Saturday, December 12, 2009

Suzhou Silk Factory 2: The Cocoon Cooker

I suppose many people have the job of watcher. In silk factories there are many watchers; and one of these is the watcher of cocoons. The cocoons flow down on a conveyor belt from where they are kept, and the watcher has to watch for those too large (likely to be double cocoons), and those that are spoilt (the moth emerging, or the cocoon too thin or dirty). The rest are deemed to be the perfect ones and used to reel into silk.

But before the cocoons are processed further they have to be stifled. In this factory they were cooked. There is a watcher for this too. Great tin baths full of intact single cocoons

are tipped into trays at the top

and these trays are sprayed then dipped with boiling water on a slowly moving conveyor so that the glue, 'fibroin', holding the silk strands together is dissolved and the cocoons start to soften and unravel.

It is the most energy-hungry part of the process and some silk mills in Hanzhou run this process using the sun.

That is the official reason for the cocoon-cooking process, but there is also another one. As the cocoons are cooked the pupa inside the cocoon is killed. The metamorphosis stops and there is no danger of the silkmoth inconveniently emerging and destroying the continuity of the thread. A broken thread has to be spun. It is not as lustrous as reeled silk and not as valuable, and I suppose makes silk unwearable by vegetarians.