Sand scratches still?

6

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Ok guys I've wet sanded starting with 1000 then 1500 then 2000 then 2500 all done by hand..after buffing with all three stages of 3m compound I can still see wet sanding scratches...the local supply guy said to sand only to 2000 so I did but saw scratches so I went on to 2500 and am still seeing some...I've tried buffing a bit more with the compound, changing speeds etc.. and still with a 500 watt light pointed directly at it see scratches..what am I doing wrong? I'm fine living with it to an extent but want to know how to correct it..thanks guys
 
either in the standing stage or buffing stage you are moving on to the next step before you fully get out the scratches from the previous one. when you sanding with 1500 you need to get every 1000 grit scratch out before you goto 2000. when doing 2000 you need to get all the 1500 out before moving on.......an so on
 
What Jim said plus here is a copy of a post i made yesterday and to add, ALL scratches must be gone BEFORE you go to next finer compound.
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Sounds like you did not buff out the scratches but filled them with glaze and the glaze will wear off in week or two.
All compounds have glaze as a lubricant but as you go to finer compounds they have more.

Make sure you have a cutting buffing pad to match the 1st cut compound.---WRONG pad is number one cause of this problem and speed the second cause.
Cut back on the compound and on first cut up the speed of buff, slow down as you go to finer compounds and finer pads.
 
I have problems with 3m 2500 sleeves having defects or something. They will actually scratch worse than the 2000 3m. It's random like I'm getting rejects. Some sleeves will never do it and if I get one that does I pitch it because they all seem to have it. Almost like defects that have some randon courser pebbles in the paper. I've removed that step from my process as I've had a lot of problems over the years. I just have to hit it harder with 3000/5000 trizacts to cut the 2000 grit straight line marks.

In my experience using foam pads like trizacts are the only thing that is gonna remove the straight line 2000 grit marks. Otherwise the surface is shiney and looks good but under the florescents you can see subtle straight line marks.

I always criss cross my grits also. It helps show that you have removed the previous grit. Say 1000 grit is horizontal and then 1500 is vertical and then 2000 is horizontal again. Wipe the panel clean between grits and look at the surface really close and you will see if you removed the previous grit.

1200 grit really helps remove the 1000 quicker. One more step but it seems to speed it up a little. 1000 to 1500 seems to be to much of a jump. 1500 to 2000 doesn't seem to be a problem.
 
Lots of variables and it's something I struggle with as well. But one thing I did realize is don't use junk sandpaper. Cough up the big bucks for the 3M. I've found cheap paper leaves gouges that are deeper that the grit they are supposed to be and the scratches will never come out because the more you sand, they more your scratching it.
 
Ok thanks guys I'll cut longer with each grit, I have the foam pads that color match the compounds but not so sure I like the foam with the first compound...also is Norton black ice good paper?
 
Also where should I go from here, I'm a bit scared if I keep cutting I'll cut through...
 
The black ice is a great wet paper, 1500 it flat or 2000 (whatever you have and get a wool pad for first cut.
 
I forgot to add that I also count each stroke. Each area gets consistent patterns and I average about 20-30 strokes per grit of paper to remove the previous grit marks.

Change paper often, your not saving yourself anything by milking a piece of paper.
 
What color is the topcoat? Maybe you can use a powder guide coat as a sanding guide. It's a great visual indicator and does not wash off when wet sanding.

Mike
 
MikeS;n82425 said:
What color is the topcoat? Maybe you can use a powder guide coat as a sanding guide. It's a great visual indicator and does not wash off when wet sanding.

Mike
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wouldn't do that, you want to keep everything as clean as possible no need to introduce contamination.
 
Keeping the powdered guide coat away from the edges easy enough so as not to leave any residue but as far as contamination goes, if you sand until the powdered guide coat is completely gone (which would surely indicate the scratches from the previous cut are gone) then there should be no contamination. That's how I do it anyway and it works for me.
 
Guide coats aren't going to show up those type of scratches. It would work for showing peel and level but not the micro scratches. Like Datec said in that stage you want everything CLEAN. Its just one of those things that takes some trial and error to know how much to sand until the previous grit scratches are gone. Like Brad said cross hatching grits then squeegeeing the water off and checking to see if the previous grit remains works good.
 
Color is Gulfstream aqua on a 68 mustang , these are very fine scratches that you really can't even see with normal garage lighting. Since I have buffed all three stages what would you guys suggest I do if I want them gone? If I started back over at say 2000 then watch to see if that will take them out, then finish with 2500? What really sucks is I felt like I was being very thorough through the whole process, I spent literally hours on every panel :)
 
Chris_Hamilton;n82433 said:
Guide coats aren't going to show up those type of scratches. It would work for showing peel and level but not the micro scratches. Like Datec said in that stage you want everything CLEAN. Its just one of those things that takes some trial and error to know how much to sand until the previous grit scratches are gone. Like Brad said cross hatching grits then squeegeeing the water off and checking to see if the previous grit remains works good.
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Hi Chris,

I agree with guide coat related to peel and level but from my experience when the dry coat is put onto, let's say 1000 grit, it is trapped inside those cuts even though we may not be able to see those fine lines, but the presence of the trapped powder indicates its still there. So the next grit, while removing the previous cut , will also remove the guide coat powder. I've even seen at times rogue single line cuts highlighted by the guide coat left behind so I get the opportunity to sand them out. What I don't guide coat however is the very last cut before polish this way I'm sure of no contamination. I also do cross cut as part of my method. I also remembering seeing a video on You Tube where a '55 Chevy (I think that was the year) was having its clear coat blocked and a guide coat was being used.

Mike
 
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