Factory primer in 67?

The primer surfacers used in the 70's we nothing special. The Big 3 paint manufacturers (PPG, BASF, Dupont) knew it was a good way to use up off-spec resins and misc. intermediates. In other words use up scrap materials.

The backbone resin system was a polyester base material. The cross linking (curing) mechanism was a thermo-set catalyst. The curing temperatures were around 425 degrees F and the dwell time in the ovens were normally 30 minutes at the desired temperature. There was usually a 20 minute ramp to temperature and a 30 minute cool down period. Bodies coming out of the ovens were normally too hot to touch for about a half hour.

Batch quantities were usually around 5000 gals on average. From what I remember you could get various shades a brick red or a medium grey colour. Again, colour dependent based on what "scrap materials " the manufacturers were trying to use up.

As far as durability goes with thermo-set polyester primers, sometimes you get a good primer and sometimes you get a great primer. It all depends what off-spec materials were used or not used during the batch formulation process. Today's primer surfacers have vastly improved in durability and corrosion resistance from the old polyester material.

Rust resistance was fair at best, mainly because of the pre-treatment products used. Chip resistance was actually very good for such a in-flexable product (surface hardness). Solvent resistance was good also, thus explaining why your stripper wouldn`t move the material.

Yes, you could leave the original primer on the vehicle but there may be hidden problems that you can`t see with the naked eye. If it were my car I`d remove the material mechanically, metal prep it, and put on a good 2K polyester high build primer. Use DP primer first if there is bodywork involved. This DP primer will seal the metal surface. Flash rust takes very little time to develop.

I hope this helps. Good luck with your project.


If you need further advise PM me and I`ll do my best to help you out.

All the best!

:glasses7: