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The Sanforized Process
Most men and women have purchased that - perfect garment - only to find the collar too tight and the sleeves too short after the garment is laundered. When this occurs, the first thought which comes to mind is "How could this have happened?".
During spinning, weaving, bleaching, dyeing and the various finishing processes, yarns and cloth are under a continuous lengthwise tension.
During the spinning process, the yarn is wound on a bobbin under high tension. Even during the processes prior to spinning, such as carding and combing, there is tension on the fibres.
Weaving, the process of forming a fabric on a loom by interlacing the warp (lengthwise yarns) and the filling (crosswise yarns) so that they cross each other at right angles, requires a very high tension on the warp yarns.
As the shrinkage of the garment occurs during laundering, it would be expected that the before mentioned tensions within the fabric would be eliminated during the various stages of the wet processes. However, this is not the case since the woven fabrics pass every stage of the production process under a lengthwise tension. The fabric does not shrink, but continues to stretch.
Yarns and/or fabrics are not fixed materials, but consists 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 are 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 lubricants, along with the mechanical action of the washer help the fibres relax and contract to their original length before the elongation takes place. This means that fabric shrinks and recaptures its original equilibrium.
Controlled compressive shrinking
The internationally well-know and most important shrinking process today dates back more than 50 years. Though the correct expression for this process is Controlled Compressive Shrinkage, the man on the street knows it as SANFORIZED. The process is purely mechanical treatment without any addition of chemicals.
The word SANFORIZED is derived from the first name of the inventor of the compressive shrinkage process, Mr. Sanford L. Cluett.
The Sanforized Company, a division of Cluett Peabody & Co., in New York, U.S.A. is sole owner of the registered trade marks: SANFORIZED, SANFOR and SANFORIZADO.
Sanforized means that fabrics which carry the famous Sanforized label are tested according to the severe test methods required by the owner of the trade mark. These fabrics will not shrink more than 1% (Sanforized Standard) in either warp or weft.
The Sanforized label means dimensional stability for garments made up of Sanforized labeled fabrics.
The purpose of the process is to shrink fabrics in such a way that garments made up of these fabrics do not shrink during washing. The amount of potential wash shrinkage must be determined prior to shrinking. A full width sample is wash tested according to the Federal Specification - CCC-T-191a-wash test method. A copy of this method may be obtained from Sanforized Service offices throughout the world. After the lengthwise and widthwise shrinkage has been determined, the compressive shrinkage machine can be adjusted accordingly.
The process which was developed, introduced and promoted by Cluett Peabody & Co., New York, U.S.A. can be described as follows:
Fabric (F) passes through the skyer (S) or other moistening device and is moistened by water and/or steam. This will lubricate the fibres and promote shrinkability within the fabric. Normally, a fabric must be moistened in such a way that every single thread achieves a moisture content of 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 transports the fabric to the most important part of the machine: The rubber belt unit (indicated by arrow in above figure). In the close-up of fig. I, 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 shortening of the warp yarns which packs the filling yarns closer together. At this actual moment, shrinkage occurs.
After compaction within the rubber belt unit, the fabric enters the dreyer. Here the fibres 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 washed according to the before mentioned CCC-T-191a wash test method. The final results of this test must meet the Sanforized Standard, i. e. a gain or loss of no more than 1% (plus or minus) in either length or width before it may carry the Sanforized label.
In principle, the objective is to always obtain a ± 0%. The 1% tolerance is however necessary since woven fabrics tend to be somewhat elastic and not rigid like wood or steel.
All Sanforized Licensees are contractually obligated to follow the required test method and meet the standards set forth by the Sanforized Company.
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