains, especially when you take into account the recorded delivery postage in sending your beautifully handmade curtains off to someone else to butcher in the eyelets for you.

I like to use the blackout as an interlining rather than a lining fabric.  When making curtains, one tends not to take the lining all the way to the curtain edge.  I find the blackout fabric to be quite stiff compared to some fashion fabrics used for the front of the curtain, so when using it as a simple lining, you end up with floppy leading edges.  I've even seen this done on sample curtains in a well-to-do posh national chain of stores.  Eugh!  Therefore, I like to use the blackout as an interlining, cut to the finished curtain size and tacked inside, making all the curtain the same stiffness.  I then use a thin cotton or polycotton to line the curtain.

Designing your curtain

Here follow some complicated trade-offs and calculations that I won't repeat here, but consider the following constraints:

1. For a pair of curtains, each curtain needs to be at least twice the width of the window area it has to cover.  E.g. for a 2m wide window with a pair of curtains, each curtain needs to be 2m wide or more.
2. You need an even number of rings, and Mr Google suggests typical spacings for 40mm rings are 16-18cm.  The spacing you choose is to some extent determined by how far your curtain pole stands off the wall, which should be just a little more than half your ring spacing.  Clearly if you have M rings, your total curtain width will need to be M x ring spacing.  This allows you a bit of leeway to play around with the number of rings, the ring spacing and the total curtain width, subject to the next constraint.
3. Typical fabric widths might be 140mm, so you may need several drops of fabric in order to get your total curtain width.  Consider where the join should be between two drops: it ought to fall in a furrow between two rings, i.e. with an even number of rings each side of it.  Make sure your ring spacing and number of rings allows you to get this seam positioned correctly, bearing in mind the width of your fabric (which is fixed).  It's not as easy as you'd think.
4. With all of the above, make sure you're allowing for turnings at the edges on the front fabric!  On top of the finished curtain size, I allow 5" at the top, 3.5" at the bottom, and 2.5" at each side.  I allow a 1/2" seam to join drops.

Having solved that headache, you might want to consider where you place the seams between drops of blackout interlining and polycotton lining.  I didn't want a stiff section in my curtain, so I plan to stagger the seams.  Since it's the next stiffest fabric, I'll place the join in the blackout lining in a different furrow from the front fabric (with an even number of rings each side).  The polycotton lining is relatively thin and floppy, and in any case is on the reverse, so I'll place the join mid-way between that of the front fabric and blackout, even though this is on a projecting fold.

The narrowest drop of front fabric probably looks best toward the outer edge of your window on each curtain.

For lining, I plan for it to appear on the reverse of the curtain as a neat rectangle coming 4.5" down from the top, 2" in on each side, and 2" up from the bottom.  I allow 1/2" for turning on the top and sides, but 2.5" for creating a deep 2" machined hem along the bottom.

I will use 5" buckram along the top edge for stiffening, and I expect to place my eyelets with their midpoints 2.25" from the top of the curtain.  The outer two eyelets are spaced by half the eyelet spacing from the curtain edges.

Matching obvious patterns

I should have unrolled several meters of the fabric from the roll and stood well back before buying.  What I thought was a lovely swirly pattern turns out to have VERY obvious repeats which really ought to be matched.  What is more, my guestimate of yardage in the shop was pretty good at first sight: I bought 6.5m, and my later calculations show I need four drops of 62" each, which is 6.3m with no pattern matching.  Clearly this is very frugal of me, but I am now cursing myself for not allowing enough for pattern matching.

When you are standing in the shop with a winging toddler, how much extra fabric should you buy for pattern matching?  Turns out to be quite simple.  Firstly, measure the vertical pattern repeat.  Then buy enough for the number of drops (N), plus N times the pattern repeat.  So for my fabric, I should have bought 4 x 62", plus 4 x 24" (because 24" is the enormous pattern repeat distance).  So I ought to have purchased just over 8.8m to be safe.  That's quite a difference from the 6.3m!  I now need to attempt to buy another 2.2m+ of the same fabric, six months after my original purchase, if they still have it.  ARGH.