Problem After Sanding Down Touch-up Paint

S

slvrshadow94tt

New member
Hopefully someone can give me some good advice.



I repaired a chip in the paint on my driver side front fender over the weekend. I followed "David's" chip/scratch repair instructions that I printed off the Autopia "Learning" section.



I wet sanded the touch-up paint down to the level of the original, first using Meg's Unigrit 1000 and then Meg's Unigrit 2000, pulling the block toward me only. Then I followed up with 3M's Perfect It II to take off the scratches left by the Unigrit blocks. It looked awesome until I changed my viewing angle in the light.



PROBLEM:(

Now it appears that the level of the clearcote around the touch-up is lower than the level of the paint repair, creating a "DING" effect when light reflects off the surface! Looks like I fixed one problem and created another:wall !!!!



What can I do to fix this? Should I purchase clearcote touch-up paint at the dealer and build up around the chip? And will clearcote touch-up applied over factory clearcote create any unwanted effects? How can I avoid this problem on future chip repairs?
 
I had the exact same problem on my wifes' Envoy hood. It looked like a small dent almost. I used a small amount of clear and helped a bunch! I'm the only one that can tell where it is now.
 
EXACTLY:eek:



It now looks like a small dent instead of a paint chip. And now I'm worried even more since I have about 10 more chips to repair.



To anyone and everyone who can offer advice, techniques to repair this "ding/dent" effect and offer advice or techniques to avoid it in the future..........................:bow :bow :bow
 
Yes, please adivse. I have a number of very sloppy touch ups about a year old - done when I didn't know any better. I've been to a couple of body shops and been quoted any where from $1000 to $1800 to repair the damage I caused and repair the as yet untouched stone burises and chips.
 
I think your mistake was trying to sand the affected area only. Instead you must sand a larger area, say 1' X 1' surrounding the touch up. That way it wont get gouged.



Ryan
 
I thought the idea was to wet sand as small an area possible to avoid taking off more clearcoat than necessary:nixweiss .



It seems to me that if I had sanded a larger surface area, it would have created a "depression" in the reflection as opposed to a "ding".



Maybe some paint/touch-up pros can get in on this thread and educate us all :bow Certainly someone has encountered and "fixed" this type of problem before and can offer all of us advice on how to avoid this. Special techniques?? David Bynon.... you out there?:confused:
 
:confused: :(



Perhaps this question should be posted to "Autopia University" :rolleyes:



Looks like I've discovered a question that can't be answered or perhaps the right autopians have not read this thread.:nixweiss
 
Well, you may disagree with my opinion on this, but here's a take from someone that's been color sanding for 20 years;



You can't wetsand specific small spots more than a pass or 2 (with the paper) without encoutering this. You will notice "cratering" or a slight depression if you work a while at leveling the touch up, ESPECIALLY on black or dark colors. The human eye is not a good indicator on judging just how much you can sand an eraser-sized paint touch up in order for it to be level to the surrounding paint-WHILE you're doing it. It sure is after it's buffed out and seen in contrast though! You have to spread out your blocking to the surrounding area, sometimes as much as a 1/2 foot or more, in order to blend it and also to spread out the way you are cutting out the orange peel-otherwise your touched up spot will also be crystal clear flat and 2 inches away you'll have oem orange peel, making the spot even more conspicuous that way. One thing you NEVER want to do is use your finger behind the paper in one spot. You WILL see the mark.



If you are cautious and block it flat using perpindicular /opposite(45 degree angles) passes with a foam block behind it, you can effectively eliminate any wavy visual effects afterwards, while blending down the orange peel and the spot(s) at the same time. It isn't "easy" per se, but it's also not hard once you have some time and experience at it.



I learned many years ago, on a black car ( not my T-Bird SC), that spending even a small amount of time on a small spot will reward you with an eye catching indent after it's buffed out. I had to repaint the panel in fact. Learning the hard way is the best education sometimes.



I have NEVER experienced it again, simply because I learned to always block the surrounding area and feather it out beyond the repaired area. Yes, you will be removing good paint to a degree, but if you're careful it will be ~ 1/10th of a mil and that's fine. Let's face it though-the paint's already damaged if you're touching up chips, you have to accept that what you're attempting is a stopgap between perfection and a repaint, so...even if you're removing a little bit more of the surrounding paint for it to look correct, it's the price you must pay in order to not see small indents where you have sanded those touch ups.



Most of the wetsanding results are contingent upon how well you've built the touch up, and this too takes practice, in order to allow the least amount of sanding necessary. It's an art and a skill that takes time.



Just one man's take, FWIW.



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Thanks Guitarman, and as promised..........:bow :bow :bow



For better or worse, this is the type of information and experience I wanted to hear. Is there a special type of foam block that will shape to the contour of the panel when sanding?

I've searched the auto supply shops (Pep Boys, Autozone) but can't find anything.



Also, would it be possible to fix these "craters/dings" by applying a couple of coats of clearcoat touch-up and lightly resanding?

Or do you think I'll be making a bad situation worse?



Your expertise is appreciated....as well as everyone else who wants to jump in on this :xyxthumbs
 
In answer to the foam/sponge sanding block query( I use the 3M sponge block), I'm surprised you can't find one locally near you, because Pep Boys, Auto Zone etc. carry them here. But I found this if you want to order online;



http://products3.3m.com/catalog/us/...eisure_3_0/command_AbcPageHandler/output_html



They are only around $3-4.

They pads/blocks are abrasive (in various grits ) themselves, however, I primarily use them as a backing pad for color sanding. Just wrap the paper around them, making sure you fold the side edges of the paper over itself so there aren't any factory edges of the sandpaper showing on the bottom/sides of the block. If you don't do this, the factory edges will gouge into the paint while sanding and cause deep scratches , sometimes impossible to remove.



On the question regarding adding some clear to the touched up areas. Well, generally no, but it depends on how bad the depressions are, how you approach it and what you use, and how good you are. Firstly, shaker cans (the kind you buy in parts stores) of clear are almost always uncatalyzed (no harderner) lacquer based paints. You can't spray lacquer over enamel (which almost all oem finishes are) without the possibility of a chemical reaction, i.e. lifting, wrinkling etc. So remember that before you think you want to spray some Dupli-Color clear over your oem paint without using an acrylic sealer first. If you ever buy shaker cans of touch up paint, look for enamel only. They will still be uncatalyzed though-so they will forever be air drying (dry to touch, but not chemically), and not very durable.



Now, if you bought a pint of clear urethane enamel and activator, and had a compressor and spray gun, and wet sanded the area with ~800 grit till it was leveled better, you might still see the depressions unless you were really effective at blocking it flat prior, and that would be risky since to do it , you might wind up going through to the basecoat in spots to really flatten it out. It's tricky and difficult to say, because painters always spray a "guide coat" then block sand with a rigid rubber block, so they can see where the depressions are, then work the area some more till they are certain it's flat. Just spraying over the existing depressions with more clear isn't the best approach because-the new clear will just follow the same surface patterns that exist. Now, if you sprayed enough coats of clear, and could block it down flat, you might solve them if they weren't that deep.



Sorry this is long, but it's a complicated process and differing variables always enter into how you do it.



If you were to take it to a shop, they would likely block the whole area flat with ~320-400 grit, blend in color to only that affected area, then wetsand the entire panel with ~800 and clear the entire panel. That's how it's generally done.



It IS amazing though, that ~3/10 to 5/10 of a mil of paint removed in one spot can be so visually obvious to the surrounding area. The total amount of clear on your car is the width of a baby's hair (~50 microns or ~2 MILS), and we're only talking about 1/4th of that or less in these cases where a bit has been sanded down. Amazing indeed.
 
Hello there Guitarman, may i ask what you mean by folding the factory edges ? I have in mind 3M's 2000-3000 grit sanding strips, but don't see any edges though.....maybe you simply mean that one has to fold both the right and left side of the strip before using it, that s the only thing i can see at present.......but maybe something slips me ? :o





Oh by the way, i have been to couple of paintshop and they refuse to touch up the fron end of my hood (it s got a few chips, but really small ones though) they say they have to repaint the hole panel.....it s either they know their stuff and know for a fact that they wont be able to match those chip repairs to the surrounding paint, or they just feel lazy and prefer to go to the less complicated solution..........im sure you can help clear this up, since you re in the trade if im correct.



Best regards Guitarman, and by the way your thunderbird is just breathtakingly stunning !:xyxthumbs
 
FWIW, I'm a pro detailer not a pro painter, but my personal background is in restoring /fixing cars and trucks, and painting them myself on many occasions( My t-Bird SC for instance). I have painted in the neighborhood of ~13 whole vehicles, some of show quality, and been around body shops and the people that work in them, most of my adult life. Not an "expert" per se, I sure don't know everything about every paint and body product and repair, but I do know the basics of painting, blending, and bodywork, and have done all or some to a certain extent.



That said, here's what I mean on the wet sandpaper;



If you buy the 9inch sheets (full sheets), place the sheet face down (abrasive side down) and put the sponge block on it so that you have about 1/2 inch to 1 inch of sandpaper on EACH side of the block. In other words, if the sponge block is 3 " wide, cut the sandpaper to about4 inches wide, then FOLD those edges on the side of the block up UNDER the block. Now you have a rolled sandpaper EDGE where the side of the block hits the paint surface, instead of the factory sandpaper edge. Just think of it like this; If your hand can get a paper cut from the side of the sandpaper with just the bare factory edge, SO CAN your paint. You want to have a folded over edge(more rounded) along there.



Even if you buy wet sandpaper in the pre-cut 3 3/4 inch wide size (the solo sheets designed for rubber or sponge blocks ) you will need to fold the side edges over themselves and under the block.



Trust me, you WILL freak when you see the side cuts /scratches you put into your paint from a factory paper edge.



Make sense? Let me know if I've explained it properly, because it isn't always easy to get across with text.



As far as your hood and the paint shop, well, if it's a clearcoat on there , they will have to repaint the entire hood even if they blend in new color to that one area, it's just a question of whether they will scuff the entire hood, respray the basecoat over the whole thing, and reclear the whole thing OR , sand the chipped area, blend base color ONLY in that spot, and then reclear the entire hood. Either way, they WILL have to spray clear over the whole thing. It's probably just easier and less of a hassle for them to do the entire basecoat/clearcoat thing than to spot blend it and reclear. Every shop is different, and it all comes down to time = $$$ and what they percieve as being easier for them. Be aware though, if it's a metallic or pearlescent basecoat/ midcoat, and they just reshoot the entire hood with color, it *MAY* not match the fenders etc. This is why, I would probably try to BLEND the base in that one spot out onto the rest of the hood then reclear the panel. That way, your color match is blending in with the hood itself, and not up against the fenders, where, if it's slightly off in tone, you will surely see it obviously.



Hope this helps. Best of luck.
 
Yes it does make a lot of sense, and yes your explanation is pretty clear to me now ;) Yet one thing remains unclear.....you said you used the 3M block, and although the block per se is abrasive, you use it as a backing plate/support for your own sand paper, so far i get it, but tell me, once the edges are folded up under the block, how does the wet sandpaper hold to the block when you sand down a repair, as it sounds to me like there isnt much for your finger to get a grip on once the sides are folded up under the block............not challenging your technique in any way here, quite the contrary in fact, as i know you know far more than i do, and most especially have way more exerience than i do in the field, so i ask so i can do my own repair properly :D



Oh come to that ! today i filled some touch ups on my girlfriend's ride, i'll detail every step i took so you can correct me if mistaken or if technique can be improved some : first two days ago i washed and clayed the car, so i can clearly see nicks in the paint instead of mistaking em for loose dirt on the surface, then today, i went around the car mapping chips and scratch on some pics of left and right side along with fron end, so i remember where they are, then i proceeded to fill em chips.....what i did is : i have a nick sander so i used it to clean the ones that were large enough for the nicksander to fit in it(as i didnt want to sand too much outside the chips. Some i didnt use the nicksander cause they were way too tiny for it to fit in it. Then, i degreased them using isopropyl alcohol with a swab, let em dry(which was short as isopropyl alcohol evaporates in no time), then cut a matchstick to a 45 degree angle(tried wooden toothpicks but didnt like the capillary action on em) dipped the match about 1.5 milimeter in the factory coded paint i had done at a paintshop i trust a lot, then dabbed some of it into the chipped area........some area were so small that it produced a small blob instantly the first time, so i was kinda wondering if i had done it right, but later told myself that the chip is so small that it s almost normal for the paint to blob on the first time. Some larger chip i did have to apply many light coats, to slightly go over the surrounding paint, then since the temperature outside was not much above 60 degrees , i used a hair dryer to make sure proper bonding of the paint, then waited one hour approx. between light coats.



Now what i still have to do is wait 24 hours, sand them down, apply medium grit compound(3M rubbing compound) then swirl mark remover, 3M also(5937 more accurately). I had in mind to use 2000 grit wet sandpaper, but not sure anymore, since i have never done it and that clear is sooooo thin, i think i'll pick some 3000 grit instead of the latter. Now that is where you ccan graetly help me Guitarman, as the sanding down thingy is tricky stuff, and once done one cant put meterial back onto the surface(at least without shelling some dough lol). Would you be so kind as to be my mentor for this procedure :D Since im a detail guy, i know it s in the detail, that is success, as well as in experience, so could you outline how i should go about it once i get to the sanding step ? I'd really want to do it right........you should know that im veryyyyyy meticulous by nature, yet i prefer being guided through it by someone who knows his stuff, you in this case.



i appreciate your helping me, i want you to know that.



take care



P.S. is the hairdryer thing a good idea for when temperature is about ~ 60 farenheit ?



:wavey
 
I should've mentioned that you want to wrap the ends of the paper up over the front and back of the block, where it will be under your hand grip. Wish I had pics. BTW, this isn't "my" way of doing it- not something I came up with...this is what I learned from a pro many years ago, and generally how it's done.



With a rubber sanding block, it's a bit easier because they have "flaps" at the ends to tuck the paper under and hold it secure and tight. But it works either way.
 
I'm more than happy to help Chip, that's why im here. I try to help only in the topics in which I have the most experience, because there are plenty of other smart people here that know more about other things and products than I. But I have done a ton of colorsanding throughout the years, no 'bout a 'doubt it.



There are other wetsanding articles available at Autopia and around the web( most are very good too), but here's my POV on the topic , from a Thunderbird BBS. Let me know if you have any questions.



"Guitarman" AKA "onequiksc" on this site;



http://pub29.ezboard.com/fthunderbirdscenthusiastclubfrm13.showMessage?topicID=129.topic



Dan H
 
Ok, ive read it all and must say your explanation is real good !! It shows you've done it numerous times, as you describe every steps with a much clarity.



Now you say that one attempting to remove orange peel from OEM paint night only need to do 5-6 passes, then you're skating on thin ice or thin paint actually ;), i guess that is using 2000 grit wet sandpaper, right ? So the nicks i have filled a bit above surrounding paint would prolly need like what 5 passes before it s level ? I just wantto have a good idea of when i should be EXTRA cautious. I guess sanding nicks(chips) i will have to use this X pattern, right ? And come to think of it, the sanding blocks i should use for nicks and scratches, should they be standard size blocks ? and should i only sand the chip or sand a larger area for it to more easily blend and not produce any indent ? If so, let's assume a chip 1/4 '' square(as i have one, and the rest are tiny ones) how large around should i wetsand for this 1/4 '' square chip ? (this will give me a good idea for the rest).



when using compound to polish it afterwards, how large an area should i polish around, still for that 1/4'' square chip ?



take care



Mark:xyxthumbs
 
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