Charcoal soldering block gives you 3 to 5 times the life. Charcoal blocks retain heat and absorb oxygen. Preferred by jewelers to avoid firescale during soldering. Soft charcoal blocks are to position pieces for soldering by pushing pins into the block holding your work in place. Rated up to 3000F.
Use when soldering small parts. Charcoal adsorbs oxygen and helps avoid firescale.