I rethread for a few local jewelers in my area. I have a string of black diamonds to rethread and they are already on a cotton strand. I normally use Silkon but the #1 is too thick. Do you have a #0 or a different thread small enough to fit through? Thank you.
A good alternative may be Berkley® FireLine® 1- or 2-pound test thread. This thread is extremely thin and can be used with a very fine beading needle. It's very strong and holds up well to the sometimes sharp or rough edges of gemstone beads. FireLine is also UV protected, so holds up well to sun damage. This type of thread is slightly stiffer than the Silkon® you've been using, however it still creates a nice drape with strung beads.