Anyone who works around original Victorian/Edwardian Era clothing for any length of time will inevitably encounter the phenomenon of shattered silk. To the naked eye, the silk fabric appears to be literally splitting apart or “shattering” into strips. In extreme cases, the silk will literally turn to dust with even the slightest of handling.
Silk was one of the primary fabrics utilized in garments of these eras and this is especially true for women’s. For anyone who collects or just simply admires clothing of this era, it can be heart-rending, especially since there is no way to reverse the process once it starts. Below is just one example of shattered silk; note how the fabric is splitting or shredding into its constituent yarns.
So what exactly IS “shattered silk”?
Well, the simple answer is that shattered silk is when the silk fibers have broken down to the point where it affects the structure of the silk fabric thus creating a shattered or shredded appearance. This is a condition that worsens over time and the silk fibers are literally decomposing. Eventually they become so fragile that the fibers/fabric literally turns to dust with the slightest of handling.
So what causes this? The short answer is that it is due to the use of weighting agents that have been added as a finish to the newly-woven silk fabric. Over time, the chemicals in the weighting agents cause the structure of the silk fibers (or more properly, filaments) to decompose (i.e. breakdown). Combined with poor storage practices and exposure to dirt and light, it’s only a matter of time before those beautiful silk garments turn to a pile of scraps or even dust.
That’s the short answer. However, there are some technical aspects that need to be considered (don’t worry, we’re not going to get into chemical analysis and the like :-)). To begin with, consideration must be given to silk itself.
Silk is a natural protein fiber that make up the cocoons produced by silkworm larvae. Some of the the most widely utilized species of silkworms are: Bombyx mori (Mulberry Silkworm), Hyalophora cecropia,Antheraea pernyi, and Samia cynthia. The fiber making up the cocoon is mainly composed of the proteins, sericin and fibroin. Production of the cocoon is part of the process where the silkworm is undergoing a metamorphosis into a moth.
The cocoons are then harvested and treated with hot air, steam, or boiling water. The silk is then unbound from the cocoon by softening the sericin and then delicately and carefully unwinding, or ‘reeling’ the filaments from four to eight cocoons at once, sometimes with a slight twist, to create a single strand. The boiling process also kills the larva before it can transform into a moth which in turn preserves the cocoon in its whole form; it is desirable to prevent the moth from hatching since this preserves the structure of the cocoon and allows the silk fiber to be unreeled from the cocoon in a continuous filament (versus a series of broken filaments). A continuous filament is more is desirable because it is easier to spin into thread and yarn.
The sericin protects the silk fiber during processing and this is often left in until the yarn or even woven fabric stage. Raw silk is silk that still contains sericin. Once this is washed out in soap and boiling water (the “degumming” process), the resulting fabric is left soft, lustrous, and up to 30% lighter. The amount of usable silk in each cocoon is small, and about 2500 silkworms are required to produce a pound of raw silk. On the average, a single cocoon contains 1000 yards of silk filament.
By now you are probably asking “So that does this have to do with shattered silk?” Well, the important part to keep in mind is the sericin. Normally, this acts as a protective coating but it ultimately must be removed through degumming if the silk filament/yarns are to have the most optimal effect when the fabric is woven. Unfortunately, as a result of degumming, the silk would lose 25% to 30% of its starting weight. While that may not make much of a difference for many silk applications, it made a big difference for making larger garments such as dresses in that the drapability, or the manner in which a fabric falls or hangs over a three dimensional object (e.g., a person), was adversely affected. And more importantly to the silk manufacturer, the silk had lost value since silk was sold by weight.
To make up for the loss, manufacturers hit on the idea of weighting the silk fabric. The weighting of fabrics has been a long-standing practice and a variety of materials were employed but this was meant primarily as a means of enhancing a fabric’s drapability. Turning to the 19th Century, metallic salts themselves, lead, iron, and tin were found to be the most effective. In particular, Tin Chloride or Stannous Chloride was especially favored and was used both as a mordant for dyeing and by itself as a weighting agent (mordants are mineral salts that bind dyes into fiber).
In order to restore and enhance silk’s drapability and the maintain the manufacturer’s profit margin, the silk fabric was weighted with metallic salts during the finishing process. Silk has a natural affinity for metallic salts, having a tremendous capacity for absorbing dyes and salts without superficially changing the quality of the material. It didn’t take too long for manufacturers to realize that profits could be easily enhanced by adding salts and dye that would increase a given quantity of silk fabric some 200% to 300%.
However, weighting with metallic salts came at a price in that while it improved drapability and enhanced dye colors, it also greatly reduced the strength and durability of the silk filament fabric. The end result was a silk fabric that had poor durability and it was a problem that was even widely recognized in the 19th Century:
Look at it how we will, the weighting of silks
is a nefarious practice which should be forbidden
by law. It causes a black silk dress to become
more or less shabby in a single twelvemonth.
Interestingly enough, not only was weighted silk considered to be dishonest, but also inherently dangerous:
Black silks which have been weighted to the
extent of 300 or 400 per cent. have been known
to take fire of their own accord-that is, without
the contact of a substance in ignition. Not
many years ago a fire broke out in the warehouse
of a large silk-mercer in Paris, and was
traced to this cause. It was found to have
originated inside a large parcel of black silk,
which had been delivered only twenty-four hours
previously from the dyers. In 1871 a fire traced to
a similar cause occurred in a silk-dyeing establishment
in the United States. It is now considered
unsafe to pack such weighted silks in deep boxes.
The above quotations are from Chamber’s Journal, Volume I, December 1897 – November 1898.
In terms of collecting and preservation, the use of metallic salts has greatly accelerated the deterioration process through the loss of tensile strength of the silk filaments themselves ultimately resulting in rupturing. Also, it must be noted that this comes on top of deterioration due to exposure to light and dirt.
Below are some examples of shattered silk as found today with garments from the late 19th Century:
What is is especially interesting in the above examples is that the majority of the shattering in in the sleeves and it follows a cross-grain direction. This would suggest that the warp yarns have deteriorated first, perhaps because warp yarns have greater tension.
Shattered silk is an historical curiosity and as such a consequence of a particular method of silk fabric finishing that was employed mostly in the late 19th and early 20th Centuries. Today, the use of metallic salts to weight silk fabric is regulated by the Federal Trade Commission which issued a regulation in 1932 specifying that ruled that any product labeled pure silk or pure dyed silk could contain no more than 15% weighting if black and no more than 10% weighting for other colors. Also, thankfully, weighted silk is no longer commonly found in the US market, the result of the development of improved dyes plus increasing concerns over health and environmental effects.