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How to Widen a Slot-Seam Opening

Threads contributing editor Mary Ray demonstrates some creative ways to use slot seams as surface design in “Variations on a Seam,” Threads #168 (August/September 2013). Here, she shares a neat method for widening slot-seam openings to uncover the underlay. Follow these steps to learn how to turn this otherwise basic construction element into a unique and unexpected embellishment.

How to widen slot-seam openings to show off an interesting underlay fabric:

Prepare the slot-seam opening by adding 1/8 inch to the pattern's seam allowance width.

1. Prepare the slot-seam opening by adding 1/8 inch to the pattern’s seam allowance width. Fuse interfacing strips to the seam allowances’ wrong sides. Baste along the seamline, right sides together. Then press the seam allowances open. Cut an underlay strip 3⁄4 inch wider than the pressed-open seam allowances.

Center the underlay strip, right side down, over the seam allowances (aligning the raw edges), and pin.

2. Center the underlay strip, right side down, over the seam allowances (aligning the raw edges), and pin. The strip will bubble away from the basted seam because of its additional width. Topstitch from the right side 3/8-inch from the basted seamline (shown), taking care not to catch the underlay strip’s excess material in the stitches. Repeat on the remaining seam allowance (shown pinned).click to enlarge

Remove the slot seam basting stitches from the right side.

3. Remove the slot seam basting stitches from the right side. Encourage the folded edges to spread apart, and press from the right side. The photo shows the widened slot seam complete.

Have you used slot seams as surface design in any of your garments? What other basic construction elements have you used as embellishments?



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  1. DLZD | | #1

    I've been sewing for 50 years and have never heard of a slot seam. How and/or where would one use this technique?

  2. seniorslugger | | #2
  3. User avater
    eatsallinsects | | #3

    I LOVE slot seams but haven't sewn any in probably 60 years!
    THANKS for the reminder of how wonderful they look!

  4. seniorslugger | | #4

    Me too, have sewed for ions and have never heard of slot seams. Would like to know though

  5. Sigrid | | #5

    Lovely technique to enhance the effect of a slot seam. Think it is important to note that if you do this on pattern pieces already cut, you widen you pattern piece with the 1/4 inch with this. Especially important if you have multiple slot seams.

  6. User avater
    sewold | | #6

    I've never used a slot seam either but it would be a good technique for an accent. If you have already cut out the garment and didn't cut extra, why not just sew closer to the original seam line? An edge stitch wouldn't detract from the accent fabric.

  7. User avater
    sewold | | #7

    Just had another thought - this would be a good way to add just a little ease when a garment is feeling a little too snug (weight gain, maybe?).

  8. vintagenonnie | | #8

    I'm with you DLZD, what is a slot seam!?! I too have been sewing for many years & have never encountered anything by this name.

  9. User avater
    Countessa | | #9

    Slot seams are fun to use. They basically give a glimpse of a contracting fabric under the seam. Looks great when a 'flashy' material is used as the contrast; livens up an otherwise plain outfit. This is a good example: http://www.sewastraightline.com/2010/01/slot-seam.html
    Works best on straight seams. Have fun.

  10. User avater
    shaunpollock | | #10

    this is awesome stuff

  11. User avater
    GracefulSewing | | #11

    I learned about slot seams in Katrina Walker's Craftsy class.(Mary Ray's explanation are great, but several of you are asking what they are so maybe this will help.) A slot seam is a design element used to break up a solid color by exposing a ¼"-¾" strip of contrast fabric between seam edges. The original seam is basted closed and the seam allowances are interfaced and pressed open. Cut your contrast strips to equal your total seam allowances plus the amount of contrast you wish to expose. (For instance, 1¼" + ½" = 1¾" strip yielding a ½" slot.) Using a standard stitch length (not basting) seam the contrast piece to the raw edges of the original seams, keeping excess fabric free. Remove the original seam basting and gently spread it open to expose the contrast. Press the new seam area flat and topstitch each edge of the original seam allowance to support and highlight the contrast fabric. If your pattern fits perfectly, you will need to adjust the panels on either side of the contrast by ½ of the total exposed amount. As some sewers mentioned, this could also provide a little extra room for a garment that is a little too tight.

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