Friday, October 16, 2015

Return from Body Shop

After three weeks at the body shop the E36 is home once again. I am happy to say that the shop was able to remedy the problem without respraying and while it's not absolutely perfect it now looks a lot like it did when I took delivery last year. In other words, a lot better than it did.

Apparently the problem was the result of shrinkage in the clear that occurred when the clear fully cured after leaving the shop. The shop manager told me this can be caused by a number of factors but it is more likely to occur on horizontal surfaces (like my hood, where it was most obvious) because the clear is often applied in a greater thickness there. As the story goes, the thicker the clear the slower the evaporation of solvents in the lower portion of the clear. When, after several months, the solvents do finally make their way out and the clear fully hardens it can shrink, leaving a pattern of tiny cracks that diffuse the light and cause the hazy / out-of-focus look I showed last time.

This doesn't typically happen on factory paint because they bake the finish at very high temperatures prior to assembly. This increases the evaporation rate of the solvents and helps the chemical curing process. Baking the finish with the same temperature is not practical in the field because this would likely cause damage to the plastics, wiring, electronics and other components mounted to the body. So shops must therefore strike a balance and apply the highest temperature required for a good cure while preventing damage to the vehicle. Unfortunately shops don't always get that balance right the first time and my car is proof.

They fixed the problem by buffing with a combination of compound and polish. No sanding was required. There was some concern initially that the shop had received a bad batch of hardener but the shop manager pointed out, had that been the case, the cracks would not have been just a surface phenomenon and they wouldn't have been able to correct the problem through buffing alone. Incidentally, it didn't actually take them three weeks to correct the paint but they wanted to keep the car just in case the problem redeveloped. Had they needed to refinish the car I would probably be a bit more skeptical about the finish at this point but I think it's fair to say it's now fully cured and unlikely to shrink again.

The thing to take away is that every car painted in the field leaves the shop (on purpose) with clear that is not fully cured. This is why they tell you not to wrap a newly-painted car for at least 30 days. Based on this experience I'd probably consider 60 days as a minimum.

Of course, the E36 won't be home for long. I've scheduled it to return to the dealer so my technician can do all the work I planned to do prior to the paint headache. My hope is to complete this work before the cold weather sets in. Once that's done I'll have only one step remaining in the rolling restoration I started over five years ago: new leather.

Mileage: 261300