Unfortunatly, the only safe way to repair a knotted string of bead
is to restring and reknot the entire piece.
Especially if the necklace is old and worn, unless you wish to see
your customer more than once for the same repair…
Make sure you choose the proper threads for the job and be patient
if you’re not familiar with knots. (it usually drives me crazy) Once,
I had to rethreads a very long and very heavy amethyst sautoir. First
attempt was with three lenght of silk and one knot every three
beads… customer came back unhappy, for it broke after a week.
After a couple of other attemps I eventually used a thin beading
cable for strenght plus two silk threads for the knots.
Since then, I send these jobs to a local specialized subcontractor.
Saves me time and make happier customers.
Aix en Provence, France