Joints in an electrical cable are made by joining the ends of the conductors of two cables and applying and then curing a reaction mixture over the joint to form an elastomeric seal. The reaction mixture includes a polyene compound having an average of at least two groups containing aliphatic carbon-carbon double bonds capable of reaction with a thiol group, wherein at least one of such aliphatic carbon-carbon double bonds is separated from each of said aliphatic carbon-carbon double bonds by an aliphatic spacer group having a molecular weight of at least 1000 atomic mass units, an epoxy resin, a curing agent having at least two thiol groups, and a basic catalyst.