View Full Version : Deep Scratches using 2500?!

Nov 27th, 2005, 01:17 PM
I have been having nothing but problems when it comes to wet sanding/buffing my hood. I have recently painted a fiberglass hood for my mustang and having had troubles with the sanding/buffing process before I made sure I did things different this time. I went straight to using 2500 grit (meguiars unitgrit paper) and had a steady constant flow of water over my sanding area to remove any objects which could scratch the finish which get dislodged in the sanding process. I go to buff the hood and once most of the small scratches go away, I notice a decent amount of large (several inch long) scractches which appear deeper. I end up having to buff for an extremely long amount of time (with Diamond Cut) in one area in order to get the scratches to go away. I spent over 5 minutes just a couple of the countless deep scratches. Several issues here:

1. Why did they get there in the first place, especially when using such a light grit of paper?

2. Why wont they buff out?

3. (Not related to sanding per-say) - Why when I buff, are there minute scratches (circular patern probably from the buffer) which won't come out either? There scratches are MUCH smaller than the ones described above. Im betting its from the buffing process, not sanding.

A little background - My hood was painted several months ago, its black and although I did not bake it, it has been sitting in the sun as the mustang is my daily driver. I understand that if you dont buff soon after painting that the process becomes extremely more difficult.

Buffing Process Im Using: Diamond Cut --> Fine Cut Cleaner --> Swirl Remover (Never make it to this step because of the scratches)

Should I just go lay a couple more layers of clear on the hood and buff it soon after painting?

Any help would be much appreciated - I've already invested 15 hours into buffing this hood and its no where near where it needs to be - it looks pretty bad.

Thank you very much - Ryan

Nov 27th, 2005, 02:54 PM
You could be pushing down too hard. Just let the paper glide over the surface. If you have access to a DA, use the 3M Trizact system or the Mirka system. It may cost a lot but I think this is the way to go for wet sanding.

For bufffing out wet sanding I use:

#85/wool pad

Nov 27th, 2005, 07:17 PM
Did you soak the papers in water overnight BEFORE using??

Nov 27th, 2005, 08:27 PM
It's possible the deep scratches are from under the paint. If you don't lay enough paint down to fill the primer sanding marks they will show through the color layer...

What grit was your last sanding paper on the primer?

Nov 28th, 2005, 04:47 AM
I do question pushing down too hard, because trying to knock clearcoat down using strictly 2500 can be a daunting and tedious task. I did soak the papers however, thats actually how I stored my paper from the last time I used it.

As far as the primer, I last sanded the primer with 600 before I shot the paint. The clear looked fine before I sanded with the exception of the expected orangepeel, no scratches to be seen in the paint or in the color...

I have no objections to laying down more clear if that will make my life easier. Is this a route I should take or are there better solutions?

Also - when I used the diamond cut, I used the maroon maguiars pad, I also used that same type pad for the fine cut cleaner (two sets obviously, I didn't use the EXACT same pad).

Thx again for your help.

Mike Phillips
Nov 28th, 2005, 07:13 AM
It sounds like somehow you're getting loosed abrasive particles, or some type of dirt or contaminant trapped between your paper and the finish, this will instill the traces you are now dealing with.

#2500 grit paper is really too fine for what you're doing, at least to start with, to knock down the orange peel you usually want to start with #1500 grit or #2000 grit paper.

If you're looking for speed, go with the #1500 grit. Our Nikken papers use both Uniform grit particle size, but also use Uniform grit particle distribution over the entire sheet of paper whereas many automotive grade papers can be 60/40, 70/30, fill or somewhere around there. The point being is that because 100% of the sheet of paper is sanding, i.e. removing paint, you can usually step up a grit level in the Nikken brand and remove just as much paint as a competitors next grit level paper below our but leave a more shallow sanding mark pattern in the finish. The goal being to make the sanding marks easier and faster to buff out with less tracers and best of all, leaving more paint on the car.

If you have tracers at this point, it is usually faster to re-sand the area, or the individual tracer and then buff out your sanding marks.

As for product and pad combination, our M85 Diamond Cut Compound is formulated to work best with a wool pad, not a foam cutting pad and you will often times find M85 not working well with foam, so try it with a quality wool cutting pad.

Tracers are a nightmare and it sounds like you've done everything you can to prevent them. As another member suggested, make sure you're not pushing down to hard on your backing pad, you would be much better off to substitute a more aggressive paper and push lightly letting the paper do the work than to use a lighter grit paper and pushing down harder because it isn't performing to your expectations.

Nov 28th, 2005, 08:19 AM
I will try sanding the indivisual tracers and starting are a rougher grit and less pressure.

Is there any recomendation as far as which wool pad to use with the diamond cut? And is Diamond cut the right thing to use considering the paint has been sitting baking in the sun for the past couple months? I just feel in general that I am spending too much time buffing something - everytime I buff (and most of my experience is with hoods) it ends up taking hours upon hours upon hours... The actual buffing process seems to be taking way too long - this is however the first time that I've attempted to use anything more agressive than fine cut cleaner with the maroon pad.

- Ryan

Mike Phillips
Nov 28th, 2005, 08:24 AM
Any quality wool cutting pad should work just fine with M85, Meguiar's offers one that can probably be found at most PBE stores, part number W-4000

As far as buffing out paint this old that has been baking in the sun, depending upon the paint itself, it's probably fully cured and hardened by now thus sanding will be easy, removing sanding marks will be hard.

Most the time the sanding and buffing procedures should be performed sooner than later while the paint is still soft enough to buff out your sanding marks easily. As the paint hardens, removing sanding marks, (removing paint), will become more and more difficult.

What kind of window of time does the paint manufacture recommend for sanding and buffing?

Nov 28th, 2005, 08:40 AM
I used Transtar Clear VOC 2.1... To tell you the truth, i do not recall which exact version I used, but I know it was one of these two:




One of which claims its buffable in 2 hours.

Mike Phillips
Nov 28th, 2005, 08:48 AM
Usually sooner is better than later, most painters I know sand and buff within the next day or two...