As far as raw silk goes, you will want to boil it first until it divides itself into individual threads.
There are two silk proteins, one that actually makes what we call silk, and the other that makes the silk stick to itself. This second protein entirely coats the protein that you really want.
If you are using silk thread or silk fabric, or commercially produced silk fiber, it will already have been boiled to remove the sticky protein... if you are using raw cocoons, however, you will have to do it yourself. Sometimes, you will buy 'raw silk' and it will often contain little bits of leaves and such; this is actually raw, and still needs to be boiled.
Failing to do this can give you problems with it dissolving well, as well as minimize the effect of the silk in the soap.
The problem with this is grabbing the silk fiber out of the water after boiling it... so I don't. Instead, whenever I use raw silk (obtained a few cocoons from rare species of moth) I boil it in the water that I intend to use for lye. Once it is separated nicely, I let it cool, top off whatever boiled off, and then add the lye.
Never had a problem, and definitely helps the soap.