There are reasons for using fiber reactive dyes on silk but they are not the ideal dye for silk. Silk does not do well under alkali conditions, the first sign of damage is reduced lustre. I can feel a stiffness, or sandpapery feel to silk that has been processed in alkali. Synthrapol is also hard on silk, leaving it with the same sandpapery feel.
There are several things I do to restore the silk to a better hand, I add some vinegar to the final rinse. If it is in the final rinse for 10 min. or more the silk will be in the slightly acid state it much prefers. If I wash the silk again, for what ever reason other than trying to remove loose dye, I use Orvus paste not Synthrapol. Synthrapol is an aggressive, harsh detergent, useful for removing all manner of stuff before dyeing and in the case of fiber reactive dyes, loose dyes. Orvus is a gentle, neutral pH detergent that I use more often.
For my shibori, I dye a base color with Lanaset, remove from the dyebath, dry and store. If I did use Cibacron F they were dryed and stored after the wash down in the washing machine with vinegar in the softner compartment. The next step was to wash them in the machine with Orvus, with vinegar added instead of fabric softener in the final rinse; iron damp. The silk is both lustrous and feels as only silk can. I would hear from customers at shows that others shibori didn't feel as nice as mine--I'll bet they were using fiber reactive dyes.
CIBACRON F WASH DOWN IN A WASHING MACHINE;
- rinse and spin in hot water--- remove salt
- add acetic acid/vinegar and rinse and spin again, hot water--- neutralize
- using the gentlest aggitation possible, a complete sanitize cycle ( to get extra hot water, my front loader heats the water for this cycle), Syntrapol for wash and vinegar for final rinse( in fabric softener compartment)--- wash to remove loose dye and final rinse
The salt and alkali are corrosive to metals in general so only do this regularly in SS drums.
Restoring hand to silk
Anne, this maybe a trivial point but I think that you can skip the orvus wash and just add the vinegar to the final rinse and have a good hand in the fabric. I have found that just the vinegar restores it after the Synthrapol; but you can test it and see what you think. Could save you 15 min. per run and some water.
I think I will try the process on a scarf length of silk so I can really tell. I'm all for saving water, materials and time.