Tips for Sewing on the Bias

Tips for sewing on the bias, bias cut slip

We are bias believers in the CCP studio! Bias-cut garments have a totally different flow and drape than anything cut on the straight grain, and have a slinky, clingy, almost liquid effect when worn. In this post, we are going to dig into tips for sewing on the bias since there are some special considerations and modifications you need to make if you want to tackle the joys of bias sewing.

First, what does sewing or cutting on the bias even mean? Most garments are cut on the straight grain, which means the grainline of the pattern piece is aligned parallel to the stable, vertical grainline of the fabric. This creates some degree of structure and stability – unless you’re working with a naturally stretchy fabric like a knit, the garment will not end up stretching much around the body. With a bias cut garment, the grainline is actually rotated 45 degrees (aka the bias) where most woven fabrics naturally have more mechanical stretch and give. If you need a visual, cut a perfectly square piece of fabric and try stretching it side to side and then along the diagonal – you’ll see that it has much more stretch along that diagonal line than horizontally or vertically. This natural, mechanical stretch is what gives bias-cut clothing that drapey, fluid form.

We designed our Simone slip, dress and camisole to be cut on the bias so it could drape and mold elegantly around the body. It was inspired by the clinging silhouettes French couturière Madeleine Vionnet created by utilizing this pioneering technique in the early twenties, and one hundred years later, this magic trick of sewing continues to yield the most elegant style lines. It’s fun to watch couture runway shows and point out all the garments that are cut on the bias. Hard to imagine high fashion without this contribution to the vocabulary! 

FABRIC SUGGESTIONS FOR SEWING ON THE BIAS

It is REALLY important to start with the right fabric when approaching a bias-cut garment. For best results, look for drapey and fluid woven fabrics like silk crepe, satin, chiffon, georgette, viscose or rayon challis. If you are new to sewing on the bias, we suggest avoiding very slippery fabrics like silk charmeuse and satin since they can be tricky to work with at the best of times. Avoid stiff wovens, as they are too structured and will not drape and conform to the body, and may end up fitting too small since the fabric doesn’t have as much natural stretch as more fluid options. Below you can see some examples of fabrics we’ve used to sew Simone; all give a gorgeous fluid effect.

 

FINDING THE BIAS

Cutting fabric on the bias means the grainline of the pattern piece is not aligned with the straight fabric grain like traditional garments. Instead, it is aligned with the true bias, which runs at 45 degrees across the fabric in two directions. The bias direction naturally has more stretch and malleability since it is not stabilized by the straight grain or cross grain. This means it has more drape and fluidity, and will conform to the shape and contours of the body.

While the pattern pieces of Simone are precisely marked to help you correctly align with the bias grain, knowing how to find the true bias is a useful skill. To determine its location, start by marking the lengthwise grain by marking a line parallel and close to the selvedge. Next, use a 45 degree triangle ruler or the 45 degree lines on a quilting ruler with the line you just marked. If your ruler isn’t long enough to reach from edge to edge, extend the line with a longer ruler. Lay your pattern pieces out to align with this edge or in the case of the mirrored pieces, opposite to. You can stretch a string across your cutting service and pin or tape to the table top, sliding your pattern pieces underneath. Or run several strings if your pattern is very large.

HANG TEST FOR STRETCH 

If you want to see if your fabric is a good candidate for bias-cut sewing you can hang a sample for a day or two.  Cut a square parallel to the selvedge to precisely measure 4” (10cm) along each side. Cut a square of the same size on a piece of paper. Pin them both vertically by any one of the points and allow them to rest for 24 hours. Your fabric will either “drag” or “drip”, or it will “float” or “lift”, to borrow terms coined by Charles Kleibacker, another couturier famed for his mastery of the bias. In other words, the former will have a liquid quality and will soon stretch from point to point, becoming clearly more lozenge-like in comparison to the paper square. The latter will retain its shape, having a crisper nature. While both qualities are attractive, the former is required for the Simone slip dress.

LAYING OUT YOUR PATTERN

  • Bias-cut garments MUST be cut on a single layer in order to ensure correct grainline placement. If you are sewing Simone, take care to study the cutting layout, as the pieces must be cut in a specific direction and arrangement in order to properly drape on the body. If the front and back are cut on the parallel bias, the slip will twist. In our cutting layouts, we cut the front and back with bias perpendicular to one another–this ensures the slip is balanced. Use labels to identify pieces that look very similar when you are cutting and preparing your pattern. 
  • Drapey fabrics can be a little more challenging to work with since they tend to shift and are easily distorted. All fabric edges must be supported while cutting; an end hanging off the table will drag and misalign the fabric. Roll up any portion of the fabric that is too long for your cutting surface.
  • Pattern weights are your friend. If you don’t have enough you can use anything! Cans of beans, hockey pucks, flat rocks, magazines, anything to keep as much of the fabric as flat as possible and not shifting around. Take the extra time in the beginning to carefully weigh everything down and you’ll save time down the road.

CUTTING TIPS FOR BIAS-CUT GARMENTS

  • Using a sharp rotary cutter ensures minimal fabric manipulation. Start by loading yours up with a freshy fresh blade. Now is not the time to skimp on prep! If using scissors, a pair of micro-serrated shears prevents delicate fabrics from slipping when cut.
  • Ensure all construction marks are transferred to your fabric using a removable marking tool or tailor’s tacks. Mark the seam allowance on your pieces with a removable marking tool or a basting stitch. This ensures you know where it is even when your pieces stretch later.
  • Handle the cut garment pieces carefully. Pieces should be stored flat–only hang longer cut pieces such as skirt or dress panels that you want to stretch out before trimming and sewing.

SEWING FABRIC ON THE BIAS

Bias seams need to stretch along with the body of the fabric, particularly along side seams. However, different fabrics require different approaches. The best way to determine which method suit your project best is to test several stitching methods.

Two that have proved successful for many are the following: 

  1. Slightly stretch the seams as they are being stitched to build in maximum stretch to your seam line. This tension will cause the seam allowance to narrow; ensure you adjust the seam allowance width as you sew accordingly. Marking your seam lines before you start sewing will help guide you.
  2. Use a narrow zigzag seam with a width of 0.5mm and a length of 2 to 2.5mm. If you choose to sew a narrow zigzag, try not to stretch your seam as you sew since you may be building too much stretch into the seam.

It’s important to utilize stay-stitching anywhere the pattern recommends it. This ensures necklines, arm holes or waistbands don’t stretch out when being handled and sewn. On pockets, or areas where a zipper or other closure will be sewn, stabilizers are a good idea. A lightweight, knit/stretch iron-in interfacing is perfect for these high-traffic areas, which should be applied to the wrong side of the fabric using light stream and a press cloth. This brings me to the next point…

PRESSING & FINISHING BIAS CUT GARMENTS

  • Use a press cloth for delicate fabrics.
  • Often steam alone can do the work of a hot iron without the danger of burning your fabric. Make sure to always follow the instructions if you know what kind of fabric you are using and testing a small area if you don’t!
  • When pressing, ensure you’re using an up and down motion; sliding your iron around can distort the fabric.
  • Use a tailor’s ham when pressing curved areas.
  • We suggest finishing all seams, although it’s not obligatory since bias cut fabric does not fray very much. For an elegant finish, choose a French seam. You may also finish with a serger. 

BALANCING THE HEM

When sewing on the bias, you may find your hemline is uneven. This is due to the fluid nature of bias-cut garments and is to be expected. To correct it (aka balance the hem), hang your garment for a day before sewing the hem. With a friendly fitting partner or a dressform, try on the garment without shoes. Hold a yardstick with the end on the floor. After determining your preferred length,  mark the new hemline measurement around the entire circumference of the hem. Trim and hem as instructed.

One final note about hems: since you are folding and pressing on the bias, you’ll get best results by sewing a narrow or baby hem. Wide hems are not suggested for bias-cut garments since it is difficult to get them to lay flat.

Now go forth in your new slinky garment and let the memory of Madeleine Vionnet live on!

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Hi! I'm Heather Lou, a pattern designer and sewing educator for the modern maker. At Closet Core Patterns, we transform your imagination into step-by-step implementation that helps you create a wardrobe you love - not one you're limited to buying off the rack.

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