[GiorgioE82]

VIII. Lessons learned

There are MANY lessons that I learned throughout the process; if I were to tackle a similar project in the future I’m positive I’d see tremendous improvement over the end result of this one just based on these. I’m listing them below in no particular order. Also, I’m sure I’ll think of other things as days go by, so I’ll probably edit this one post to reflect that.
• Be obsessive about masking properly. Initially I masked around the roof rails and front and back glass while doing the resin and then I masked the whole car only prior to clear coat. If I were to do it again, I’d do a really good overall masking job for the whole car. The issue is that I ended up having some drips of resin on the paint (which were easy to take out with a razor blade once it dried) and what was worse, resin inside the glass surround. Most of it I was able to take out quickly but some of it became problematic as it dried WITH the rubber surround. So yeah, mask the crap out of it from the get go.
• The resin will (mostly) self-level. I used a plastic scraped to spread the resin thinly on the roof. This led me to lacking some control in the actual application, which then led to some of the resin spilling over the windshield trim and other places. Rather, pour some resin on the roof and use a wide brush to apply it to the roof. Any brush marks can be taken out during sanding.
• Mind the time. Pay attention to when the resin starts to gel. You do not want to apply past that point. One thing that I noticed was that, as you got closer to the moment it started to gel, the plastic cup holding the resin mix became increasingly hotter (as the reaction was taking place). Pay attention to that as an extra guide.
• Mind your PPE. This should go without saying. I used safety glasses, respirator and gloves for most of the process. However, during the initial scraping and removal of resin, I positioned my bare arms a lot on the roof. Big mistake. I was itching like crazy for the next two days. So, use long sleeves!
• Buy the clips. It’s not a matter of “IF” you’ll break some roof clips but rather “how many” will you break. As with many other BMW plastics, these things become brittle and almost impossible to remove without breaking.
• Use a machine polisher for sanding. I can’t overstate how much simpler the job was when sanding with the machine versus by hand. Make sure you buy enough of the appropriate grit sanding discs. I switched between a 3” and a 6” DA polisher to do most of the job.
• Heat your resin. After applying each resin layer, use a heat gun in low setting to carefully heat the roof surface. This will aid in removing any air bubbles in the resin application. Again, be careful and do not apply heat directly to any one spot. Keep the heat gun moving.
• Proper finishing. Although stated earlier, make sure you do a proper small test spot when starting the process of sanding and polishing the clearcoat at the end. Be consistent so that when you scale up to the whole roof, your process is able to be replicated and you don’t end up with the hazing issues I initially had.
• Replace the glass trim. It is infinitely easier to do this job with the glass rubber seals removed. Hence, budget new trim into the project. I’m sure glad I did!
• Keep a "wet edge". When doing the clearcoat. Make sure that, on your heavy coats, you do 50-75% overlapping passes of a wet application; wet almost to the point of creating drips but not really. You want the clear to come out smooth and wet. If you do end up with some drips, you can adjust a bit during the sanding stage.


(to be continued as I think of more)