BLIND CORD 1.1 MM BREAKING STRENGTH 35 kg to break point
Thin cord for light-duty applications. How much does it really hold before it snaps?
The 1.1 mm blind cord breaks at an average of 0.34 kN, equivalent to 35 kg.
You might expect a thin cord like this to be overshadowed by thicker ropes. Yet this blind cord shows something notable: it stretches considerably before breaking, far more than you'd expect from such a thin cord. That elongation says more about its intended use than the break point itself.
Five measurements on a universal testing machine produced results between 0.33 kN and 0.35 kN. The spread stays limited to 0.02 kN, making this cord predictable in behaviour despite its low break point.
1.1 mm blind cord: material and construction
This cord is made of polyester and braided without a core. Polyester absorbs almost no water, so it loses very little strength when wet. The cord also holds up well against UV exposure.
The core-free braid keeps the cord thin and flexible, which suits its purpose: blind cord is used to operate slats or other blind components, not to carry heavy loads.
How we test
Breaking strength tests are carried out in-house by Otto Tromm on a universal testing machine with a capacity of 50 kN. Two sets of specially developed rope clamps are available for this machine, used depending on the rope's diameter and material. These clamps allow rope to be tested without first being spliced.
All tests are carried out according to the ISO 2307:2019 guidelines. This means, among other things, that each test is repeated 5 times at a test speed of 20 mm per minute. Each rope is secured so that it sits taut. No pre-tension is applied, since these tests do not measure elongation.
The tensile test itself is filmed: two repetitions of each test are recorded with a Sony camera on a tripod. The graph's progression is no longer filmed separately.
The testing machine exports the measurement series as a data file: 20 measurements per second, with force in kN and displacement in mm. These files are saved per measurement.
The graph in this report is plotted directly from that data, so it represents the measured series itself, not a reconstruction or a video excerpt. For this test, that amounts to 12,213 data points over 611 seconds.
For each of the 5 tests, the tester records written observations, capturing details such as the degree of elongation, the way the rope breaks, and the loudness of the snap when the rope fails.
Results of the breaking strength test
The five measurements are close together: between 0.33 kN and 0.35 kN. That's a spread of only 0.02 kN, indicating a consistently produced cord.
What stood out was the behaviour during the test, not just the outcome. The cord stretched considerably more than, for example, a 0.8 mm or 0.9 mm Dyneema cord.
The force build-up was also erratic: the force rose, then dropped back, then rose again once the elongation eased off. This happened in small steps of 0.01 kN each time.
The cord did not break in one smooth pulling motion but in a series of small jolts.
Keep this in mind: the reported break point is the average of five measurements with this erratic force curve.
How does this cord compare to other ropes
Only this cord's own measurement is available. No direct comparison with other products from this test has been made.
With a breaking strength of 0.34 kN, equal to 35 kg, this cord clearly falls into the light-duty category.
Compare that, for example, with the 0.8 mm and 0.9 mm Dyneema cords mentioned in this test: this blind cord stretched noticeably more than those cords.
When to use this blind cord
The low break point of 0.34 kN determines what this cord is and isn't suited for.
✓ Suitable
- Operating blinds and slats — the cord is designed for this purpose, and its thin diameter fits small guides
- Light household applications — think roller blinds or decorative fixings without tensile load
- Crafts and hobby work — the fine 1.1 mm diameter suits precise handwork
✕ Not suitable
- Any form of lifting or carrying — the cord breaks at 35 kg, too low for securing objects
- Outdoor applications under heavy tension — the substantial stretch makes the cord unsuitable where stability is required
- Situations involving shock loading — the erratic force build-up during testing shows that the cord does not respond evenly to sudden tension
Conclusion: suitable for blinds, not for load-bearing use
The 1.1 mm blind cord achieves an average of 0.34 kN, equal to 35 kg, with an erratic force build-up and significant stretch before breaking.
Use this cord for blinds, slats, and light craft work. For applications where tensile strength or stability matters, a thicker or stiffer cord is a better choice.
Otto Tromm personally counted the small 0.01 kN steps on the testing machine. He now calls it his most relaxing measurement so far.