The process of pre-shrinking a fabric so to a limit the residual or further shrinkage of the fabric to less than 1%. This sanforization process involves the stretching of the fabric before it is washed, which helps to prevent shrinkage. Fabric that doesn’t undergo sanforization and is considered raw is likely to shrink up to 10% on the initial wash and continue to shrink up until the third wash. In the world of denim, un-sanforized denim is referred to as raw denim.
Sanforization is a process that stabilizes the fabric before it is cut by stretching and shrinking it. Named after its inventor, Sanford Lockwood Cluett, it was patented in 1930. In 1936, Blue Bell (now Wrangler) began using the method for its Super Big Ben overalls. During the sanforization process, the material is fed into a sanforizing machine and moistened with water or steam to promote shrinkage. It is then stretched through a series of rubber belts and cylinders before it is finally compacted to its final size. Sanforizing ensures that the fabric will not shrink during production or wear.
Here is an example of the sanforization process:
Here is the sanforization machine process: