Sei Pillowcase Pair

The Sei Pillowcase Pair is 100% cotton in a sateen weave at 600 thread count, garment-washed after construction. Sei is MATTEO's highest thread count fabric, woven with the same 120/2 Ne yarn in both warp and weft for a balanced, silky hand that holds up wash after wash. The sateen construction gives the face a soft, smooth finish while the garment-washing process removes any initial stiffness before the pillowcase reaches you.

Thread count measures the density of the weave — the number of yarns per square inch — but it does not account for yarn quality, fiber length, or weave balance. At MATTEO, we stopped at 600 TC because counts above that typically produce a fabric too dense to move or breathe. Sei at 600 TC hits the point where density translates to softness without sacrificing drape, which is why it remains one of our most requested fabrics for luxury cotton pillowcases.

The Sei Pillowcase Pair is available in Queen (20 x 33 inches / 51 x 84 cm) and King (20 x 39 inches / 51 x 99 cm). MATTEO does not offer a Standard size pillowcase; we recommend using the Queen pillowcase with a Standard pillow insert — it will extend slightly beyond the insert and can be tucked in for a cleaner finish, or taken to a seamstress for a simple alteration.

Pillowcases loosely encase the pillow insert and are open on one side; shams are more fitted and use a closure — a zipper, envelope flap, or ties — to keep the pillow in place. The Sei Pillowcase Pair is an open-sided pillowcase finished with a half-inch hem and a double-stitch detail. Darker colorways also carry a contrasting white topstitch, which adds a clean visual detail without adding bulk.

Wash light and dark colors separately in a lukewarm cycle with a gentle detergent and a cool rinse; do not overload the machine, as excess friction damages the long cotton fibers. Tumble dry on low heat and remove promptly to reduce wrinkling — line drying gives the best result. Because Sei is garment-dyed using reactive dyes, avoid chlorine bleach, alpha hydroxy acids, and benzoyl peroxide on any colored pillowcase; bleach is safe only on white cotton. For a pressed look, iron while slightly damp on the Lightweight Cotton or Medium setting.

Sei pillowcases are made from 100% cotton with no synthetic fiber content, and all dyeing uses non-toxic reactive dyes. The garment-washing process eliminates residual finishing agents before the pillowcase ships, so the fabric arrives with a broken-in softness rather than the stiffness common in unwashed sateen. Cotton at this yarn quality and weave density is a straightforward choice for sleepers who prefer natural fibers against their skin.

The Sei Pillowcase Pair is built for exactly the kind of bed where construction detail matters at close range. The half-inch hem with double-stitch finish and the contrasting topstitch on darker colors are the same tailoring choices found in hotel-grade white bedding, applied here across a broader color range. Pair the pillowcases with the Sei Sheet Set for a cohesive 600 thread count cotton sateen bed — the fabric weight and drape read as hotel-quality without requiring white-only colorways.

Garment-dyeing is an artisanal process, and MATTEO allows for a shade variation of +/- 10% between dye lots. If you are ordering multiple pairs at once — or adding to an existing set — ordering together reduces the chance of visible tonal differences. This is an inherent characteristic of reactive garment-dyeing, not a defect, and is part of what gives each piece a lived-in, hand-finished quality.