Check three properties of every batch of yarn against what the loom will ask of it: count by weighing a measured length, twist by untwisting a sample, and breaking load by pulling single ends on a spring balance. Spot tests catch a drifting frame but cannot certify a warp, because 20 samples of half a metre inspect only 0.005% of a 100 m warp of 2,000 ends, so the number of ends that break per hour on the loom is the final measurement.
Part of Spinning Frame
Measuring and maintaining yarn that is consistent in thickness, twist and strength, with the loom’s warp requirements as the standard.
The Loom Sets The Specification
Yarn is not good or bad in itself. The Power Loom Construction overview holds each warp end under tension for the whole piece and rubs it through a heddle eye and reed on every pick; weft is used once. So the same frame must meet two different standards. The yarn trees and the loom trees are written to the same reference: a medium yarn of Ne 20, 29.5 tex (Thread Count System).
| Property | Warp | Weft | Where it is set | Where it bites |
|---|---|---|---|---|
| Twist | 18-25 per inch | 12-18 per inch | Twisting | Shedding: heddle and reed abrasion |
| Count | Even along its length | Even | Drafting | Beating Up: thick places jam, thin places break |
| Breaking load | Well above the tension per end | Modest | Twist Testing | Warp Tensioning and Let-Off |
| Surface | Smooth or sized | Softer | Mechanical Carding | Warp Beam: sizing |
Soft, low-twist yarn is the failure the table exists to stop: it passes as weft but frays against the reed and parts under tension as warp. The overview’s own range of 18-25 twists per inch marks the boundary.
What Each Test Tells You
- Count. Wind a known length on a reel and weigh it. A 100 m skein of 29.5 tex yarn weighs 100 × 29.5 ÷ 1,000 = 2.95 g, so a balance reading to 0.03 g gives about 1%. One metre weighs 29.5 mg, too little to weigh reliably.
- Twist. Count turns per length; Twist Testing gives the method and its resolution.
- Breaking load. Pull a 50 cm sample to break on a spring balance and note the force. The weakest sample matters more than the mean, since the loom breaks at weak places.
- Evenness. Wind yarn side by side on a dark board and look for thick and thin places.
- Ends down per hour on the loom. The only test that covers all of the yarn.
The Sampling Arithmetic
A warp of 2,000 ends 100 m long is 2,000 × 100 = 200,000 m of yarn. Twenty samples of 0.5 m are 10 m, which is 10 ÷ 200,000 = 0.005%. A weak place one metre long in 200,000 m would almost never fall in a sample. So spot tests are for finding drift, such as count wandering, twist falling with tape slip (Drive System) or roller faults (Drafting Rollers). They are not a guarantee, and the acceptance test of a new batch is a trial warp on the loom, with ends down counted.
What You Need
- A balance and a reel of known circumference.
- A spring balance for single-end pulls.
- A needle and a ruler for twist counting.
- A dark board and a record book.
Method: Testing At Every Doff
Step 1: Take a sample bobbin from the doffed rack, never from a running frame (Doffing).
Step 2: Weigh a skein to find the count, then compare with the target.
Step 3: Test twist on five samples from different layers.
Step 4: Pull 20 ends to break; record lowest and mean.
Step 5: Log the numbers by frame and spindle and plot them over time.
Step 6: Weave a trial warp from any new batch, a short one, and count the ends down.
Worked Example
The target is 29.5 tex. A 100 m skein weighing 3.10 g is 31 tex, 5% heavy, which is a thickness drift that needs the draft re-checked. A skein of 2.95 g is on target. In the same bobbin three twist counts of 19.0, 19.2 and 18.8 twists per inch (inside the warp range) are acceptable for warp; three counts of 14 would pass for weft only.
Common Mistakes
- Testing weft-quality yarn against the warp standard, or the reverse.
- Reading the mean. One weak place is a stopped loom.
- Skipping the loom trial because the bench tests passed.
Safety
Sample from stopped machinery only
Never pull a test thread from a running frame or reach into a running loom for a sample. The frame is stopped and its drive locked before any hand goes in; see Doffing and Drive System. Quality checking is a job for trained adults on stopped machinery; the corpus keeps children away from running machinery (Task Assignment by Age).
What’s Next
- Learn next: Thread Count System — the units used above
- Combine with: Warp Tensioning and Let-Off — what the warp actually has to bear