Sanforizing

The term Sanforized, is their registered trademark and is used to market fabrics that meet certain shrinkage specifications. The term Sanforized is now generally accepted to mean a fabric that has low residual shrinkage and the term Sanforizing is used to describe shrink proofing processes. While the patents on the machinery have expired, the trademark is actively promoted by Cluett Peabody. The effect of Sanforizing can be seen in figure 68 which shows that open fabric structure has been closed up somewhat.

What Causes Shrinkage

During spinning, weaving, bleaching, dyeing and the various finishing processes, yarns and cloth are under a continuous tension. Yarns and/or fabrics are not fixed materials. They consist of separate, stretchable fibers which submit to the tension. In other words, fabrics do stretch in length and width. The tension within the yarns, which is caused by this stretching, can be eliminated when the friction within the fabric is reduced. This reduction in friction occurs during laundering where both water and Soap act as a lubricant. The lubricant, along with the mechanical action of the washer, helps the fibers relax and contract to their original length before the elongation takes place. This means that the fabric shrinks and recaptures its original equilibrium.

Sanforizing Process

The process can be described by the schematic below. Fabric (F) passes through the skyer (S) or other moisten-ing device and is moistened by water and/or steam. This will lubricate the fibers and promote shrinkability within the fabric. Normally, a fabric must be moistened in such way that every single thread achieves a moisture contentof approximately 15%. This allows compression of the fabric with very little resistance. When the fabric passes through the clip expander (C), we obtain the required width. The clip expander also trans-ports the fabric to the most important part of the machine: the rubber belt unit (indicated by arrows in above figure). In the close-up of fig. 1, we see the endless rubber belt (R). By squeezing rubber belt (R) between pressure roll (P) and rubber belt cylinder (RB) ,we obtain an elastical stretching of the rubber belt surface. The more we squeeze the rubber belt, the more the surface is stretched. This point of squeezing is known as the pressure zone, or the nip point. Fabric (F) is now fed into the pressure zone. 

 

 

 

 

When leaving the pressure zone, the rubber belt recovers itself and the surface returns to its original length carrying the fabric with it. The effect of this action is a shorting of the warp yarn which packs the filling yarns closer together. At this actual moment, shrinkage occurs. After compaction within the rubber belt unit, the fabric enters the dryer  (D) . Here the fibers are locked in their shrunken state by removing the moisture from the fabric. After the compressive shrinkage process is completed, another sample of the fabric is taken. This sample is also wash-tested. The final result of this test must meet the Sanforized Standard in length and width before it may carry the Sanforized label. All Sanforized Licensees are contractually obligated to follow the required test method and meet the standards set forth by The Sanforized Company.