In Praise of Life-Calk

It's nice to come across modern hi-tech materials used in other applications which solve car restoration problems without detracting from the originality of the car. Life-Calk is high on my list of favourite wonder compounds.

Life-Calk has actually been around for many years. It is, quote - 'a one part Thiokol based polysulfide rubber sealant and bedding compound . . . . cures to an unbreakable watertight rubber seal'. It is manufactured by BoatLife Inc. and is available from boat chandlers. In my experience it acts like a strongly self adhesive rubber gasket which bonds to practically anything. I have only used it for cold applications, rather than in assemblies which get hot.

A simple application is fixing a rear view mirror, fitted with a rubber suction cup, to the windscreen. When black Life-Calk is used it is indistinguishable from the original black rubber. However, it does keep the mirror in place for years, unlike the suction cup on its own which, when no longer new, falls off after every bump in the road.

One of the difficult parts to assemble is the glass in Rotax headlamps and 3" side lamps. The rims were originally glazed by spinning the rim, glass and rubber gasket - an aluminium channel section was 'metal spun' round a flange inside the rim and round the glass and gasket. When the glass gets broken or is removed to repair and rechrome the rim, it is very difficult to reassemble while maintaining a water seal. The remnant of the aluminium channel is not normally reuseable. Black Life-Calk can be used on its own to form a new combined adhesive seal and gasket to keep the glass in place. The rim is cleaned and laid flat, a generous thickness of seal is carefully applied all round the face of the inner flange, and the cleaned glass is placed in position with minimum compression to maintain about 1mm thickness of the 'gasket' seal. Left for 24 hours the seal cures and can then be trimmed with a sharp blade to remove excess (At this stage the rubber-like quality of the material can be appreciated). Job done! Spring clips can be added if the headlamp rim section allows for their fitting, but in my experience this is not necessary.

Postscript -

Recently I have found a similar product marketed by 3M Company which seems to match the performance of Life-Calkl. This is their Marine Adhesive Sealant 5200 which is a 'polyurethane prepolymer' formulation.