After about 90 hours of pre-sanding, we have completed more than half of the work. Next comes applying primer, refined sanding and painting, all of which will be covered in this article.
Mentor
First I should talk about another important part of painting: my mentor. During the sanding process I always communicate with my mentor, our painter. He comes over from time to time to chat with me and see what I did and what I did wrong. I listen to almost everything he does, he is a true veteran, a very talented painter, he started learning painting at the age of 16, now he is 38 and has a deep understanding of painting. Usually he will not explain to us or customers how he does, because he disdains to do so. To him we are just a group of amateurs, he only needs a few tricks to satisfy us, that is probably 60% of his skills.
Yes, the truly excellent craftsmen never use all their strength to make a living, they just stay in their comfort zone. If you are not as professional as him, you will never find out that he could have done better. Yes, he never does his best, because the people who pay for his painting often do not have enough knowledge about painting. Our relationship as an apprentice was delicate. While I followed his every instruction, I also had to arrange work for him on other vehicles. He also inevitably did things on Nonna that I couldn’t do, such as PDR.
Although he is my mentor, he is definitely reserved with me. It was not because he was defensive against me, such as I would learn everything and fire him, but he thought it was “unnecessary”. The thought of a restoration shop owner who had no knowledge of painting and was eager to improve his painting skills made me dizzy, so I had to learn in person. But how much can I learn from him? This is definitely not something that can happen overnight. In his words, this is not a job for teenagers, because you must have enough patience. He once had two young apprentices working with us, and they had even learnt for 5 years already, but eventually left to do basic work in auto factories. They might just be too young, and there were too many uncertainties. They hadn’t even met the love of their lives, so there were too many unstable factors. I knew that if I wanted to get everything from him, I had to go through the path he had gone through.
Two and a half years ago, he taught me to paint Persian Kitty, so he knew what I had done. It was not out of flattery, he thought I had made great progress this time. He never flatters anyone, and in fact he is not a nice guy. Even I know that because I am younger, he despises me in his heart. How good? He said he has surpassed everyone in this city. This sounds flattering, but it is not. At least I know that I have spent more time than anyone else on this flat panel body. Of course, if you can do the best in a city of 15 million people in China, you can probably only barely pass in the world of restoration. So there is nothing to be proud of. I know there are many people in this city who can do better, they just don’t want to do it. In this industry, the real masters don’t all go to Rolls-Royce or Ferrari dealers, they sometimes hide in van dealers or small independent shops, and don’t like pressure or taking orders from anyone. Our painter is one of them. The more I learn, the more I know that he despises us in his heart. He said that my progress is mainly due to age. I am 2.5 years older than last time and have more patience. He thought the idea of teaching my sons to paint when they were 16 was crazy.
Primer filler
After the “rough” sanding of the body surface, the next step is to apply primer filler. In fact, the body treated with #800 is not only not rough, but also can form a mirror reflection at certain angles, which is enough to check the flatness. If you sand it more finely, such as #1200, the surface will be more silky, but it will reduce the adhesion of primer filler. I want the ultimate flatness, but stop at #800. Of course, you can also stop at #400 and leave the refined sanding to after the primer filler. But it has to be done anyway, sooner or later. The more you do it, the better the result.
There is also a small step before the primer is applied, which is to cover the exposed sheet metals with epoxy primer. This is to prevent rust, a very traditional solution. The epoxy primer does not need to be too thick, 10 µm is enough, which is basically the thickness of E-coat. We have a large area to cover, and because the drying time of 2K epoxy primer is very long, we used 1K. After being dried for a day after spraying, they actually only need 10 minutes of curing time. In order to reduce the number of material suppliers to avoid rejection reactions, the primer filler uses AUTOCOLOR P565-510, also from PPG, which will work in conjunction with PPG’s base and clearcoat. One of the functions of the primer filler is to fill low spots with primer rather than filler in the traditional sense. Although we have thoroughly sanded all low spots to make them transition with the surrounding paint, they are still low spots. There can be a difference of 60 µm between the bare metal and the original paint after sanding, which will be more visually obvious at the edges of the panels. It is best to fill them.
If you just spray the primer evenly on the body, the whole body will increase the same thickness, which does not make sense. The strategy is to spray those low spots first. The first coat may be 30 µm, so spray it again over first spray, so that the bare metal part can have a thickness of 60 µm. The third coat is to spray the whole car. If there is no primer filler, the new base coat may react chemically with the old paint, so the second function of the primer filler is to isolate the coat. It is summer and a slow release thinner P210-845 was used so it does not dry immediately after painting. Thicker paint films can crack if cured quickly. We did have one crack on the ridge on the side of the trunk. We left it to dry for 1 day after spraying and then left it in the sun for another 3 days to allow the thinner to evaporate.
Before the primer filler was sanded we had about 90 µm on the original paint panels and 150 µm on the repaint panels. Even with sanding and subsequent coats this is bound to be much thicker than factory thickness. Factory thickness was not the goal of the restoration at this time as the Nonna is still defined as a conservation example.
Refine Sanding
Next comes the re-sanding. Primer filler will roughen up the paint again, so #400, #800 or even #240. This is the last sanding before painting, and if there is anything that needs to be fixed before it is too late, what effect will be achieved will be determined here.
In the pre-sanding before the primer filler application, I was somewhat frustrated with completely solving the low spots, and tried to move this problem to the primer filler. So, since the surface was relatively flat before the primer filler application, would this refining sanding be easier? It depends on which landmines I left for myself. The rust spots on the hood and doors are like landmines. If they are not solved in the pre-sanding, they will be solved in the refined sanding sooner or later. There is no shortcut. I must admit that I only solved about half of the unevenness in the pre-sanding. This is not because I’m a slacker, but I couldn’t see it. The glossier surface of the primer filler showed more problems.
At the same time, primer filler will add defects to the surface again, and in large quantities, such as sagging. Sagging is not something we don’t want, they appear on low points that have been sprayed repeatedly. Since we are using primer to replace filler, there must be enough thickness for sanding down. So although refined sanding may seem to be just standing on the shoulders of giants, it is not simple at all. In particular, there is an additional difficulty: it is best not to penetrate the primer during sanding, so that the new paint will either react with the old paint in contact, or be sprayed directly on the bare metal and cause rust. Once penetrated, it must be re-covered, then re-sanded, and re-penetrated? So it is more endless work, be sure to be careful.
Refining sanding should usually start with #240, and the stronger cutting force makes the unevenness of the surface disappear faster. But I am a rookie in wet sanding, and I don’t have a feel for it yet. #240 is likely to penetrate the primer, especially in places with curves. Refined sanding emphasizes the strength of arms and hands. You can sand very hard in pre-sanding because bare metal is not terrible, but refined sanding must protect the primer. So I started with #400 to experience how to apply force properly, which includes using both hands to sand the panel at a vertical angle with the same force at both ends of the block, rather than using one hand to pre-sand hard like brushing a horse.
The process of sanding is also a process of discovering problems. Low spots will still be found in this process, even rust spots that were previously ignored. There will also be some bubbles during the primer curing process, and it is imperative to fill them again. This time, pin filler is used for filling, which is softer and more convenient than filler. Filling is done after #400 is completed. We painted many areas, and those low spots that were not filled with primer were filled again. Needless to say, then it was re-sanded with #400, so the efficiency of refining sanding was very low. In this process, I also used #800 flexible sponge sandpaper to handle the edges, so it is safe and will not penetrate the primer. This is especially important in concave and convex areas such as door handles.
It is worth mentioning that I focused on sanding down the pin filler area as required by my instructor. He said he would sand off 90% of it, so I understand that the pin filler is actually used as an indicator here rather than a filler. Yes, even the pin filler cannot completely fill the low point, so only the surrounding area can be cut. When the pin filler is completely sanded off, it means that the surrounding area has also been polished to the height of the pin fillet low point, so the low point disappears. In the end, you can’t expect all areas to have a thickness of 90 µm.
After the #400 is completed, it is #800, trying to eliminate the sanding marks left by #400. Then it is a thorough cleaning. I washed it in the hot sun for half an hour and unexpectedly found that the rear windshield had some water leaking again. After cleaning, you can see that even with only #800, the body has become shiny. This shine is enough to find the last remaining flaws, so it is to continue polishing, then cleaning, and checking. I invested more than 30 hours in total in fine sanding, not as much as the 90 hours of pre-sanding.
When the sanding was almost finished, I suddenly felt frustrated. I have spent so much time on this car, but I rarely spent time with my grandma during her last days. But what can we do together? She is destined to leave. And I am a little confused to commemorate her in this way. People’s memories are not eternal, and cars may be longer… I don’t know if this is the right way, but I am not ashamed of grandma.
Base and clear
Before the whole work started, I had decided that I would do the sanding, and our painter would do the base and clear coat. The main reason was that metallic silver is very difficult to master, and I didn’t want to ruin what I did at the last minute, even though this car is a reminder of my grandparents. So I won’t brag to people that I painted Nonna, I would say I sanded her if the audience understands what sanding means. There is no way to quantify the proportion of my work, sanding takes 99% of the time, and painting is actually only 2 hours. But this does not mean that painting is not important, because it can ruin the previous 99%. So, I just sanded her, and I will continue all the remaining work after the clear coat dries, installation and polishing. So it’s everything except painting, which is funny, I will say to people: “I did everything in this paint job except painting” and people will ask: “So what did you do?”
In terms of material preparation, the clear coat uses PPG DELTRON D894, which is a mid-range PPG product. On Bianca and Persian Kitty we used the top-of-the-line D8122, but it is not friendly to polishing and maintenance. The usage is 2 liters, which will cover the body twice. Equipped with DELTRON D812 slow thinner, because it is a hot summer now. Although the painting starts early in the morning, the temperature in the paint booth will soon reach 30°C. As for the base coat, it also comes from PPG suppliers and is mixed with PPG’s 9744 Brilliant Silver formula without additional adjustments. Silver is really tricky and it is difficult to completely replicate the original silver. Even Nonna’s donor, who was two months older than her, has different silver. So I don’t want to spend too much time on the mixing of silver. After all, there is almost no right answer. What I can do is to order twice we need. On the one hand, the larger the total weight, the smaller the mixing error. On the other hand, it is necessary to leave some spare paint for later repairs if we need it before the paint deteriorates.
The paint covered almost all exposed body panels, including those hidden under the bumpers and lower trim. The edges of the hood and trunk lid needed to be sprayed separately so that they would not stick to the masking film. All body accessories were set aside and sprayed separately. During the spraying process, even slow thinners did not work as the temperature increased, and the earliest panels began to cure after the first coat. We had chosen, no, God had arranged for us a fairly cool day, “only” 32°C, and higher the rest of the days.
Our painter was quite happy with his work. As he said, “experts” like him are more concerned with the details of the silver than the clearcoat, which is something amateurs like me would pay attention to. Well, in my opinion, if the silver cannot be seen with flaws from 1 meter away then it is perfect, but he would use a magnifying glass to find faults in the factory silver. After the clearcoat was applied we could finally examine the bodywork for any unevenness, the sides were almost absolutely flat! The hood, there are a few minor dents that may need PDR to improve. We had thoroughly cleaned the paint booth the day before, and the filter was only sprayed on one car, so the number of dust spots was well controlled.
After a few hours the clearcoat surface was cured and the paint booth doors were opened to allow the thinner to diffuse. After two days of natural drying in the paint booth, Nonna was taken out to the summer sun for baking, which is the biggest advantage of summer. The sun heats the panels to over 50°C and you can even see the orange peel change in a day. The shrinkage of the clearcoat is very intense. In this heat, the clearcoat is rock solid after just one day. As people complain, PPG’s clearcoats lose gloss after drying, whether it is D894 or D8122. We don’t really care about this problem because we will do a thorough wet sanding anyway. Now, Nonna will stay in the sun for another week before the chassis work is carried out, and the polishing will be carried out after 2-3 months. By then, the clearcoat will have completely shrunk and hopefully there will be no more sanding marks and phantom waves. I also admit that I have made a lot of progress in polishing, but maybe it’s still early! Let time test everything!