Repairing scrape - fingernail does not catch

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PostPosted: Sun Mar 19, 2023 10:51 pm
Hi, all,

Yesterday I discovered someone hit my 'Black Sand Pearl' Corolla and damaged the rear bumper. I was able to remove all of the damage but for a vertical scrape. I have tried unsuccessfully to remove the scrape using an LC Orange Pad with GG Fast Correcting Cream, Lacquer Thinner, and Magic Eraser.

I tried using mineral spirits to see the effect, and it might have darkened the scrape on a miniscule level, though I suspect it was wishful thinking (and light could have played a factor). Based on these findings and the fact nothing I have done has improved the scrape, I suspect the paint must have been stripped necessitating touch-up paint.

But, my confusion arises from the fact the scrape is smooth to the touch and practically level with the surrounding paint. That is to say, I am unconvinced a blind person could feel a difference and identify the scrape’s location.

Any ideas on what has happened and how to fix it?

Here are a few photos:

Before A.jpg
Scrape without mineral spirits 1

Before B.jpg
Scrape without mineral spirits 2

Scrape with surrounding area wet-sanded.jpg
Scrape with surrounding area wet-sanded (pre-polish)

After C.jpg
Scrape with mineral spirits applied



Thanks muchly!

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PostPosted: Mon Mar 20, 2023 10:02 am
Looks like the clear coat is gone in that area.
Buffing won't correct the problem.
1968 Coronet R/T


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PostPosted: Mon Mar 20, 2023 11:09 am
'68 Coronet R/T wrote:Looks like the clear coat is gone in that area.
Buffing won't correct the problem.

Thanks for your response. Do you think some of the colour is still there. That is to say will applying clear coat and wetsanding resolve the issue?

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PostPosted: Mon Mar 20, 2023 11:47 am
It appears to be, so you can give that a try.
The thing to be concerned about is whether the base coat will wrinkle when clear is applied.
You will need to put a very light coat on first and give it time to flash. The apply additional coats until it's even with surrounding surface.

Hopefully one of the pros on here will give you a more detailed answer.
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PostPosted: Mon Mar 20, 2023 11:52 am
GOOD INFO ABOVE. put some wax & grease remover on it OR water THIS is what it will look like after clear. one thing i would NOT get lacquer thinner on it... it WILL attack the broken edge of the clear, quite quickly. i really doubt any clear is going to help you, other than making a dull spot glossy. i can't tell in the picture but the color doesn't look anywhere close to what it should be. sad to say if you want it fixed you had better head to a GOOD body shop. they can spot that area and clear the complete panel. with the color and texture this is a rather involved job and require a talented painter to make it perfect.
Jay D.
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PostPosted: Mon Mar 20, 2023 6:06 pm
s-c-3-1-3 wrote:But, my confusion arises from the fact the scrape is smooth to the touch and practically level with the surrounding paint. That is to say, I am unconvinced a blind person could feel a difference and identify the scrape’s location.


On an edge like that I'd agree, most people couldn't feel a difference of maybe 50μm, especially if the edges were slightly feathered. People who are blind often have remarkably well developed other senses, including touch, so I wouldn't count them out, nor would I count out an experienced painter or panel beater, many of whom can feel things you can't see.

Although some can't help themselves, most of us look at paint rather than feel it. Even looking at pictures of it, I can see that you're down to the plastic and no amount of buffing will restore paint that isn't there.

We have no 'before' photos, so I can't say to what degree you've made the initial damage worse, but I can say that I've never seen a scrape where the paint edges are not raised, even on one side.

One of the tricks of detail paint repair and correction is not to make the surface worse than it was. Sanding the surrounding area has absolutely no benefit and means you're extending the repair way beyond the damage, something that only has relevance if you intend to respray.

As for concerns about thinners attacking the base coat edges, this is not the problem. Rather, the thinners will attack the primer and get under it, causing softening and wrinkling of the edge. Light coats of thinned acrylic (or lacquer) can help reduce this problem, especially when done on a warm to hot panel (hastening thinners flash off and reducing the time for the thinners to attack the primer to substrate join). Using unthinned acrylic paint can also work, especially if any resultant wrinkling is then bladed off level before subsequent coats, this technique being more relevant in cases where the original paint is a bit thicker and some filling is needed.

Can that damage still be repaired by touch up? Yes, depending on skill level of the person doing it.
Chris



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PostPosted: Mon Mar 20, 2023 6:46 pm
NFT5 wrote:
s-c-3-1-3 wrote:But, my confusion arises from the fact the scrape is smooth to the touch and practically level with the surrounding paint. That is to say, I am unconvinced a blind person could feel a difference and identify the scrape’s location.


On an edge like that I'd agree, most people couldn't feel a difference of maybe 50μm, especially if the edges were slightly feathered. People who are blind often have remarkably well developed other senses, including touch, so I wouldn't count them out, nor would I count out an experienced painter or panel beater, many of whom can feel things you can't see.

Although some can't help themselves, most of us look at paint rather than feel it. Even looking at pictures of it, I can see that you're down to the plastic and no amount of buffing will restore paint that isn't there.

We have no 'before' photos, so I can't say to what degree you've made the initial damage worse, but I can say that I've never seen a scrape where the paint edges are not raised, even on one side.

One of the tricks of detail paint repair and correction is not to make the surface worse than it was. Sanding the surrounding area has absolutely no benefit and means you're extending the repair way beyond the damage, something that only has relevance if you intend to respray.

As for concerns about thinners attacking the base coat edges, this is not the problem. Rather, the thinners will attack the primer and get under it, causing softening and wrinkling of the edge. Light coats of thinned acrylic (or lacquer) can help reduce this problem, especially when done on a warm to hot panel (hastening thinners flash off and reducing the time for the thinners to attack the primer to substrate join). Using unthinned acrylic paint can also work, especially if any resultant wrinkling is then bladed off level before subsequent coats, this technique being more relevant in cases where the original paint is a bit thicker and some filling is needed.

Can that damage still be repaired by touch up? Yes, depending on skill level of the person doing it.

Thanks for your response. I had never considered that about blind people, and I hope my comment did not come across as rude or insensitive.
Here is a photo before any work was done on the vehicle:
Before626.jpg

I started with my least aggressive combination (LC Orange with GG Correcting Cream working my way up to a LC Yellow with GG Fast Correcting Cream). Only when none of my combinations made any improvement on the scratches did I resort to wetsanding the scratches.
How would you go about fixing this damage? While I understand bringing it to a body shop might be the best option, I would rather try to tackle it myself.
For what it is worth, this bumper had been replaced previously due to a different incident.

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PostPosted: Mon Mar 20, 2023 7:56 pm
If it was me, I'd brush touch that as a cheaper alternative to respraying if keeping cost down is your objective, rather than achieving perfection in the repair.

You'll need to get some acrylic touch up paint made up in the correct colour and some acrylic (aka lacquer) thinners in the best quality you can get. Just a 10-15ml bottle of the paint will be more than you need - maybe available pre-mixed from an auto parts store.

Clean the surface with Prepsol or wax & grease remover. Thin the paint about 1:1 with the thinners in a tiny cup. 5-6 drops of each in a thimble would do. Apply the paint in multiple thin coats, allowing each to dry 5-10 minutes between coats. Panel should be room temperature - not hot and not cold.

When applying the paint use the brush at a very low angle to the panel and initially just touch the paint to the surface then raise the brush so that it's not actually touching but the surface tension of the paint is drawing the paint off the brush as you move along. This is important - you want the top of this repair to be as smooth as possible and putting brush strokes in it isn't the way to go. Keep your paint application INSIDE the damaged area.

You may need 4 or 5 coats but the idea is to build it up a bit higher than the surrounding surface so that when it shrinks back it will be level or a bit above. Allow 24 hours to dry and, if necessary add more paint to bring the level up.

Once dry and shrunk back, take a soft cloth and wrap an end around your finger. Put some polish or gentle cutting compound on the tip and start rubbing, Use almost no pressure and fast movements side to side along the repair, using your finger to feel the ridge and keep your polishing ONLY to that raised welt. A trade trick is to place some electrical tape on the surrounding surface to protect it from rub throughs. Stretch it out well to reduce the thickness and place as close as you can to the edge of the repair. It may take a while but keep the cloth wet and the surface will smooth out and begin to level. Don't try to take it perfectly level with the surrounding paint - this will just expose the edges. Leave it slightly raised, like a scar. If you rub too much and go through you'll have to start again.
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PostPosted: Mon Mar 20, 2023 11:37 pm
NFT5 wrote:If it was me, I'd brush touch that as a cheaper alternative to respraying if keeping cost down is your objective, rather than achieving perfection in the repair.

You'll need to get some acrylic touch up paint made up in the correct colour and some acrylic (aka lacquer) thinners in the best quality you can get. Just a 10-15ml bottle of the paint will be more than you need - maybe available pre-mixed from an auto parts store.

Clean the surface with Prepsol or wax & grease remover. Thin the paint about 1:1 with the thinners in a tiny cup. 5-6 drops of each in a thimble would do. Apply the paint in multiple thin coats, allowing each to dry 5-10 minutes between coats. Panel should be room temperature - not hot and not cold.

When applying the paint use the brush at a very low angle to the panel and initially just touch the paint to the surface then raise the brush so that it's not actually touching but the surface tension of the paint is drawing the paint off the brush as you move along. This is important - you want the top of this repair to be as smooth as possible and putting brush strokes in it isn't the way to go. Keep your paint application INSIDE the damaged area.

You may need 4 or 5 coats but the idea is to build it up a bit higher than the surrounding surface so that when it shrinks back it will be level or a bit above. Allow 24 hours to dry and, if necessary add more paint to bring the level up.

Once dry and shrunk back, take a soft cloth and wrap an end around your finger. Put some polish or gentle cutting compound on the tip and start rubbing, Use almost no pressure and fast movements side to side along the repair, using your finger to feel the ridge and keep your polishing ONLY to that raised welt. A trade trick is to place some electrical tape on the surrounding surface to protect it from rub throughs. Stretch it out well to reduce the thickness and place as close as you can to the edge of the repair. It may take a while but keep the cloth wet and the surface will smooth out and begin to level. Don't try to take it perfectly level with the surrounding paint - this will just expose the edges. Leave it slightly raised, like a scar. If you rub too much and go through you'll have to start again.


Chris,

Thanks for your detailed response. I hope you don't mind, but I have several follow-up questions (apologies for the quantity and potential stupidity):

1. I have debated purchasing an airbrush. Given this colour is metallic, would using an airbrush yield better results? I am hoping to achieve as much perfection as possible. If an airbrush would yield better results, would the process be the same, etc?
2. I noticed your method makes no mention of adding clear-coat. Without clear-coat, would the finish not be dull and more noticeable?
3. Because the plastic is exposed, do I need to add primer?
4. The local retailer that sells automotive paint is Rondex, and they sell acrylic enamel. When I asked whether clear-coat could be added to it, she said clear-coat does not work with acrylic enamel and that it is already mixed in. Would acrylic enamel work fine?
5. Given your last sentence, can this work be reversed? Put otherwise, if I am dissapointed with how the touch-up turns out, can I easily enough remove it and restart?
6. When you say to keep the towel wet, do you mean wet with the compound?
7. Would any brush work? I believe the one included in the local automotive store selling acrylic enamel is akin to one found in nail polish.

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PostPosted: Tue Mar 21, 2023 12:31 am
s-c-3-1-3 wrote:would using an airbrush yield better results?

Possibly, but unlikely given that you'd be refinishing a much bigger area, making the repair more likely to be noticed, especially being black.

s-c-3-1-3 wrote:Without clear-coat, would the finish not be dull and more noticeable?

Acrylic dries glossy if you use a high quality, slow drying thinner, which I recommended. Polishing it helps bring up the gloss as well.

s-c-3-1-3 wrote:do I need to add primer?

No, the paint will adhere to a small area like this quite well, provided it is cleaned as I detailed.

s-c-3-1-3 wrote:Would acrylic enamel work fine?

Yes.

s-c-3-1-3 wrote:can I easily enough remove it and restart?

Simply wipe off with a cloth soaked in acrylic/lacquer thinners.

s-c-3-1-3 wrote:Would any brush work?

Yes, but the nail polish brush type included with the paint is probably going to work better. Note in my instructions that you don't actually "brush" it on so the type of brush isn't so important as its ability to hold the paint without drying too quickly. So a bigger brush or the dagger type often recommended doesn't work as well.
Chris
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