I get a number of odd and ends mags around here and at work - in EC&M I spotted CADWELD PLUS "Revolutionizes Exothermic Connections"
It is a Graphite 'mold' that a cup "Package" is placed. The wire or cable to be joined is below.
It doesn't say in the article - but it appears to weld or melt over at least bronze onto the copper. A rounded slug is over the but joint.
Maybe something for a job bid some day. Also - looks neat! e.g. welding lightening cable...
Martin