To protect the precious stones from the heat of the soldering or to control the soldering way.
Cover 6-7mm on the place where you want to protect, and proceed with the soldering.
Clean with water when you finish.
Attention: we canīt warranty 100% this, because depends of the stones type and the power of your torch.
When you protect Diamons or Emeralds donīt clean inmediately with water. Wait a short time.