There are a few distinct characteristics of thrown silk waste you will notice right away when you purchase this fibre. First of all, the fibres may be dyed in multiple colours and they will also be stiff with sericin (gum) which is residual from the silkworm's spinning process. I do not recommend spinning before degumming the silk as it is unpleasant and produces a hairier yarn than if you degum first. The colours are fugitive - they will wash out when you degum to leave the silk soft and shiny.
A.1 pound raw silk (with sericin 'gum')
B.4 oz washing soda (sodium carbonate)
C.4 oz soap (grated Ivory soap bar)
1. put washing soda and soap into pot with a few inches of water
2. keep at low simmer until soap and soda dissolve
3. add enough lukewarm water to float silk comfortably
4. add silk and simmer until soft ( 1 hour) remove a sample and rinse to determine if it is soft enough
5. rinse while hot, to remove most of the sericin, soap and soda
6. add about 1/3 cup vinegar to neutralize alkalinity and soak for 10 min
7. rinse in clear water
Once you degum the silk by simmering it in a soap and soda solution, the silk is ready to dye (or not) and spin. I place the wet silk either in aluminum pie pans or on a piece of plastic wrap for the dyeing process.