Cuocere / Degumming

To make the thread soft and white, the sericin needs to be removed by boiling the thread in a solution of soap and water. Alternatively, the thread can be used "raw" and the finished fabric de-gummed.

Exact details vary somewhat, but all involve near-boiling water and soap. I found the most information on sites for industrial silk processing such as FAO's Silk Reeling and Testing Manual.

Degumming Ingredients

Soap - Neutral soap made from pure olive oil or olive oil foots and soda.

Classic Ivory Bar Soap - Ph 10.4
Neutrogena Original Formula Facial Bar - Ph 8.7 - 9.2

Bon Savon has castile soaps with a neutral Ph, made from olive oil.

I've used "Kiss my Face" brand olive oil soap, and had good results. It's not neutral Ph, but it tests milder than Ivory (which I've also used with good results.)

Soda - Sodium carbonate (Na₂CO₃)

Sodium carbonate is also called soda ash and washing soda. The carbonate ions from dissolved sodium carbonate precipitate magnesium and calcium ions from hard water. These metal ions would otherwise combine with soap or detergent and form an insoluble scum that would stain the laundered clothes.

Na₂CO₃ = washing soda = sodium carbonate
NaHCO₃ = baking soda = sodium hydrogen carbonate.

I called Arm and Hammer, and they said that their Super Washing Soda only contained sodium carbonate - no bleaches, perfumes or other ingredients, so that's what I use.

Water - Demineralized water. You don't want hard water minerals combining with the soap and forming scum.

I've used Brita filtered water and distilled water. I'm not sure how demineralized they are, but they're better than my (hard) tap water.

Degumming Formula and Directions

Silk: Weight of Silk (WoS) in grams = __________g silk
Soap: WoS x 0.25 = __________g soap
Soda: WoS x 0.009 = __________g soda
Water: WoS x 70 = __________ml water

Measure out the ingredients based on the weight of silk.
Combine in an appropriately sized pot for the quantity of water.
You don't want it too shallow.
Heat until the soap is dissolved. Add the skeined silk.
Simmer at 95 C for 30 minutes.
Remove and rinse in fresh hot water.
Repeat the degumming, but without the washing soda.
Alternatively, repeat with water alone.
Rinse well. Rinse and soak in clear water with a "glug" of vinegar.
Rinse again.
At this point I put it on a swift to re-skein it neatly.

It's okay if you need to use extra water. This formula was intended for industrial use, where everything used adds to the cost.

Expect to lose 20 - 25% of the weight of the silk in gum.