Direct answer: Real silk breathes, regulates temperature, and feels cool and dry against skin, but costs far more and wants gentle washing. Faux silk, usually polyester satin, matches the shine, survives the machine, and costs a fraction, while sleeping warmer and building static. Choose silk for pillowcases and next to skin pieces you will keep for years, faux for washable, high turnover items.
Few fabric comparisons are as lopsided in the marketing as silk versus its imitators. The faux version borrows the shine, photographs beautifully, and arrives at a tenth of the price, so the real thing can look like a luxury tax. Spend a summer night in both, though, and the fabrics stop pretending to be twins: they manage heat, moisture, and friction very differently.
This comparison goes property by property, shine, temperature, skin and hair friction, care, durability, and cost, and ends with a simple rule for which fabric deserves which job. Neither wins outright; each wins the uses it is actually suited to.
Real silk's shine is depth, not glare: the triangular fiber reflects light softly and unevenly, so the fabric glows rather than flashes. Polyester satin is shinier in the cheap sense, a flat, uniform gloss that reads synthetic under daylight and camera flash. In hand, silk feels cool and almost dry, sliding without clinging, while polyester satin feels warmer, slicker, and prone to static crackle in dry rooms.
Temperature is where the gap becomes functional. Silk breathes and buffers moisture, taking up perspiration without feeling wet, which is why it has been sleepwear for centuries. Polyester traps heat and humidity against the skin, so faux silk pajamas and pillowcases run warm on summer nights and can feel clammy by morning. For a scarf in winter the warmth hardly matters; for anything slept in, it matters a lot.
The hair and skin case for silk pillowcases is friction: a smooth surface lets hair glide instead of snagging, reducing breakage and morning frizz. Polyester satin is also smooth, honestly nearly as slippery, so the budget pillowcase delivers much of this benefit. Where it loses is the warm, static prone sleep surface, and a tendency to pill and dull as the satin face abrades over a year or two of washing.
Care runs the other way. Real silk asks for cool water, gentle detergent, and air drying, and resents sweat, perfume, and sunlight, all of which weaken it. Polyester satin goes in the machine with the regular wash and comes out unwrinkled and unchanged. Cost completes the picture: real silk pillowcases and garments cost several times the faux equivalent, so the silk purchase only pays off where its properties are used nightly and the item is kept for years.
Buy real silk where skin contact is long and the item is durable in your life: the pillowcase, the sleep set you will actually hand wash, the scarf that lives against your neck. Buy faux silk where washing is frequent, loss is likely, or the shine is the whole point: travel sets, guest bedding, costume and event pieces, and linings where breathability barely matters.
One caution on labels: much of what is sold as silk in budget listings is polyester with the fiber content in small print, and some is a silk blend with a minority of real fiber. Check the fiber content line, not the product title, and treat momme weight as the silk quality signal, with higher momme meaning denser, longer lasting fabric.
Readers working through this topic often find these earlier guides useful as well: Vegan Leather Labels Explained: Plant Based, Bio Based and PU, Plant Based Leathers Explained: Cactus, Mushroom, Apple, and Pineapple Materials.
For friction alone, nearly: polyester satin is smooth enough to cut snagging and frizz for most hair types. The differences are heat, static, and how long the smooth surface lasts before pilling.
Momme is silk's weight measure: higher momme means a denser weave with more silk per area, generally smoother and more durable. Pillowcases commonly range from 19 to 25 momme, with the upper end lasting longer.
Many modern silk items survive a gentle cold cycle in a mesh bag, but hand washing remains the safest route and the one makers recommend. Heat and harsh detergent do most of the damage attributed to machines.
Polyester does not absorb moisture, so charge has nowhere to dissipate, especially in dry heated rooms. Real silk's moisture uptake bleeds charge away, which is why it clings and crackles far less.