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We’re getting a few days of good weather so I decided to paint my hood. Etch primer went on nicely, hi fill primer had some issues but it sanded out nicely. The single stage paint started flowing out really nicely, first coat nice and smooth, second coat went on nice, took care of the clouds from the first, 3rd and final coat was flowing out really nice, except I got some runs on the front of the hood, very frustrating.
So i watched a bunch of YouTube vids on fixing runs. I never liked scraping with a razor, a few times I did that on a guitar I had bad results. One video that was really interesting used bondo to prevent digging into the good paint with the edge of the sanding block. I decided to try it, if it failed, I’d be repainting anyway so nothing to lose.
Here’s the before …
I went too thick with the bondo, lesson learned. The object is to fill level with the high spots on the run, and feather the edges.
Next, wet sanded with 320 and 400. The bondo protected the finish, the runs came down with the bondo evenly.
Went to 600, then 1500 then 2000 grit.
A little buffing with Meguiar’s 105 and a 3” air buffer. Still some sanding scratches, but it’ll do for now.
Pro-tip...when using this technique on a run that large, start by using masking tape around the run and blocking the run with coarse grit paper. Once the run is knocked down to a manageable height, use metal glaze filler...easier to sand and much less work. Good job on your hood!
Pro-tip...when using this technique on a run that large, start by using masking tape around the run and blocking the run with coarse grit paper. Once the run is knocked down to a manageable height, use metal glaze filler...easier to sand and much less work. Good job on your hood!
I thought about using glaze filler, but I’m out and I didn’t want to run out to get some. I haven’t seen the masking tape method, but that makes sense. I have one more run to take care of, I’ll try tape and report back.
I saw at least 5-6 different methods on YouTube. Most common was scraping with a razor, but in my limited experience, I’ve found that one of two things (or both) happen, 1) the blade pulls the run off right down to the metal, or 2) the edge of the blade scratches the good paint.
I went through a range of emotions as i started through your pictures, from "what-the-holy-hell" to "WOW" what a clever idea! I have been painting cars for roughly 20 years, and even grew up from the age of 5 till my college years helping out in my uncle's collision shop, but I have to say, I have never seen this before. It makes total sense to save the paint.
I went through a range of emotions as i started through your pictures, from "what-the-holy-hell" to "WOW" what a clever idea! I have been painting cars for roughly 20 years, and even grew up from the age of 5 till my college years helping out in my uncle's collision shop, but I have to say, I have never seen this before. It makes total sense to save the paint.
all I can say now is FANTASTIC JOB!
I kinda went through that too. I mixed up the bondo and held the spreader over the area for a bit thinking “do I really want to do this?”
Pro-tip...when using this technique on a run that large, start by using masking tape around the run and blocking the run with coarse grit paper. Once the run is knocked down to a manageable height, use metal glaze filler...easier to sand and much less work. Good job on your hood!
I tried this on another run. I didn’t feel the masking tape helped at all, but the glaze worked nicely, a lot less work to sand.
Great job on the runs, looked scary at first but turned out nice. I'll look that up on Youtube as I have quite a few to fix. Of course that's on hold as I need a new left hip
Great job on the runs, looked scary at first but turned out nice. I'll look that up on Youtube as I have quite a few to fix. Of course that's on hold as I need a new left hip
Interesting video. Having been in and around the body shop and restoration business for over 40 years I'll admit this is a new one for me. I've fixed my fair share of runs with the razor blade method and it can work fine. Some runs take to it better than others. Just some constructive criticism from my observations in the video, there's a couple things I would do different. Using a hard block instead of the soft block he used would produce better results. You can see in the end as he's bragging about what a great job they did, it's still pretty wavy, and the harder block would have flattened the problem area out better, and gone quicker, too. Number 2, and this is the biggie for me, their lack of keeping the area clean while they were blocking. When wet sanding it's important to rinse your sanding sludge and debris away constantly, keeping a clean work area. They were sanding in their sludge right back into their work, making the job harder. I was cringing the whole way through that, looking for my sponge to rinse my work area.
Interesting video. Having been in and around the body shop and restoration business for over 40 years I'll admit this is a new one for me. I've fixed my fair share of runs with the razor blade method and it can work fine. Some runs take to it better than others. Just some constructive criticism from my observations in the video, there's a couple things I would do different. Using a hard block instead of the soft block he used would produce better results. You can see in the end as he's bragging about what a great job they did, it's still pretty wavy, and the harder block would have flattened the problem area out better, and gone quicker, too. Number 2, and this is the biggie for me, their lack of keeping the area clean while they were blocking. When wet sanding it's important to rinse your sanding sludge and debris away constantly, keeping a clean work area. They were sanding in their sludge right back into their work, making the job harder. I was cringing the whole way through that, looking for my sponge to rinse my work area.
Yeah, I noticed he didn’t keep the area clean. I use a rubber bondo applicator to squeegee the area off, then wash, pretty constantly. I hadn’t thought of the hard block, I used a soft block as well, I’ll remember this going forward. Thx for the input, there’s no way to teach experience!
I’m having a hard time getting rid of the sanding scratches. Look at the last pic and you can see some around the edge. I believe they’re from the 400, I’ve tried 800 and 600 but they remain. I’m afraid of getting more aggressive and cutting through. Suggestions?
Like they said in the video, the only way to get rid of sand scratches is with progressively finer sandpaper. You have to sand past the deeper scratches, meaning to get rid of them all, with the next step finer paper. 600 to get rid of 400, 800 or 1000 to get rid of the 600, then 1200, then 1500, etc. It's next to impossible to get rid of 400 scratches with 1000 or finer. Even 800 might be a stretch. Sure, you run the risk of cut through, but that's the downside of making a mistake. You have nothing to lose by trying to repair before repainting. You can then decide if it's bad enough to redo, or if you can live with the flaw.
It's also possible what you're seeing is a byproduct of what I was describing earlier. If you don't keep your work surface clean when wet sanding, you can get a little piece of grit under your paper that will make a bigger/deeper scratch than the sandpaper is making, and that is really hard to fix. It doesn't take much, either, and it happens really quick.
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