All the yarn packages in one warp should be of the same type (spools, or cones, or balls) and about the same weight. If they differ substantially, the warp’s tension will be uneven. To see why, try this test. Pull gently on the end of yarn coming from a large cone. Then pull gently on the end of yarn coming from a small spool. Feel the difference in the amount of “drag”? That difference in braking power will translate into different tensions and different lengths. And different tensions will translate into weaving problems. You can even out the tension of yarns on different packages with a tension box.
The Tension Box
A tension box between the yarn packages and the warping board or reel can even out the tension of yarns.. Use it for a mixed warp, when by their nature the yarns behave very differently, or when different types or sizes of yarn packages are necessary. If you don’t get enough tension using all the rods on the box, you can spiral the threads around one peg twice for extra tension. If you don’t have a tension box, run the threads in and out of a spool rack, ladder back chair or reed to get the threads all under the same tension. Some yarns, particularly metallics and some rayons, unwind extra fast. Especially in a mixed warp, you’ll need to slow these yarns down. A good way to do this is to weave the yarn under and over several bars on the creel. This puts more drag on these threads and slows the spools down.
Read about vertical creels, horizontal spool racks, and other warping equipment on pages 17-25 in Book No. 1., How to Wind a Warp & Use a Paddle