Two silk pillowcases sit on the same shelf at wildly different prices, both labelled “100% silk.” The cheaper one will pill and fade within months. The expensive one could last years. Here’s what the labels deliberately leave out.
Two pillowcases, both labelled "100% silk," sitting at very different price points on the same shelf - and neither label explains why. The answer lies not in the fabric's purity, but in the fibre beneath it: how long it is, how consistent, and which silkworm produced it. That distinction separates a purchase that lasts years from one that loses its sheen by spring.
"100% silk" is a compositional claim, not a quality guarantee. It confirms the fabric has not been blended with polyester or another synthetic - and that is essentially where its usefulness ends. The label does not specify whether the silk comes from Bombyx mori silkworms fed primarily on mulberry leaves, or from wild species like tussar or eri moths that spin under entirely different conditions. It does not state the fibre length, the diameter, the weave weight, or the processing grade. Two products wearing identical labels can differ enormously in softness, durability, and long-term value.
For shoppers buying bedding, pillowcases, or anything worn against skin regularly, that omission matters. Wild silks and Mulberry silk are both technically 100% silk, but they behave very differently over months of use.
Mulberry silk comes from Bombyx mori silkworms raised in controlled conditions, primarily on mulberry leaves, though they can consume other plants with less nutritional benefit. That controlled diet and environment produce a fibre with two characteristics that separate it from wild alternatives - extraordinary length and exceptional diameter consistency.
Each Bombyx mori cocoon contains a single continuous filament that can extend anywhere from 900 to 1,500 metres. Because the thread is unbroken, it can be reeled - unwound in one long strand rather than cut or pulled apart. Reeling preserves the filament's tensile integrity, which is why Mulberry silk fabric resists tearing and snagging far better than fabrics built from shorter, spun fibres. Several thousand cocoons are combined to produce just one pound of finished silk, which signals immediately why the raw material commands a premium.
Mulberry silk fibres typically measure 12-19 microns in diameter - fine enough to feel soft against the skin while remaining strong enough to hold a weave under repeated washing. What matters as much as the measurement itself is the consistency: fibre after fibre runs to the same specification, producing a uniform surface with no rough patches or uneven slubs. Consistent fibre diameters deliver predictable performance across the full length of the cloth, resulting in a smoother, softer hand and reduced susceptibility to wrinkling or breakage over time.
Wild silks - tussar, eri, muga - are genuine silk, and each has properties worth knowing. They are not produced under the same controlled conditions, however, and the fibres reflect that.
Wild silk fibres typically measure 20-30 microns in diameter, roughly double the fineness of Mulberry silk, and their filaments are considerably shorter and less consistent in length. Because the threads cannot be reeled into one continuous strand, they must be spun - a process that cuts or breaks the fibre and joins the pieces together. Spun fibres create a slightly textured, less fluid fabric with a coarser surface feel and a less luminous drape compared to the smooth, lustrous cloth Mulberry silk produces.
Wild silks also present practical challenges during and after production. The natural irregularities of wild silk fibres can make consistent dyeing more challenging, potentially limiting colour options and leading to uneven uptake compared to the uniform nature of Mulberry silk. Some varieties of wild silk may shrink when exposed to warm water and require specific handling throughout their lifespan. For furnishing fabrics or statement fashion pieces where texture is part of the aesthetic, wild silk's natural slubs can be desirable. For skin-contact bedding washed regularly, those same characteristics become liabilities.
Mulberry silk fabric typically costs $30-$120 per metre against $20-$80 for wild silks at a comparable weight. The gap reflects fibre structure paying a dividend across the lifespan of the product.
Pilling occurs when short, loose fibres tangle and form small knots on the fabric surface. Mulberry silk's long, continuous filaments have no short ends to work loose, which is why the fabric holds its smooth surface through repeated wash cycles that would leave a spun-fibre fabric visibly degraded. The tensile strength that comes from unbroken filaments also resists snagging - a practical concern for anything slept on nightly.
Mulberry silk's naturally pure white base - a direct result of the Bombyx mori diet - accepts dye evenly and predictably. The result is richer, more stable colour that does not shift or fade unevenly after washing. That same fibre uniformity maintains softness: with no short fibres stiffening or breaking at the surface, the hand of the fabric after fifty washes feels closer to the hand on day one than any wild silk equivalent can reliably deliver.
Fibre type explains quality; momme weight explains durability. Momme (mm) is a Japanese unit measuring the weight and density of silk fabric - the higher the number, the more silk is packed into each square metre of cloth.
Most silk bedding sold under a generic "100% silk" label is woven at 19 momme - a weight that is light, smooth, and passable for occasional use. At 22-25 momme, the fabric is noticeably thicker, more resistant to tearing and snagging, and significantly more durable across sustained nightly use. Research into silk durability consistently shows that higher momme counts correlate with longer fabric lifespan; 25 momme silk bedding demonstrates substantially higher resistance to snagging compared to 19 momme alternatives. Mayfairsilk weaves its sheets at 22 momme and its pillowcases at 25 momme - both above the 19 momme standard that most "100% silk" bedding uses.
Silk grading typically runs from Grade C (lowest) to Grade A (highest), with Grade 6A representing the highest quality within the A grade, assessing fibre length, uniformity, purity, and tensile strength. Grade 6A Mulberry silk sits at the top of that scale - distinguished by the longest, most uniform, and structurally strongest fibres available in commercial silk production. It is the grade used in premium bedding and high-end apparel precisely because it combines softness with longevity in a way no lower grade reliably replicates.
Most "100% silk" products on the market do not state a grade at all. That silence is itself informative. Products that achieve Grade 6A tend to say so clearly, because the specification justifies the price. If a label omits the grade, it is worth asking why.
For silk that genuinely delivers on its promises - softness that lasts, colour that holds, a surface that survives the wash cycle - the specification combination to look for is Grade 6A Mulberry silk at 22 momme or above. That combination addresses every variable the "100% silk" label leaves open: fibre source, fibre quality, and fabric density.
A price that seems unusually low for Mulberry silk at this grade is a reliable indicator that the product is either a lower-grade Mulberry, a wild silk variety, or a blend - any of which will perform differently to what the label implies. Genuine Grade 6A at meaningful momme weight is not cheap to produce, and products priced as though it were should be scrutinised carefully.
For anyone investing in silk bedding, the upgrade from generic "100% silk" to Grade 6A Mulberry at 25 momme is the difference between a fabric that looks good on arrival and one that earns its place on the bed for years.
