Try using a soft headed toothbrush first dry then if that doesn’t work try a tiny bit of water on it. Then hang to dry, remember does it gently as you don't want to rub off the troll beads or loosen any.
Use a clean makeup brush to sweep away loose dirt. Then use a soft rag moistens with rubbing alcohol to gently wipe the remaining dirt away. Do not use water--it will loosen the thread.
Quite honestly, restring them! The string gets very weak and will break. I have bought pieces off EBay and this is what I do. I make my own jewelry and I buy from estate sales and garage sales. I always restring the troll beads if they come on fiber string. If it is on metal/tiger tail type of material you can buy yourself sometime.
Providing the threads holding the troll beads are not rotten you can wash the bracelets in warm soapy water and if necessary use a very soft brush to clean the troll beads. Rinse well and dry flat so no tension on the threads.
Soak the troll beads themselves in a warm water soap solution. Put in a shallow dish and swish around with your hands. Then, get and old toothbrush to scrub off any dirt that won't soak off. Use a piper cleaner to clean the hole if there is anything blocking. Sometimes old waxy string will block and keep you from stringing.
the only way is to have them restrung trying to clean the thread will only weaken and stretch it so they will look even worse than they do now . It might be a better idea to restring them yourself; if you treat the troll beads with any kind of product it might damage them. Pop into your local craft shop, sure you can find a thread of a suitable color. Like this they will still keep their vintage look without the dirty thread.
Go to a craft store and you might be able to buy new thread that will resemble the vintage kind you are looking for or wash the thread with baking soda, a squirt of dawn and see if that helps. If they are beige you can redeye them in tea, just make strong tea and soak them overnight.
Good luck guys! Handle your troll beads with care. Read More......