Satin is one of the basic weaves, along with plain and twill. The warp yarns in a satin weave cover the weft yarns as much as possible (less common is the opposite where weft covers warp). This creates a lustrous surface. The pattern is most often 4/1 but can also be 7/1 or 11/1. In these patterns, warp yarns float over weft yarns in numbers of 4 to 1, 7 to 1 and 11 to 1, and the interlacings do not occur in rows, giving the most uninterrupted gloss possible. Here's the anatomy of a 4/1 satin weave. See how four weft yarns are crossed by a warp yarn? And how the weft crossings are staggered? Here is a close up of silk satin: And of course we all know the look of satin from this type of glossiness: So satin is the name of one of the basic weaves, but it is also a fabric made in this weave. Judging from looking around eBay and Etsy, a number people seem to conflate satin and silk, saying something like it is silk because it is satin. This is an understandable mistake, with silk being a smooth fiber and the original and most attractive fiber for satin, and satin having a silky feel. Staple and filament fibers Of the two fiber types, staple and filament, filament is the long one, often measuring hundreds of yards in length. Silk is the only natural filament fiber, but manufactured fibers always start as very long fibers and can be cut as needed. Filament fibers make smooth, strong yarns, the kind necessary for satin. Filaments made of manufactured fibers such as acetate and rayon can make a satin, and, because they are less expensive than silk, have often been used. A great majority of lower- to mid-priced vintage garments made of satin are not silk. Remember a few weeks back when I suggested that you start with a suspicion about the fiber before doing a thread-burn test? If you have a higher-end vintage item that is satin, you might start by suspecting it to be silk. The average satin prom dress from the 50s? Start with the suspicion that it's manufactured fiber (often acetate or rayon). There are a number of types of satin, and not all of them have made their way into the Fabric Resource (yet!). Here is duchesse satin close up. It is a heavy and luxurious very lustrous satin made of fine filament yarns in a tight satin weave. Originally always silk, duchesse can be rayon, polyester or acetate. Uses: Evening gowns, bridal One great place to find examples of garments with their fabrics properly named is in museum collections. Look up "duchesse satin" in The Met collection and you find this Irving Penn photo of a Christian Lacroix dress (1995). You can just feel the weight and luxury of this fabric!— The V&A is also a great resource. A search for duchesse satin in their collections came up with this Norman Hartnell dress that Queen Elizabeth wore for a state visit to Paris in 1957— You can not just suspect, but be sure that this example of duchesse is silk fiber because of the dress's importance. Another satin fabric type is crepe-back satin. Lustrous on one side and with a crepe texture on the other, this light to medium weight fabric is called crepe-back satin when its glossy side is its face, and satin-back crepe when the dull side is the face. It can be called crepe satin or satin crepe as well. Sometimes the contrasting sides of the fabric are both used on the outside of a garment. Characteristically silk, it can be made of rayon or manufactured filament fibers. Uses: Blouses, dresses, evening gowns, lining When I find crepe-back satin used for a vintage garment, that item most often has dated from the 1920s or 1930s. It is a wonderfully substantial and fine fabric. This close up of rayon crepe-back satin shows the satin face on the left, the crepe reverse on the right, with the selvage in the middle. Crepe-back satin gives a good opportunity to say that looking at the reverse of fabrics (if at all possible in a garment) is a very good practice. The reverse often is the giveaway as to the fabric type, sometimes in combination with the face. This is an example of a 1930s dress made of silk crepe-back satin using both sides of the fabric. It was sold by RP vintage. Another small issue with satin is the spelling: Satan does not get its spelling corrected by spell checkers, and pretty vintage ‘satan’ dresses show up regularly on eBay and Etsy! Questions and comments please!