Weighted silk
Encyclopedia
The process of "weighting" silk
fabric is the addition of metallic salts during processing for the purpose of increasing the weight of the finished goods.
Unlike most fabric/yard goods which are sold by the yard (or metre), silk is sold to the wholesaler by weight. The first step in processing the silk fiber is "degumming the fibre," the gum being a byproduct of the production of the silk fibre by the worm. Approximately one-fifth of the weight of the silk fibre is lost in the degumming process, and manufacturers felt they had the "right" to replace this lost weight with a filler of some sort. Silk has an affinity for several metallic salts, the most common of which being iron, lead, and tin. It was discovered to be an easy process to return this weight lost in the degumming process by soaking the fibre in a bath of these metallic salts. This process was called weighting, and by increasing the weight of the raw silk, the merchant increased his profit. Weighting with some metallic salts did improve the drapeability of the fibre; however greedy merchants soon began adding more weight than the lost one-fifth; sometimes the final weight was increased tenfold.
While silk is a strong and durable fibre, the weighting process is highly damaging to the finished goods. If the garment is worn, it wears out quickly and is highly susceptible to perspiration, salt, and tears; if stored away it becomes brittle and breaks. The method of storage--cold/dark, etc., has no influence on these factors. One readily sees examples of this damage in antique American "Crazy Quilts" where the silk fibres have disintegrated while the cotton and wool fibres remain in good condition, even after 100 years.
This practice was widespread in the 19th century and decreased somewhat in the 20th, but is still used to some extent. An alternative is "organic silk."
One way to test silks for weighting is to burn a small square. It is amazing to see what happens when a piece of heavily-weighted silk is burned. The sample retains its texture and shape, even though it has been burned. This means, of course, that the silk fibres have been burned out and what is left is the metal weighting. If the sample should be all silk, it will burn down to a little ball of ash.
Silk
Silk is a natural protein fiber, some forms of which can be woven into textiles. The best-known type of silk is obtained from the cocoons of the larvae of the mulberry silkworm Bombyx mori reared in captivity...
fabric is the addition of metallic salts during processing for the purpose of increasing the weight of the finished goods.
Unlike most fabric/yard goods which are sold by the yard (or metre), silk is sold to the wholesaler by weight. The first step in processing the silk fiber is "degumming the fibre," the gum being a byproduct of the production of the silk fibre by the worm. Approximately one-fifth of the weight of the silk fibre is lost in the degumming process, and manufacturers felt they had the "right" to replace this lost weight with a filler of some sort. Silk has an affinity for several metallic salts, the most common of which being iron, lead, and tin. It was discovered to be an easy process to return this weight lost in the degumming process by soaking the fibre in a bath of these metallic salts. This process was called weighting, and by increasing the weight of the raw silk, the merchant increased his profit. Weighting with some metallic salts did improve the drapeability of the fibre; however greedy merchants soon began adding more weight than the lost one-fifth; sometimes the final weight was increased tenfold.
While silk is a strong and durable fibre, the weighting process is highly damaging to the finished goods. If the garment is worn, it wears out quickly and is highly susceptible to perspiration, salt, and tears; if stored away it becomes brittle and breaks. The method of storage--cold/dark, etc., has no influence on these factors. One readily sees examples of this damage in antique American "Crazy Quilts" where the silk fibres have disintegrated while the cotton and wool fibres remain in good condition, even after 100 years.
This practice was widespread in the 19th century and decreased somewhat in the 20th, but is still used to some extent. An alternative is "organic silk."
One way to test silks for weighting is to burn a small square. It is amazing to see what happens when a piece of heavily-weighted silk is burned. The sample retains its texture and shape, even though it has been burned. This means, of course, that the silk fibres have been burned out and what is left is the metal weighting. If the sample should be all silk, it will burn down to a little ball of ash.