Uni-grit usage questions!

[wifehatescar]

I just bought some unigrit 2000 and 3000 and the foam backing pad for my first wetsanding session. The car's paint can be found here in a Detail City post:

http://detailcity.com/forums/showthread.php?s=&threadid=6178

What paper would you start with first? Keep in mind this was a cheap, bad paint job that was done.

Also, I was wondering how YOU wrap the paper around the foam block? I've heard the egde of the paper can cut too deep and you are suppose to fold all edges to prevent this. What this means is you take the paper, fold 2 edges on top of the themselves by 1", the fold the other 2 edges over two sides of the foam block. This way none of the "ends" of the paper are touching the paint.

I called the Meg's tech line and they said just wrap the paper around the foam 1 1/2 times and go at it (i.e. the edge of the paper will be in contact with the paint)

Fianlly, how many hours will this job take me (I have estimated 10-12). Any other tips?

Thanks

Steve

[Mike Phillips]

Hi wifehatescar,

Welcome to Meguiar's Online!

You ask a very good question, give me a moment to type up some helpful tips and techniques.



Mike

[wifehatescar]

Thanks! Just what I need another detailing forum to visit daily

I shall await your response, feel free to check out the Detail City thread too, I had a dozen or so responses and bits of advice.

[Mike Phillips]

I can't help you with the forum dilemma, I have the same problem!


Tips for hand wet-sanding

There are two ways to fold your paper around the sanding block.

1) Fold you half-sheet of sanding paper in half length wise, and then hold this around your sanding block. Mike Pennington shows this method in our how-to video,

How To Remove Paint Defects


2) The other way is to start by wrapping your sanding block with your half-sheet of sanding paper and continue until you have completely folded the paper around the sanding block.

Either way will work, and from my experience the differences in end-results cannot be distinguished. This means it comes down to personal preference.

Personally, I prefer the second method. After sanding with one portion of the sanding paper, (till I feel it has become ineffective), I then re-fold the sanding paper around the sanding block to expose a fresh portion of the sanding paper.

As far as you concern about the edges of the paper instilling deeper scratches while your sanding, two things,

1) Because with any method of wrapping your sanding paper around the sanding block you're going to have sand paper laying across the edge, it is impossible to avoid.

2) The best way to reduce the potential for deeper sanding marks instilled from the sides of your sanding block is to use a sanding block with some cushion to it, (like Meguiar's Sanding Backing Pad). The extra thickness enable you to control your sanding marks by allowing you to push more pressure to the center of the pad, versus the outside edges. It takes a little experience and technique and the right way to hold the pad, but if you do a little experimenting, you will see what I mean.

Sanding Backing Pad



Mike

[wifehatescar]

Thanks.
I think you mis-understood a bit though, I'm, not worried about the foam backplate touching the paint, I'm worried about the edge of the unigrit paper touch the paint. With both methods youy listed, this would be the case. Should I worry about this?

Also, any comment on the condition of the paint in the pictures in the link I provided?

[Mike Phillips]

Tips & Techniques for Hand Wet-Sanding

First some tips, then an admonishment

• Always sand in one direction, don't sand in circles.
  
• Make 6-8 strokes at one time and then check you results. If your trying to remove orange peel, squeegee the surface you have sanded using a second Meguiar's E-7200 backing pad, this will make it easy to see how flat your sanded area is.
  
• Use some car wash soap in your sanding water. This will help prevent your sanding paper from loading up and also lubricate the surface to insure smoothing sanding action.

An admonishment,

Before sanding down the entire car, or even on half of the hood, first do a Test Spot.

Sand just one small area, and then try to remove your sanding marks using your choice of buffing pad, (wool or foam), with your choice of chemical, (Typically a compound), with your rotary buffer at around the 1500 rpm setting.

See if you can completely remove all of the sanding marks to one small area before sanding down the entire car.

If you cannot remove the sanding marks on one small area, you will not be able to remove them over the entire car.

Mike

[Mike Phillips]

Originally posted by wifehatescar
Thanks.
I think you mis-understood a bit though, I'm, not worried about the foam backplate touching the paint, I'm worried about the edge of the unigrit paper touch the paint. With both methods you listed, this would be the case. Should I worry about this?

Also, any comment on the condition of the paint in the pictures in the link I provided?

I understood you completely. You're worried about where the sanding paper that is against the edge of the backing pad putting in deeper scratches because there is usually more force in on the edges?

Correct?

Mike

[DETLMAN]

I always start with the edge of the paper down toward the finish and then wrap the paper around so that the first edge is covered and the only exposed edge is on the top, held by my hand.

I hope you understand what I mean its a little hard to explain.

[Mike Phillips]

Hi Steve

STOP!

If you haven't already started sanding, I would stop.

I just read the thread on DC and there is a lot of great advice over there, but here is something I think everyone missed.

This paint is a single stage that is fully cured. Two thought that cross my mind are these,

1) Black single stage paint are usually the softest paint there is to work on, that is because of the pigment type which generally Carbon Black. Because this type of paint is soft, it will be easy to sand and it should be easy to remove your sanding marks out of. But, it will be easy to sand to far, and even easier to buff to far and burn through high points and thin areas

2) Even though single stage black paint is usually the softest paint there is to wet sand, cut and buff, you never know until you do a test spot. The time to have sanded and buffed this paint job was the day after it was painted, not two years later. As the paint cures, it becomes harder, and thus more difficult to remove your sanding marks from.

Do the test spot. Inspect the results in different light. Make sure your have completely remove all of the sanding marks, and any Tracers. Tracers will haunt you on this finish.

I don't know what you're charging for this job, but I would walk away from it if it's not close to or over a low of $800.00 and a high of $1500.00

But then, I wouldn't do it. As soon as you burn through in one area, it's all over. A repaint will be needed to correct the problem.

Been there, done that, won't do it again.

Mike

[Mike Phillips]

Originally posted by DETLMAN
I always start with the edge of the paper down toward the finish and then wrap the paper around so that the first edge is covered and the only exposed edge is on the top, held by my hand.

I hope you understand what I mean its a little hard to explain.

Exactly, I think Brian explains it better, fold your paper around the backing plate in such a way that no edge of the paper comes into contact with the paint. You will always have an edge of the backing pad, against the finish.

(I kind of thought not having the edge of the paper against the finish was a given, my mistake).

If anyone likes, I'll go wrap some Meguiar's Finishing paper around a backing pad and post it to be sure.

(Because Meguiar's papers are made using Unigrit technology, we don't call them Sanding papers, but Finishing papers instead. The results after sanding with our finishing papers look like the paint is just dull, not sanded.)

Mike

[db_abz]

Originally posted by Mike Phillips
You're worried about where the sanding paper that is against the edge of the backing pad putting in deeper scratches because there is usually more force in on the edges?

Mike

Nearly Mike,
what he means is that the actual edges of the paper will cut more into the paint than any other part of the paper, due to the fact that's there's a ragged edge to the paper. This will happen even if the paper's edges are protruding out from the edge of the block. I read an excellent article that expained it all (pity I can't remember where!!). The fix is to fold the paper in at the edges so that there's a rounded edge to the paper.

Far too many uses of the word "edge" but I can't think of an appropriate alternative, hope this helps.
Dave

[wifehatescar]

ad_abz

That is exactly what I am afraid of, the ragged edge of the paper.
I will try to fold it so that is not an issue.

Today I am about to do only a test spot. Also, I'm going to start with 3000 and try to not even use the 2000. To be honest, I may try to rotary buff first to see what improvement it makes. I will be as careful as possible. I plan to charge ~$450 for in my estimation 15 hrs of work. If I only use 3000 grit and the car is not a showcar, I hope to be ok.

I will make a post tonight (with pics) of the test spot.

[wifehatescar]

Originally posted by Mike Phillips

1) Black single stage paint are usually the softest paint there is to work on, that is because of the pigment type which generally Carbon Black. Because this type of paint is soft, it will be easy to sand and it should be easy to remove your sanding marks out of. But, it will be easy to sand to far, and even easier to buff to far and burn through high points and thin areas

2) Even though single stage black paint is usually the softest paint there is to wet sand, cut and buff, you never know until you do a test spot. The time to have sanded and buffed this paint job was the day after it was painted, not two years later. As the paint cures, it becomes harder, and thus more difficult to remove your sanding marks from.
Mike

PS- I understand what you are saying but point 1 and 2 seem to conflict. First you say it is super soft in 1) then you say it is hard in 2)
Anyway, off to test spot I go!!!!

[Mike Phillips]

Originally posted by wifehatescar
PS- I understand what you are saying but point 1 and 2 seem to conflict. First you say it is super soft in 1) then you say it is hard in 2)
Anyway, off to test spot I go!!!!

Actually, they don't conflict.

Paint is it's softest when it is freshly applied. It gets harder as it cures and with time. Black single stage paint is a soft paint, key word here is "Usually", not always, and it is it's softest when it is freshly sprayed.

You say this paint is 2-years old, it may be soft paint, but it was a lot softer 2-years ago.

Best of luck.

Mike

[Mike Phillips]

Originally posted by db_abz
Nearly Mike,
what he means is that the actual edges of the paper will cut more into the paint than any other part of the paper, due to the fact that's there's a ragged edge to the paper. This will happen even if the paper's edges are protruding out from the edge of the block. I read an excellent article that explained it all (pity I can't remember where!!). The fix is to fold the paper in at the edges so that there's a rounded edge to the paper.

Far too many uses of the word "edge" but I can't think of an appropriate alternative, hope this helps.
Dave

I did misunderstand what he meant, I kind of took it for granted no one would sand with the edge of the sanding paper in contact with the finish. My mistake.

Whichever method you use to wrap you sanding paper around the backing pad, when you sand on the finish, make sure none of the edges of the sanding paper are in direct contact with the finish. The edges should be on the opposite side, away from the surface. If you using the method I listed first, where you fold the paper in half, then when you wrap this around your backing pad, it won't be long enough to allow an edge to come into contact with your car's finish and instead they will stick up in the air because they paper is stiff enough it will not easily fold over and lay down against the backing pad.

Where's my camera?


Is that better?

Mike