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To test cord strength, stretch and set, secure a thread or string to be tested around a smooth, round surface. Take a couple of turns before tying off. If secured properly breaks will occur randomly along a strings length. If secured improperly, breaks will occur near the fastened ends. If a string is to be used by itself, or in parallel with others test a section several feet long. This will reveal the strength of its weakest point. If a string is to be twisted together with others in a cord, determine its average breaking strength: first break long sections to find its weak-link strength as above. Then break several three to five inch sections to find its strongest-link strength. Take several readings, then average them out.

To measure stretch and set - the amount a string will remain stretched when tension is released - lay out fifty inches of thread or cord. Wrap one end of cord twice around a smooth, round dowel before tying off at a nail or such. Attach the other end similarly to a scale. Place a ruler beside the scale. Pull the scale, applying tension slowly and repeatedly, building up to point of breaking. Note the amount of stretch, and the amount of set as you proceed, as well as the point of failure.

Offered by Brian.