How do you tell the difference between silk and satin?

You can tell the difference between silk and satin by understanding that one is a fiber and one is a weave, and then using several practical tests. First, check the label. If it says 100% silk, it is silk, and if it is woven in a glossy weave, it may be called silk satin. If it says 100% polyester and satin, it is not silk, it is imitation silk. Second, look at the shine. Real silk satin has a soft, deep, pearly luster that changes subtly in the light, while polyester satin has a harsh, bright, almost plastic-like shine. Third, feel the fabric. Silk feels warm, soft, and smooth with a natural texture, while polyester satin feels cool, slippery, and sometimes almost plasticky and can generate static. Fourth, check the back. Satin weave has a shiny front and dull back regardless of fiber, but silk charmeuse drapes like liquid and wrinkles easily, while polyester satin is stiffer and more wrinkle-resistant. Fifth, the burn test if you have a spare thread. Silk smells like burnt hair and turns to ash, polyester melts and smells like plastic and forms a hard bead. Finally, price is a strong clue. Real silk satin is significantly more expensive than polyester satin.