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Converting regular patterns to bias

xyz123 | Posted in Patterns on

I have a dress pattern I like quite well but would like to make it on the bias.  What adjustments do I need to make in the pattern so it will fit as well as when made on straight grain?  Thanks for any help!

Linda

Replies

  1. starzoe | | #1

    Not all patterns will convert to bias and for a dress, you will need, with luck, double the amount of fabric. If a piece is cut on the fold, make a whole flat pattern. Usually all pieces are cut separately, nothing on a fold or on double fabric.To convert to bias, lengthen the "straight of the goods" line to the edges of the piece. I will quote from Adele Margolis' book Design your own dress patterns. You will first establish the crosswise grain "at the widest part of the pattern, place the right angle (90 deg) of your triangle directly over it, square the line across the entire width of the pattern." How to Establish the Bias grain: "with the triangle in the same position
    as for the horizontal grain draw the diagonal line opposite the 90 deg angle or square. This is a 45 degree angle."Sound complicated? In some ways it is, but it is a good exercise. I would try it first on a small item, like the front of a blouse in woven fabric. Your dress will not fit just by sewing the seams as they are shown, you would be well advised to make your seam allowances a whole inch.

    Edited 5/12/2008 4:11 pm ET by starzoe

  2. jjgg | | #2

    It's also best to have a center front and center back seam in bias dresses. The warp and weft threads (lengthwise and crosswise grain) have different amounts of stretch, with a center seam, you have this working for you by having the angles of the same grain going towards each other, YOu have to cut this out flat - single layer and lay the pieces out so they are angling in the correct position to get the best drape.

  3. User avater
    CostumerVal | | #3

    Fabric on the bias will get longer and skinnier.  You can use the knitters approach and cut a swatch 10"X10" and hang it by one corner for a day or two and then lay it flat and calculate the stretch lengthwise and shrinkage widthwise, then widen and shorten your pattern appropriately.  (I think Marcy Tilton just adds 4" to the width)  Or....you can sew your fabric into a long bias tube and wash and hang it that way, then the fabric has been prestretched for you.  Threads has published a few articles on this.  I'm not sure how to enter them into a posting.

    Val

    1. xyz123 | | #4

      That's a novel approach but if the stretch is all gone out of the fabric then it won't fit like a true bias dress will it?

      Linda

      1. User avater
        CostumerVal | | #5

        Actually, the hand of the fabric doesn't change, just the width of the pattern it's sewn into.  So the fabric will still move the same.  If you cut a bias dress with a grain designed pattern, your finished product will have stretched in length and there will be no ease to move in.  It's still not quite like a knit and shouldn't be skin tight as a knit can be.   The pattern needs to be widened or the fabric hung on the bias before cutting.  Most of the time bias designs are draped because you can see how the bias will hang on the figure before it's cut.  Not only that but every fabric has a different weave structure and that's going to effect how it moves and stretches/shrinks when hung on the bias.  By draping, you wont have to calculate the stretch and draft a new pattern each and every time.  The tubular method makes it possible to cut a predesigned pattern without having to drape or change the pattern.  You change the fabric instead.

        Have I totally confused you?

        O.K. just found the threads article,  it's issue 107, page 30 by Samina Mirza.  She advises that the "average" loss in width is about 30% and the stretched length is 35-40%.  She states that she still adds 1 1/2"-2" to the vertical seams, stay stitches all curved seams (necklines, armscye) and she hangs the cut dress overnight and then recuts if neccessary.  She gives the mathematical formula for calculating your tube width as:  fabric width in inches squared, times 2, then find the square root= tube circumference.  fabric width times original fabric length, divided by tube circumference = tube length.  She doesn't advise if this calculates flat sewn or hung and stretched.  I believe it's flat sewn because there's many more variables in hanging the yardage.  I think if you hung the yardage overnight and used a 1"-1 1/2" s.a. you would be fine.  As a matter of fact, I'm going to go do this today.  I've got some $1/yd fabric that the burn test reveals is not synthetic.  Hey you guys,  when I put a flame to this, the threads on the cut edge caught fire and held the flame, there was no beading or melting, all burnt fibers brushed away cleanly, and it smelled of burnt toast.  It has a wonderful drape and medium weave (plain)  What do you think it is?

        Edited 6/1/2008 9:06 am ET by CostumerVal

        1. User avater
          ThreadKoe | | #7

          It still may be synthetic. It could be rayon. Rayon is a wood fibre, and burns clean like a cotton fibre would.

        2. User avater
          Thimblefingers | | #8

          I'd say rayon, too. Rayon is classified as a "man-made" fibre as is it made from natural sources (not synthetic), usually wood fibre or sometimes cotton linters.

          1. User avater
            CostumerVal | | #9

            Thankyou.

            I had a rayon skirt awhile ago that had a similar drape and shrunk in the wash.  I've washed this once, I'll hit it again before I cut it.

            It ravels rather badly, but like I say, there were no beads formed on the end of the burnt threads so I don't believe that it is a synthetic blend either.  I'm toying with the idea of dye painting it.  I saw a presentation by Trish Stewart.  She colors the fabric with white crayola crayons and irons it in to seal the fuzz on the threads.  That keeps the inks/dyes from spreading into oblivion.  She said that if it spreads beyond your design lines hit it with a hot iron and it will stop immediately.  I'm way off subject now aren't I?  I'll start a new post after I give it a go.....after my current project, and the one after that....ect. ect. ect.

            Val

          2. User avater
            ThreadKoe | | #10

            Rayon is one of the "natural" synthetics that is between a natural fibre like cotton or silk and a synthetic like polyester or nylon. It can take dyes and surface treatments such as the crayola or batik like you were talking about. Treat it like a washable silk and you will be fine. I like using it because it has buttery feel to it, and is cooler to wear as it does breathe.

            Edited 6/4/2008 10:43 am ET by ThreadKoe

      2. User avater
        CostumerVal | | #6

        O.K.  found an even better one: issue 104 the fitting column by Karen Howland.  She lays her fabric out and squares it up.  Then "fold each corner to the opposite selvage and mark the intersection with a pin; then measure the true bias diagonal.

        Hang the fabric from one corner overnight to stretch and compress bias directions, then remeasure the horizontal and vertical diagonals.  Find the differences between each diagonal's hung measure and its original flat length.  Divide the hung fabric diagonal by the difference; this is the width/length factor.  Divide each pattern piece vertically/horizontally at intervals equal to the factor and spread/overlap at each division by 1". (slash and spread your pattern)  Then add 2-3" to the side seams. 

        So, if the stretched/shrunk length divided by the flat length is 6; then you slash your pattern every 6 inches and spread or overlap 1" at every slash.

        Convert all darts to ease, move pants darts to the nearest seam, and increase seam allowance.

        Val

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