Calculating Multi Fibre Blend Regain Allowance for Customs Valuations
Customs valuation for multi-fibre blends requires deriving commercial mass by adjusting clean oven-dry weight with ISO 6741 weighted fibre regain allowances.
Wool Keratin Regain
Fiber Absorption
Natural moisture management properties characterize the protein structure of animal hairs, allowing them to hold a significant amount of water vapor without feeling damp to the touch. Wool keratin regain is the technical term for the percentage of water that a dry wool fiber will naturally absorb from the air under standard temperature and humidity conditions. This ability comes from the hydrophilic amino acids within the keratin molecule, which attract and bond with water molecules.
Because the weight of wool can fluctuate by more than fifteen percent depending on the environment, this metric is used to standardize the commercial weight of the material for trade. It ensures that a buyer is paying for the actual protein fiber rather than the variable weight of the water it contains. The standard regain for wool is generally set higher than for most synthetic fibers.
Processing Environment
Maintaining the correct level of humidity in the spinning and weaving mill is essential for handling fibers with a high wool keratin regain. If the air is too dry, the fibers become brittle and prone to breakage, and they generate static electricity that makes them difficult to align. If the air is too damp, the fibers can stretch too much and may even begin to rot if stored for long periods.
Mills use sophisticated climate control systems to keep the moisture level at a constant point that optimizes the strength and elasticity of the yarn. This environment also ensures that the weight of the material remains consistent as it moves through the different stages of production. The regain property is what gives wool its famous comfort, as it can absorb sweat from the wearer and release it into the air.
Commercial Standard
International trade agreements specify the official wool keratin regain values that must be used when calculating the weight and price of a shipment. These standards, such as those set by the iwto, provide a common language for farmers, traders and garment manufacturers around the world. When a bale of wool is sold, it is tested to find its oven-dry weight, and then the standard regain is added to reach the commercial weight.
This process eliminates the disputes that would otherwise occur due to the changing weight of the goods during transit. It also allows for the comparison of different lots of wool on a fair and equal basis. The high regain of wool is one of its primary advantages over polyester, which has a very low natural moisture absorption.
Structural Integrity
Interaction between water and the keratin protein is what gives wool its unique physical characteristics, including its ability to be shaped with heat and steam. The wool keratin regain process is reversible, meaning the fiber can take on and release moisture many times without losing its strength. However, extreme changes in moisture can cause the fiber to swell and shrink, leading to the felting and pilling that can occur during washing.
Understanding this behavior is critical for the design of wool garments that will maintain their shape over time. The regain also affects the dyeing process, as water acts as a carrier for the dye molecules to enter the core of the fiber. This natural mechanism is a perfect example of how the chemical structure of a material determines its industrial and commercial behavior.