A header is created by weaving scrap yarn before starting a project. Its purpose is to spread the warp evenly so there are no gaps in the warp and to give your cloth a firm foundation to grow. You may be tempted to skip this step and in some instances that may be ok, but here’s why I think weaving a header every time is a grand idea.
Unlike floor or table looms the rigid heddle isn’t secured to the loom. It hangs freely when you release it from the heddle block. You have to guide the rigid heddle to the fell of the cloth—the last woven pick—with your hands. One side of the heddle will always hit the fell line before the other. Typically the side of your non-dominant hand will hit first because you have less control over it.
If you don’t have a header you may notice that one side of your cloth grows faster than the other causing your weaving to grow at a slight angle. This isn’t the only reason this happens, but it is one of them. You can adjust the spacing of the weft as you weave to correct the angle. This may or may not cause you issues in your final cloth. If you are weaving with wool these gaps will most likely fill in. If you are weaving with linen then these gaps will be more obvious. Fine threads tend to show irregularities more than thicker ones.
There is also the issue of finishing. If you are hemstitching having the yarn spread evenly will ensure that your stitches are even. If you are knotting the header will keep your weft in place until you are ready to finish. For this reason when I am knotting I also weave a header at the end of my project as well as the beginning. If I am securing the weft by stitching the second header isn’t necessary.
I like to use a smooth cotton scrap yarn that contrasts well with the warp so it is easy to distinguish from the other yarns in my project and is easy to remove.
There is rarely a wrong way to do things. If it gets the job done and you like doing it then by all means do it. You don’t have to weave a header to create a good piece of cloth, but I think they are a good habit to get into.
If you like these kinds of tips check out Life After Warping. In this video I walk you through all these kinds of weaverly details on how to weave great cloth after your loom is warped.