Why Does Yarn Moisture Regain Matter?

Three Common Signs on the Production Floor

Changes in Yarn Weight

During transportation, storage, and production, yarn continuously exchanges moisture with the surrounding air.

In a dry environment, the yarn may gradually lose moisture. In a humid environment, it may absorb additional moisture. As a result, the same batch of yarn may show different weighing results after being stored under different conditions.

This difference deserves more attention when the yarn contains highly hygroscopic fibers.

For delivery measurement or settlement, do not rely only on one weighing result. Both parties should confirm the measurement method, test conditions, and weight conversion basis in advance.

More Static, Fly, and Yarn Breakage

When yarn becomes too dry and the workshop air also has low humidity, electrical charges are more difficult to release. Static electricity may then become more noticeable during production.

As static increases, fly, fiber adhesion, and yarn entanglement may also become more serious.

During unwinding, yarn passes repeatedly through guide parts, tension devices, and knitting needles. If the fiber surface becomes excessively dry, the friction condition may change. Some yarns may then show more hairiness, end breaks, or unstable running performance.

However, the final result also depends on the fiber type, yarn structure, workshop temperature and humidity, machine speed, and yarn path.

Sticky Hand Feel and Unstable Winding

Excess moisture may give yarn a sticky hand feel and affect its unwinding or winding performance.

For natural or regenerated fibers with high moisture absorption, long-term storage in a damp environment may also increase the risk of packaging problems, mildew, unpleasant odors, and shade changes.

Therefore, yarn is not always better when it is drier. It is also not better when it contains more moisture. The key is to keep the yarn within a suitable moisture range.

Moisture Content and Moisture Regain

These two terms often appear together, but they use different calculation bases.

Moisture content: The percentage of water in the total weight of the wet material.

Moisture regain: The percentage of water compared with the dry weight of the material.

For example, if 100 grams of dry yarn absorbs 5 grams of water:

• Moisture regain = 5%
• Wet weight = 105 grams
• Moisture content = approximately 4.8%

Therefore, moisture content and moisture regain cannot be used interchangeably. Before reviewing a test report, confirm the exact term and calculation method.

The textile industry also uses the term official moisture regain or standard moisture regain. This value supports weight conversion under specified conditions. However, it does not represent the actual moisture level of every yarn batch in every environment.

Why Can Warehouse and Machine Performance Differ?

Yarn may move from the supplier’s warehouse to the customer’s warehouse and then into the production workshop. During this process, the temperature, humidity, and packaging conditions can all change.

After yarn enters a new environment, the moisture level on the surface and inside the yarn may not reach equilibrium immediately.

If the yarn is weighed, unpacked, or used on a machine too soon, the result may not reflect its stable condition.

In production, “moisture conditioning” usually means allowing yarn to rest under a controlled temperature and humidity level so it can gradually reach a new moisture balance.

This process differs from simply spraying water or adding moisture directly. If the surface becomes wet while the inside remains relatively dry, the uneven moisture distribution may affect later processing.

Different Fibers React Differently to Moisture

Cotton, viscose, wool, and flax generally absorb more moisture. Polyester, nylon, and acrylic show different moisture absorption behaviors.

Moisture also affects the strength of different fibers in different ways:

• Cotton usually becomes stronger when wet.
• Ordinary viscose often loses strength in the wet state.
• Wool may also lose strength when wet, although the degree varies with the fiber type and treatment.
• High wet modulus viscose and high-tenacity viscose require product-specific evaluation.
• Synthetic fibers should not be judged according to the same rules as natural fibers.

Even when the fiber type remains the same, yarn count, twist level, blend ratio, hairiness, and packaging condition can change the final performance.

What Should Be Confirmed Before Production?

Before placing yarn on a machine, confirm the following points:

• Fiber composition and yarn structure
• Any agreed moisture regain or moisture content requirement
• The weighing environment and conversion basis
• Storage conditions and pre-production resting requirements
• The method for retesting and handling abnormal results

When comparing moisture data from different batches, keep the sampling location, test method, environmental conditions, and test timing as consistent as possible.

For example, one sample may have just been removed from its package while another has remained in the workshop for several hours. Their test results may not be suitable for direct comparison.

For highly hygroscopic fibers, fine-count yarns, or products that require stable machine performance, observe the actual unwinding, hairiness, end breaks, and knitting conditions before production.

Test data provides an important reference, but actual machine performance matters just as much.

What Is Moisture Regain Really Meant to Solve?

Moisture regain is not about making the number as high as possible. Its purpose is to keep yarn in a suitable condition for storage, weighing, and processing.

To determine whether yarn requires moisture conditioning, look beyond one data point. Consider the fiber type, yarn structure, storage environment, production equipment, and processing method.

Moisture may seem like a minor yarn characteristic, but it can affect weight, hand feel, static electricity, hairiness, end breaks, and production efficiency.

Reference Standards

The following standards may be used as references:

• GB/T 9994-2018, Official Moisture Regain of Textile Materials
• GB/T 9995-1997, Determination of Moisture Content and Moisture Regain of Textile Materials by Oven-Drying Method
• GB/T 6503-2017, Test Method for Moisture Regain of Chemical Fibers

Different fibers, yarn structures, storage environments, test methods, and processing conditions can influence actual moisture levels and production performance. The final evaluation should always follow the requirements of the specific product and test conditions.