Call me old fashioned, but I continue to be a huge fan of adding piping to both clothing and interior decoration projects. I do it on the doll clothing I design for Doozie For Dolls, I do it on clothes for real people, and I do it on slipcovers too! Piping is a way to define or outline a portion of a project, and to enhance the design details.
The word piping is usually used when discussing clothing, and the word welt is usually used on interior decoration items. Both of these terms refer to a long strip of cloth cut on the BIAS that encloses a soft cotton cord, and then is sewn into a seam. Smaller cords are usually used for garments, and larger cording is used for upholstery projects.
You can purchase manufactured piping in 4 yard packages, with all the work done for you, but pre-made piping usually comes in only a limited range of colors. You can also easily make your own piping or welt, either from a fabric that matches your project, or, preferably, from a contrasting fabric. It's the contrast that accentuates the design detail. While it is traditional to use a solid color piping or welt with a printed base fabric, I find it fun to mix prints.
Bias is the diagonal cut of a woven fabric, cut on a 45 degree angle. The lenthwise grain of a woven fabric refers to the threads running parallel to the selvedge of the cloth and the crosswise grain of a woven fabric refers to threads running at right angles or perpendicular to the selvedge. Bias is diagonal to these two grains.
The primary characteristic of bias is that it stretches. Before knits were readily available, the stretching quality of a bias cut was used to help fabics cling to the body, and move with the body. Think of those great draped gowns from the late 1930s and 40s. That look was achieved by using the bias attributes of the cloth.
Bias is useful with piping and welt because it allows them both to follow the lines of any section of the garment, going around curves. Think of a round yolk on a child's dress, or the curved yolk lines on a cowboy shirt. These design lines are more apparent when they are 'outlined' in piping, and the piping will lay better when the fabric is cut on the bias.
MAKING YOUR OWN PIPING/WELT
The first thing you need to decide is what size cording will work best with your project. Large sewing supply stores will usually stock a number of different sizes, which you can purchase by the yard. For slipcovers and decorative pillows, our workrooms usually use 1/4" cording. For garments, I keep lengths of smaller cord on hand, judging the size by eye rather than diameter. It is important that the piping or welt be in scale with the project on which you are working.
Next you will need to figure the width of the bias strip cuts. Select some cording, and then cut a 5" length of fabric on the bias to wrap around it. The width of your cut will depend on a) how much seam allowance you wish to have on the welt/piping and b) how much fabric it takes to go around the cord. The best way to figure this out to to try a section with the actual cloth you intend to use, for some of the more heavy, upholstery fabrics will require more width to actually go around the cord and form the seam allowance. For interior decoration projects we normally plan for a 1/2" seam allowance, but for clothing projects, you can have as little as 1/4" (which is the standard for the pre-made piping) up to 5/8", which is the width of the seam allowancs on most patterns. Proceed to cut as much bias stripping as you will need.
CUTTING BIAS STRIPS
To cut bias strips, first determine the width of your cuts (see above) and then determine approximately how much piping/welt your project requires. This varies quite widely (an upholstered side chair may require 10 yards of welt if it has two boxed cushions.) If you are simply adding welt to an 18" pillow, you will only need just over 2 yards. If you're adding piping to the yolk of a garment, measure the seam length on which the piping will be applied (remembering to double it if you are cutting two pattern pieces) and cut a few inches more just to be on the safe side.
To prepare to cut bias strips, first one raw edge of the fabric straight across from right to left. Working with a single layer of fabric, pick up the lower left hand corner of you fabric and move the cut side (cross grain) on the diagonal until it lines up with the selvedge, forming a triangle of fabric with a fold on the diagonal. Make a second crossgrain cut of your fabric through one layer only across the top, separating your triangular piece from the rest of the yardage. Next, slip your scissors in the fold and cut it completely apart, allowing the top piece of fabric to land right on top of the bottom piece. This cut edge is the BIAS, and it must be handled very carefully so it does not stretch during the cutting process.
Next, mark the width of the bias cuts you need. We have found that many of the metal yard sticks in our workrooms are just the right width for certain sizes of welt. For piping, I usually use my clear plastic ruler that is cross marked in 1/8" lines, making chalk marks at the prescribed width on either end, and then lining up a yard stick between those marks.
To prevent distortion of the bias, I usually cut my strips using a rotary cutter and a special mat. I place the yard stick at the proper mark points, and run the cutting disk right along it, carefully holding the yard stick in place.
At the beginning of the cutting process, I enter the total number of inches I will need onto my calculator. As I rotary cut each PAIR of strips (remember, you have two layers of fabric) I measure them and subtract that amount from the total I need. I continue to do this until I have more than enough inches to do the project.
When you finishing making your cuts in this manner, you will usually have an angle cut at each end of each strip. This cut will actually be on the STRAIGHT GRAIN of the fabric, for the long cuts are all on the bias. To create the length of bias strip you need for your project, you will sew these angled cuts end to end until you get the total overall length you need. I normally use only a 1/4" seam allowance to join each section, and to further reduce bulk, I cut away any selvedge before I make the seam. Once all the pieces are joined, I press each seam open and flat, taking care not to let the length of the bias strip hang down from the ironing board and thus risk stretching out.
MAKING THE PIPING OR WELT
Now that you have the full lenth of bias strip that you need for your project, the next step is to wrap it evenly around the cord you have chosen. Working at your machine with thread that matches your bias fabric, fold the bias strip in half, encloing the cord in the fold. To prevent stretching during this part of the project, keep the length of unsewn bias strip supported, either on your table or on your lap, so that it is not unduly stretched while it is being sewn. Using your zipper foot, sew a line of basting stitches through both sides of the fabric to secure the cord inside your bias tube. but DO NOT PLACE THE STITCHING RIGHT UP AGAINST THE CORD. Instead, have your stitch line just a bit away from the cord. This is important to avoid any stitches showing later on in your project. Continue to enclose all the cord in the bias strip until you have enough piping/welt for your whole project.
APPLYING PIPING OR WELT
Once you have all of your piping/welt made, you are ready to apply it to your project. Let's say your are applying it to the circular yolk of a child's dress. First, you will sew the shoulder seams of the yolk together and finish them, to that the total yolk is formed.
Then, working on the right side of the fabric, pin the piping so that the cord lies right on the seamline all around the yolk. DURING THIS PHASE, IT IS IMPORTANT TO HANDLE THE PIPING GENTLY AND NOT TO PULL IT. While one usually keeps a certain tension on fabrics being sewn together, if you pull on piping (or bias of any kind, actually) during the sewing process, it will cause puckering in the base fabric.
Next, baste the piping to the yolk piece, once again, not stitching right up tight against the cord, but allowing the stitches to run just slightly to the side of the cord. If you are sewing the piping onto the yolk freehand, without first pinning it, you must actually PUSH THE PIPING INTO THE PRESSER FOOT rather than keeping a manual tension on it. If you pull on piping or welt, it will cause the base fabric to pucker, and would thus affect the size of the piece on which you are working. Learning how to handle piping and welt so as to not cause distortion of your project is the most important part of working with these kinds of projects. Practice before you use that $100 per yard fabric!
JOINING WELT (Putting welt on a pillow top)
While most piping projects don't require a fancy joining, things become more tricky when you are working with welt, which is much larger and more bulky. As an example, let's pretend that you're applying welt to the front face of a decorator pillow.
First, unstitch about 6" of the welt you've made. Using standard masking tape, wrap a band of tape around the cord about 4" in from the cut end. Cut the cord only right through the tape and throw away the 4" tail. Mark the center point of the bottom edge of your pillow top. Place the welt where the stitching begins just a bit to the right of this center point, lined up with your stitching line and begin to apply the welt to the pillow top, leaving the uncorded tail section unsewn. Once again, do NOT stitch right up against the cord in the welt, but keep the stitching just to the side of the welt, and PUSH the welt into the presser foot, do not pull it.
Stitch from near the center to 1" from the first corner. Stop stitching with the NEEDLE DOWN. At the exact point where the welt will turn the corner of the pillow, make a small cut in the welt, not going in as far as the cord. Re-commence sewing and sew right up to the corner point. Stop with the needle DOWN. Rotate the whole project, allowing the cut in the welt to open up right at the corner. Continue to apply the welt to the pillow top, pushing the welt into the presser foot and treating each of the corners the same way. When you get about 4" away from your starting point, stop.
At this point, you can remove your project from the machine. Later on, you will be able to do this next step right on the machine, but while you're learning, this will be easier.
What you should see in front of you is a pillow top with welt sewn around about 95% of the perimeter. Overlap the left side welt end with the cord still enclosed about 4" past the center mark on the pillow and cut off the remaining welt. Next, unstitch the basted welt holding in the cord back about 6", just as you did at the very beginning of this section.
You will now have two separate things to join. You need to join the bias strips, and you need to join the thick cording that forms the welt. Think of these two things separately.
First, you'll join the BIAS STRIPS. Remember how they were joined as you were forming the long strips! The ends were cut at a 45 degree angle, along the straight grain of the fabric. Cut the end of the right hand bias strip at such an angle if it is not already thus. Lay it down towards the left on the edge of the pillow. Now take the left hand bias strip which you have just unstitched from the cord and place it over the right had strip. You will need to seam these two pieces. If you cut the right hand strip 1/2" longer (all along the diagonal) than the point where they overlap, you will end up with the perfect length of strip. BEWARE TO CUT THE RIGHT HAND STRIP AT A DIAGONAL THAT MIRRORS THE LEFT HAND CUT, i.e.with the slanted cut going the same direction. When you're a beginner at this, pinning the sewing line before you cut just to make sure you've got it right is a safe idea. Sew a 1/4" seam to join the two ends of the bias strip and press the seam open with your fingers. Now the bias strip is joined.
Second, you will join the CORDS. You'll recall that one of them has already been bound in masking tape and cut. Lay the piece of right-hand cord flat along the edge of the pillow towards the left. Take the left hand section of the cord and lay it out toward the right until it lays flat along that edge of the pillow. Place a collar of masking tape around the left section of cord, centered on the point where the two cords cross. Gently tug each cord to lay flat, and mark the masking tape on the left side cord at the point where the two cords meet. Cut the left hand cord. Now, take another piece of masking tape, and tape both cord ends together, butting them against each other.
Now the cords are joined and the bias strips are joined. Place the cord inside the strip, and continue to baste it onto the pillow until all the welt is applied. You have now successfully joined the more bulky welt.
SEWING PIPING/WELT INTO SEAMS
The final step in applying piping or welt is to enclose it into the seam which it is to accent. Let's use the pillow as our example. Get the back section of the pillow, and place is face town on the front section to which you have applied the welt. Pin the two sides together at each of the four corners.
FLIP THE PILLOW FACES OVER SO THAT THE WRONG SIDE OF THE FRONT FACE IS FACING YOU. Beginning 4" to the left of a corner, sew through all layers using your zipper foot. At this final stage, it is crucial that you push the side of the zipper foot as close to the welt as you can possibly get. You will see the former line of stitching that attached the welt to the pillow top, and you need to get closer to the welt than that line of stitching. The larger the welt, the more difficult this step can be on a home sewing machine (it is somewhat easier on an industrial walking foot machine.) Still, you can do it! You can even manually push the welt with your left hand up against the edge of the presser foot. Continue to sew around the pillow until you are about 4" past the final corner. Back tack, turn the pillow right side out, and hand stitch the opening closed once the pillow form has been inserted.
When you're sewing piping, which has much smaller cording, getting a close stitch is easier. You may also want to try basting the two sections together first and then sewing a second time using a smaller stitch length, and again, pushing the zipper foot up tight against the cording. With piping, you have to be careful not to inadvertantly go too far and go over the piping. Practice! The results are such fun!
PS I know that this section, more than most, could benefit from photos. I'll do it when I have some more time!