Calculating Raw Linen Greige Off-Loom Mass Loss

Moisture

Freshly woven linen rolls contain variable moisture levels that can distort baseline inventory weights. Because flax fibre is inherently hygroscopic, it absorbs or releases water vapor until balancing with surrounding air. Standard testing under ISO 139 calls for twenty degrees Celsius and sixty-five percent relative humidity, but actual weaving shed conditions rarely match those benchmarks.

Air-jet sheds run at higher humidity to reduce static and warp breakage, whereas rapier sheds operate in drier environments.

Oven-dry mass provides the reference point. Weighing raw greige fabric straight off the loom without conditioning creates immediate pricing errors: a roll weighed in a humid shed registers heavy, then loses several percent of its weight after twelve hours in a dry shipping container. Finding the true mass loss requires measuring the oven-dry mass of the grey fabric first, then applying the official commercial moisture regain factor set out in ISO 2060.

Ambient moisture variations across storage locations alter measured greige mass without changing the physical fibre content.

The standard commercial moisture regain for 100% flax yarn is 12.0 percent. To determine standard commercial mass, gross off-loom weight is converted to oven-dry mass before adding the standard regain allowance back in. For example, if a greige roll weighs 150.0 kilograms off the loom with a measured moisture content of 15.5 percent, its oven-dry mass is 129.87 kilograms.

Adding the standard twelve percent regain gives a corrected commercial mass of 145.45 kilograms.

Failing to separate moisture regain from actual fibre loss skews the cost structure. A buyer who accepts unconditioned off-loom weights as a baseline overpays for water. Then, when wet processing removes non-cellulosic material, the mill can attribute that missing water weight to chemical extraction, masking excessive yarn shedding or damage in the boil-off bath.

Sizing

Warp yarns need protective coatings to endure the tension and abrasion of high-speed shedding. Linen sizing agents typically rely on modified starches, carboxymethyl cellulose, polyvinyl alcohol, and tallow lubricants. Because weft yarns are not sized, the overall size percentage in greige fabric depends directly on the warp-to-weft ratio determined by the draft.

Which Testing Standards Govern Greige Mass Calculation?

Measuring warp size pick-up involves desizing swatches according to ISO 7211-3, expressing dry size weight as a percentage of dry un-sized yarn mass. High-speed rapier looms typically require size pick-up levels between five and eight percent on single flax warps. Air-jet looms need film-forming compounds to prevent filamentation, which increases total pick-up, whereas heavier yarns generally require less size overall.

Abrasion during weaving generates shed fly ~ short flax fibres, flakes of dried size, and surface fuzz that fall beneath the harness frames during beat-up. This fly waste reduces the net dry mass leaving the loom beam by 0.5 to 1.6 percent, removing weight before final inspection.

• Un-sized weft proportion lowers the overall fabric size percentage, as only warp strands receive sizing during slasher preparation.
• Shed fly droppings collect under reed assemblies, representing lost yarn weight that never reaches the cloth roll.
• Cold baths leave sizing intact during basic rinses, requiring enzymatic or oxidative desizing for full removal.
• Polyvinyl alcohol additives resist standard hot washing and require thermal desizing above eighty-five degrees Celsius.

Attributing a six percent mass drop solely to natural pectin removal often masks incomplete size reporting. Unreported high size pick-up disguises low yarn quality by inflating off-loom mass per square metre.

Boil

Alkaline scouring removes non-cellulosic components from raw flax during wet processing. In addition to cellulose, raw flax contains hemicellulose, pectin, lignin, natural waxes, and mineral salts. Dew-retted flax carries a higher proportion of these non-cellulosic materials ~ and retains more lignin ~ than water-retted flax, leading to greater mass reduction when pectin dissolves during boil-off.

Quantifying Chemical Extraction during Scouring

Scouring with sodium hydroxide at high temperatures saponifies natural fats and hydrolyzes pectins. Total mass loss during thorough boil-off and bleaching runs between twelve and twenty-two percent of the dry grey fibre weight. Fully bleached white linens experience the highest weight loss, whereas semi-bleached or boiled linens retain some residual lignin.

A 1000-metre lot of dew-retted grey linen fabric yields an average net dry mass loss of 18.8 percent after complete enzymatic desizing and alkaline scouring.

Consider a commercial production batch of 1,000 linear metres of plain weave linen at a greige width of 160 centimetres. With an off-loom weight of 215 grams per square metre, total gross weight off the loom is 344.0 kilograms. At a measured moisture content of 14.5 percent, the calculated oven-dry mass of the lot comes to 300.44 kilograms.

Laboratory tests confirm a dry warp size pick-up of 6.0 percent on a warp making up 53 percent of total dry fabric mass, giving 9.01 kilograms of total size across the lot. Removing size leaves 291.43 kilograms of dry grey fibre. With scouring and bleaching tests showing a 14.5 percent extraction loss of non-cellulosic material for this yarn blend, 249.17 kilograms of net dry fibre remain after boil-off.

Reconditioning the finished fabric to the standard twelve percent moisture regain brings final commercial weight to 279.07 kilograms. Comparing the initial gross off-loom weight of 344.0 kilograms to this conditioned finish weight shows an absolute loss of 64.93 kilograms, or an overall weight reduction of 18.88 percent from loom to bolt.

Standard contract specifications following ISO 3801 require mass loss calculations to rely on oven-dry mass adjusted for commercial regain, rather than raw, unconditioned roll weights.

Shrinkage

Contraction during wet processing alters fabric density per unit area even as total mass drops. As warp and weft crimp relax during desizing and scouring, linear shrinkage increases mass per square metre ~ particularly in plain weaves with high crimp ~ even while overall roll weight declines and finished width determines final running weight.

Determining true material loss requires separating linear dimensional contraction from mass extraction. When a plain weave linen shrinks ten percent in length and five percent in width, its remaining fibre is packed into a smaller surface area ~ meaning weight per square metre can appear unchanged even after an eighteen percent drop in overall batch mass.

1. Cut three representative 500 millimetre by 500 millimetre swatches from the greige roll, keeping clear of the selvedges.
2. Weigh the swatches on a calibrated balance to 0.01 grams, recording baseline weight and dimensions.
3. Desize the swatches in an enzymatic bath at sixty degrees Celsius for thirty minutes to remove warp sizing completely.
4. Scour the swatches in a sodium hydroxide bath at ninety-five degrees Celsius for sixty minutes, rinse thoroughly, and dry to constant mass in an oven at one hundred five degrees.

The interaction between weft tension adjustments and scouring contraction leaves little doubt that contract specifications must include clear allowances for absolute mass loss.

Reconciliation

Commercial settlements for linen grey goods require clear mass correction formulas in buying contracts. Procurement schedules for raw yarn must account for cumulative processing losses: ordering 1,000 kilograms of raw yarn yields roughly 810 kilograms of finished fabric once shedding fly, size removal, and boil-off extraction are accounted for. Because yarn contracts rely on gross weight while loom scheduling covers target linear metres, inspecting greige goods prior to wet processing is essential.

Purchase orders that set grey fabric weight targets without specifying moisture and sizing limits expose buyers to unrecoverable yield shortfalls.

Allocating loom capacity depends on realistic finished weight projections. When a mill schedules production, it sets reed width and pick density around target fabric weight; underestimating non-cellulosic mass loss forces adjustments to warp or weft density, raising picks per metre and expanding the loom hours needed per batch.

• Standard moisture regain terms establish twelve percent as the mandatory baseline for grey linen trade invoicing.
• Maximum size add-on limits restrict warp sizing content to seven percent of dry warp yarn mass in greige purchase orders.
• Scouring extraction allowances define acceptable mass loss ranges based on retting method and target finish.
• Tolerances on grey GSM hold weight variations within plus or minus five percent of specification sheets.

Reconciling grey linen invoices requires converting raw off-loom roll weights to dry fibre mass before applying standard regain allowances. Contracts that base price on oven-dry mass adjusted for commercial regain eliminate disputes over shed humidity, size padding, and variable boil-off losses.