Last edited: 2/11/2019
Jewelers have been soldering on charcoal blocks as a refectory material for centuries. It may be for this reason that it's actually very difficult to find written information about it. Nearly every text I looked at had pictures of them being used but few mentioned that the blocks need to be wrapped with wire to prevent breakage and that they provide a reducing atmosphere. The best source of information I found was in Jewelry Concepts and Technology, a book by Oppi Untracht (at 840 pages it's considered by many to be the Jeweler's Bible). Untracht's book has a whole paragraph on charcoal blocks. Although it's not the only type of soldering block on my bench, charcoal blocks have several benefits.
Here are some of the benefits of charcoal blocks:
But they also have a few drawbacks:
Probably one of the most valuable things about the charcoal block is its versatility. Here are some ways to use and protect your block.
There are different ways to wrap your charcoal block so it will stay together. There is no rule about how to do it. I once had a boss that used duct tape, but it smelled horrible when he would burn it.
One unique quality of the blocks is that they can be used as a mold for pouring metal. Simply carve the block and then pour the metal in, it's a great way to make a simple casting or ingot.
Be sure to save all the coal dust. This can be placed on another non-charcoal block to provide the same reducing atmosphere benefits.
Broken pieces of the block can be saved and placed in a container for those objects that are odd-shaped and need to sit on a softer surface for support.
Be careful after soldering. The broken up pieces have embers that stay lit after soldering. I place a lid on the can after soldering to snuff them out and extend the life of the charcoal.
Rio Grande also currently carries a hard charcoal block. This is a wonderful block option and lasts much, much longer than its softer cousin. It still provides the same reducing atmosphere properties but you won't be able to carve it or push pins in it. I like to have both on the soldering bench; I can use the hard for most applications and then use the soft for those times when I need to push pins in or carve it for a small ingot. I hope this is helpful!