# Wet sanding didn't work out like I planned!



## Blue (Sep 15, 2008)

Well I decided to have a little bash at wet sanding the other day and am not sure I've got it right yet!

I did a test patch on the boot lid of my E39, using 3000 grit wet and dry that was kept well soaked in CG Speed Wipe and lots of water. I went back and forth in one direction only.

Afterwards I polished with Menz IP on a Sonus SFX1 spot pad, finished up with the same polish on an SFX2 pad.

Out of the light it looks fine, but under bright sunlight I can still see loads of sanding marks in the clear coat, they are very fine, almost like uniform swirls, but they haven't shifted.

So, do I step the polishing up to a compound? I can probably get my hands on some G3 if I need to? Is it likely to be my technique that's wrong?

Likewise, does anyone near Sunderland have any experience of doing this successfully and want to lend me some expertise? I'll bring my own stuff 

I want to get this right before I attack the Z4 which has nigh on perfect paintwork, apart from the bonnet gouges that I am gradually filling with touch in paint ready for sanding!


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## Ultra (Feb 25, 2006)

Is this via DA or Rotary ?


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## Blue (Sep 15, 2008)

Sorry should have said, Rotary.

I was thinking that maybe even the IP on a spot pad doesn't have enough bite to cut into the BMW paint, the E39 is definitely old school where that's concerned!


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## Ultra (Feb 25, 2006)

3000 is lightweight is so just go over the area again in smaller sections at a slower pace :buffer: if that makes sense.


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## CraigQQ (Jan 20, 2011)

is it still a haze you can see ot is it a few deeper marks?

go back over it with the IP and sfx 1 pad in smaller sections(or use the spot pad)


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## Superspec (Feb 25, 2011)

I reckon they aren't sanding marks due to the paper. I bet they are marks caused by clumped clear coat...3000 grit should polish out no problem, even on BMW paint. 

Maybe pick up a 4000 Abralon pad - keep it very clean and then polish that.


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## Blue (Sep 15, 2008)

Will give it another bash then next weekend when I get a chance, just to clarify though, what do you mean by clumped clear coat Superspec?

The marks are quite defined rather than being a general haze Craig.

To clarify, I've hit it with the SFX1 Spot pad, probably making 8 - 10 passes.

Think I'll order new paper as well and give the 4000 a go!


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## planktom (Jun 15, 2011)

any pictures made ?


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## Blue (Sep 15, 2008)

I'm afraid I only have a phone cam and it's not going to pick the marks up under bright sunlight, essentially imagine some parallel (I sanded in one direction), straight, swirl marks. That's pretty much what they look like.

I'm wondering if I applied too much pressure to the sanding block, if they don't polish out then I'll try going again with very, very light pressure.


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## CraigQQ (Jan 20, 2011)

sounds like the clear coat dust was being caught up in the paper and dragging larger particles on the paint..

also if is cheap paper it might not be uniform grit size.

theres many factors that can influence this.


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## PugIain (Jun 28, 2006)

3000 should be easy to get out.I attacked mine with 2k and it polished out easy via DA with some megs 80.
Give it a wash and make sure its clean before you machine it again.


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## Superspec (Feb 25, 2011)

I don't know if you got this sorted by now but by clumped clear coat what I meant was the dust created by the clear coat clumping together and scratching into the surface. 

I had the same problem when wet sanding back filled in stone chips on my bonnet. I thought I was using plenty of water but turns out I wasn't. The paper was clogging and damaging the clear coat. It was a ***** to polish out!! I didn't have my Abralon discs then, I wish I had!!


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## wja96 (Jun 16, 2010)

When I did the wet sanding course at Shinerama we were told that wet sanding by machine was DA only. If that is correct (and why wouldn't it be?) then that may be part of your problem.


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## macmaw (Mar 5, 2007)

wja96 said:


> When I did the wet sanding course at Shinerama we were told that wet sanding by machine was DA only. If that is correct (and why wouldn't it be?) then that may be part of your problem.


He means he was polishing it afterwards with a rotary polisher, not sanding with one :buffer:


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## macmaw (Mar 5, 2007)

Blue said:


> ......I've hit it with the SFX1 Spot pad, probably making 8 - 10 passes.....


That's not really enough passes there & probably not working the polish fully.
Using the Zenith point technique & better still the plateu version of that, you should be spreading at speed 1, then make 2 passes at speed 2, then make 4 passes at speed 3, then make 4 passes at speed 4, then another 4 passes at speed 3 again, then another 2 passes at speed 2.
This should see your polish fully worked, but if it's not then make a few more passes at speed 3 & 4 or start again use a bit less polish. You could actually need nearer 20 passes in total. 
That's just one hit, you might need two hits plus refining after that with something like Final Finish on a finishing or light polishing pad.
Also very important to have a PTG to hand to see how much you remove between sanding & polishing. 
The BMW paint is extremely hard & my E39 is giving me a good old challenge too as we speak, & it's mostly only light swirling. 
I also have a few RIDs & some stone chips which I'm going to fill & sand later. 
HTH


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## Aaran (Sep 18, 2007)

agree with the above, you MUST keep the surface clean, when i wet sand a painted car i actually do away with a bucket and just put a hose on spray so it constantly just runs water over what i am sanding.

and again use a very good brand, megs, 3M, horse etc.

all it takes is one grain of dust/grit between the paper and surface to put deep scratches into it. when you re-sand it this time go the exact opposite way (if you were going up and down then go side to side) let the paper do the work and always use a hard sanding block)


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## CraigQQ (Jan 20, 2011)

Aaran said:


> agree with the above, you MUST keep the surface clean, when i wet sand a painted car i actually do away with a bucket and just put a hose on spray so it constantly just runs water over what i am sanding.
> 
> and again use a very good brand, megs, 3M, horse etc.
> 
> all it takes is one grain of dust/grit between the paper and surface to put deep scratches into it. when you re-sand it this time go the exact opposite way (if you were going up and down then go side to side) let the paper do the work and *always use a hard sanding block*)


i completely disagree with the last part of this..
i would never use a hard sanding block to wet sand anything..
this will cause uneven areas, and flat spots compared to a softer sanding block such as the meguiars foam blocks will not bend to curves and give a much more even pressure on the paper, the foam block aswell, absorbing some of the pressure put on (this is a good thing for a newbie, who might be tempted to push too hard)

kelly, master of the wet sand in some of his tips that are scattered throughout his posts, even include using the palm of your hand as a block as your more likely to feel the grit ect inbetween the paper and paint.
but I haven't tried this, and might be a bit more skill necessary to maintain even pressure (ofcourse im sure kelly has all the skill he needs :lol

also a running hose wont be a good idea if you are machine sanding :lol: 
run into problems there lol...


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## Mirror Finish Details (Aug 21, 2008)

CraigQQ said:


> i completely disagree with the last part of this..
> i would never use a hard sanding block to wet sand anything..
> this will cause uneven areas, and flat spots compared to a softer sanding block such as the meguiars foam blocks will not bend to curves and give a much more even pressure on the paper, the foam block aswell, absorbing some of the pressure put on (this is a good thing for a newbie, who might be tempted to push too hard)
> 
> ...


Cheers Craig

There are a lot of rules for wet sanding and a lot of rules to bend.

I learnt my trade at Rolls Royce in Crewe and really there is no hard and fast rule. I often sand with no block round curved areas, you just get to feel the knack over time. Always use a block on flat panels.

Ideally you will use a soft foam block for hand blocking, using 2000, 2500, 3000 then ideally 4000 grit paper. Plenty of lube in the bucket and keep the papers wet. using a hose is useless.

For DA as I demonstrate at our courses we usually use 2000 then 4000 grit pads. They hold a hell of a lot of water and you can usually sand a whole door before putting them back in the bucket. But I prefer to sand by hand and charge accordingly.

If the OP has a problem polishing out sanding marks then to be blunt he has done it wrong. In 30 odd years wet flatting cars i have never had a peice of grit stick to the paper.

Sanding marks are easier to remove if properly sanded than hard compounding.

I reckon Kelly would say the same.


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## CraigQQ (Jan 20, 2011)

Mirror Finish said:


> Cheers Craig
> 
> There are a lot of rules for wet sanding and a lot of rules to bend.
> 
> ...


sorry steve didn't mean to leave your name out the post :thumb:
i thought the hose might be useless but without knowledge such as yours couldn't put my name to that statement as no evidence/experience to back it up.

glad you agree with what i said lol.. makes me feel better about it :lol:

kelly and yourself give great advice on these threads..
plenty of advice from the forum but myself personally i was given most of my tips and techniques from a non supporter(atm) of the forum, who isn't specifically a detailer, but highly skilled in this field.. (most probably know who this is as i have given him the thanks/recognition for his help before, but i wont name him or his inbox will be full in 3 minutes with requests for info :lol


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## caledonia (Sep 13, 2008)

Mirror Finish said:


> Cheers Craig
> 
> There are a lot of rules for wet sanding and a lot of rules to bend.
> 
> ...


I do not mean to be confrontation here. But how do you explain this then. Either missed completely or not removed during polishing.

http://i182.photobucket.com/albums/x195/whitelady-2007/VW Golf 4 motion/P1060361.jpg


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## caledonia (Sep 13, 2008)

Mirror Finish said:


> Phew, I thought you were talking about one of my jobs then Gordon.....or do you think this is me????


Unfortunately yes.
But lets not go there.


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