no quinto artigo sobre o assunto das sedas, tive a honra de receber um comentário do próprio Mr. Peter Zwicky com quem troquei umas mensagens muito esclarecedoras, a que teve a amabilidade e paciência de responder e que hoje partilho com todos vós, com a sua permissão – por isso em todos os artigos sobre este assunto o título foi corrigido e acrescentado um aviso:
in the fifth article on the subject of silks, I had the honor to receive a comment from Mr. Peter Zwicky himself, with whom I exchanged some very enlightening messages, which he had the kindness and patience to answer and which I share with all of you today, with his permission – so in all articles on this subject the title has been corrected and added a warning:

Aviso: por favor, sempre que me refiro a seda vegetal leiam fibra vegetal 
Warning: Please whenever I refer to vegetal silk read vegetal fiber

Arte Fiber – Tell Zwicky

Zwicky natural silk

These were the Zwicky threads I talked about – I’ll transcribe Peter Zwicky words

“As far as silk is concerned, I need to clarify a few details. The word “silk” is basically related to a fiber produced by an animal, for instance a worm or a spider. The designation “vegetable silk” is not correct and should not be used, as the fiber comes from a plant. “Vegetable fiber” would be the correct wording, as Polyester is a “synthetic fiber”.
“Silk is probably the most noble fiber. It’s strong, shiny, elastic, durable, dyeable in all possible colors, and can be disposed with no damage to the environment. Unfortunately, it’s very expensive, because it’s rare, needs lots of human work and cannot be produced everywhere. There are several worms (future butterflies) capable of producing silk, the best and most noble being the Bombyx Mori, mainly cultivated in China an Brazil. Other types of worms are found in Thailand, India, etc., producing lower qualities of silk. The Bombyx Mori only eats mulberry leaves and is therefore bound to regions where mulberry trees can grow. During the processing of silk, the product is divided into two categories, the real or natural silk and the schappe silk. The real silk is the fiber that is unwound directly from the cocoon. It’s a continuous filament, as it’s very long. Normally, you can unwind around 800-1’000 meters from a cocoon. As the fiber gets thinner towards the inside of the cocoon, the fiber starts to break, you cannot continue to unwind it. The remaining part of the cocoon is then torn apart and the resulting short fibers spun like cotton. The same procedure is applied to cocoons where the butterfly managed to escape from the cocoon. That’s what we call the schappe silk (from the French word “échapper”, meaning “escape”, which is related to the escape of the butterfly destroying the continuous filament and obliging the producer to extract a short fiber). The silk in its chemical composition is the same in both products, but one is made of very long single fibers (real silk), the other one of short fibers of 3-4 cm (schappe silk). It’s clear that the real silk is by far the most noble one. It’s also the only one that has this very particular shine once dyed. The dyeing process removes the protection coat that the worm adds to the fiber during the spinning of the cocoon (it’s a glue, representing 25% of the total weight) and allows the silk to reflect the light on its clear surface. The real silk is what you will find in scarves, ties and clothing fabrics, where the schappe silk is used for underwear, socks, etc.”
“An embroidery looks the best if real silk is used. That’s what you have with the skeins of Zwicky Silk you managed to obtain. In Switzerland Zwicky produced two types of silk threads. One made out of real silk and one made out of schappe silk.
The real silk Zwicky products were called Filofloss (thick thread for hand embroidery, on small hanks) and it was the Rolls Royce of embroidery threads. It’s 100% of the best Bombyx Mori from either China or Brazil, spun, twisted and dyed on high quality machines; Universel (for machine sewing, on bobins), AMF (for industrial machine top stitching, on hanks) and Flora (for button holes in private homes, on very small bobbins).
The schappe threads were called Chalet (for machine sewing, on bobbins) and Iris (for home sewing, on very small bobbins). Unfortunately, with the closing of the production in Switzerland in 2000, the embroidery silk of Zwicky was discontinued.

If you have Zwicky samples of an embroidery thread, it’s Filofloss (4 meters on each hank). They are made of the best real silk. You can easily distinguish real silk from schappe silk, as real silk shines much more because of its continuous filaments and has no hairy structure.”

Thank you so much Mr. Peter Zwicky for such a great information – I think I have a  Rolls Royce at home!

[Schappe Silk -Spun (not reeled) silk yarns that have been degummed by a lengthy and very smelly fermentation process.      https://texeresilk.com/article/silk_information_dictionary]