One of the pop-out window frames was media blasted and all of the small parts that were epoxy primed earlier in the week were primed with high-build urethane primer. The purpose of the epoxy primer is to seal out moisture and form a protective shell around the metal, however it is not easily sand-able as it quickly clogs sandpaper. The purpose of the high-build urethane primer is to fill small surface imperfections to create a smooth surface, the urethane primer is readily sand-able and meant for this purpose. The right picture isn’t great but it shows how this works, the let side of the part has been sanded and the holes left by the rust pits are much shallower, the right side is unsanded and the holes left by the rust pits are still very deep. (compare to the un-blasted part at far left) Further sanding and additional coats of high-build primer (if needed) will yield a perfectly flat surface.

The media blasted small parts were hung and epoxy primed using a small detail spray gun. This went well with very little overspray. The garage temperature stayed warm enough that the epoxy cured without any issues.

Today brought the largest visual change the project has seen so far: full epoxy primer coverage of all interior and exterior panels. All of the metalwork has been leading up to this and when the last of the metalwork was completed there was no reason not to prime everything. Prior to priming the upper (white) parts of the bus the paint was stripped back to bare metal. This was necessary due to the rust, cracking, and general failure of the sun-beaten upper half. For the lower half a calculated risk was taken by scuffing instead of fully stripping. The epoxy primer is well suited to this type of application and the original West German Sikkens nitrocellulose lacquer is unlikely to lose adhesion when protected by the epoxy. The time savings are really a side effect since this decision was made primarily to avoid any distortion that could occur as the result of stripping the big flat panels of the lower exterior. The photos were taken very soon after application so the finish appears blotchier than it really is; since everything is the same color for the first time the shadows and lighting are beginning to play tricks on the eye.