Water Sealing Techniques

3M ScotchCast info:

3M Product Page for ScotchCast Electrical Resin

What is ScotchCast?

3M™ Scotchcast Electrical Insulating Resin 4 is a two-part, epoxy insulating and encapsulating resin. This resin, mixed in its unique two-part bag, generates its own heat to cure. Its compatibility with solid and synthetic cable insulations and jackets makes Resin 4 an excellent insulator and sealer for cable splicing.

  • Excellent multi-purpose moisture sealing resin
  • Two-part closed mixing pouch simplifies mixing and pouring
  • Bonds to itself and to most modern cable jackets
  • Thermal setting; designed to not melt or run once cured
  • Designed to be stable at elevated temperatures
  • Generates its own heat to cure
  • Tough & Oil resistant

--From 3M Product Data Sheet (pdf)

ScotchCast Directions

  • Mix 1.1 parts of Part A(Clear) with 1.0 parts of Part B(Black) for 1-2 minutes, or until compound heats up.
  • Apply Mixture to part
  • Let Set for 4-6 hours
  • Celebrate if it's waterproof!

Note: ScotchCast works best for waterproofing cable splices, it will dry into a hard plastic, so it is not well suited for application on movable pieces (ex: It doesn't work well for waterproofing cables into a pelican box).


We use o-rings to seal each of the watertight enclosures. The end caps all have a groove carved in them along the outer side, into which we place a rubber o-ring. When the end cap is placed into the housing, the o-ring is compressed, forming a seal.