These blocks are meant to be expendable, even the
compressed charcoal blocks. I would rather go through blocks faster
than have a smoldering block set my bench and shop on fire.
I have a bunch of charcoal blocks - some new compressed one and lots
of old ones, even small chunks of left over worn out ones that I can
stack adjacent to what I’m soldering to help hold it in position. I
did discover that if your charcoal block gets pits and cracks in the
top and becomes very rough and worn, simply take it outside and rub
it on a brick or old concrete block - acts like sanding paper but is
quicker. In short order you have a nice smooth surface to work on
againl And the charcoal blocks continue to live for another day.
And I have always spritzed mine with water at night when I’m finished
just to be sure. A friend who was a raku potter, burned his studio
down because he “thought” he had doused the sawdust he used for
firing the raku pots - he said it “looked” like it was thoroughly
"out" but it was smoldering deep inside and during the night erupted
in flames and burned his studio almost to the ground.
For that reason I keep an old cookie tin by my workbench and after I
have spritzed the carcoal blocks, they get put inside the cookie tin
and it gets closed up. Never had a problem this way.