Wet Sanding. Dos and Don'ts?

[Cupra_UK]

My LCR has spent most of its life on motorways. A result of which it has inherited ample stone chips.

I've read a little bit about touching up (with paint that is) wet sanding and polishing. Some of the end pictures look great but the process pictures show a haze in the lacquer (I assume) which is then polished out?

Has anyone here tried this technique on Black? What are the dos and don'ts of using this? How easy is it to ruin the paint? And what products would you recommend?

 

[Jace]

I've done a little on my old golf, its not too hard if you

A: Have the correct polishes,

B: The right grade of W&D,

C; Have rotary polisher, PC is hard work but possible

D; Have nerves of steel


Tim @ Clean Your Car stocks the Menzerna polishes & the Meguiars W&D you'll need.

 

[Daffy]

Same as Jace pretty much although have done it on a few cars. The more you do the better you get. Dark colours are much easier to do than light colours like silvers and white.

 

[Ninja]

if you've never done anything like this before i would suggest trying on something before your car!! Maybe pick up a crappy spoiler or something from a scrappy and practice on that ?

 

[Cupra_UK]

I intend to practice it on the family run-about. It seems like a simple enough process but thought I would find out about the pit falls the easy way?!

 

[fatherted22]

have tried touching up small stone chips, then rubbing them flat with 3000 grade, and then Meguiars Scratch X, before polishing. A lot of elbow grease but worked really well.

 

[fatherted22]

colour was Platinum grey - don't know if that made it easier to work with ?

 

[Cupra_UK]

My car is black. I've read that darker colours generally are easier to work with.

I've tried touch up paint and Super resin polish previously. This works too.

Just never tried wet sanding and am a little worried about not being able to get the lacquer clear again.

 

[fatherted22]

worked ok for me, but did panic a bit at the results of the wet sanding before I used the scratch X.

used plenty of water when sanding as the 3000 grit clogged up very quickly.

 

[Cupra_UK]

I have A LOT of stone chips on my bonnet so I guess even if I ruin it, it’s not that big a deal.

In fact I have so many stone chips, I plan to do the bonnet in three stages/ days. Left, centre, right.

On DW, fairy liquid is recommended as lub whist sanding. But how much of this to use? Surely when it foams up you can't see the area you're working on?

 

[fatherted22]

Ah ! I had only about 6 !

 

[Daffy]

You can use fairy or car shampoo. I use Last Touch but mix it in the bucket that the paper soaks in as well. It doesn't foam much and you don't rub that much just enough to flat it off. You really need a machine polisher to get rid of the sanding marks, Scratch X and the like will do it but if you are doing the whole front end this is a) take a long time b) take a very long time and c) hurt. You will also get a better finish.

 

[Cupra_UK]

I think that's a very valid point. A friend of mine has a machine polisher and I have a steady hand. I’ve read a fair few threads on DW about what not to do with machine polishers so it should be ok.

Daffy what would you recommend to clean the stone chips out with before using touch-up paint? Also would you suggest leaving the paint over night or just until it looks/ feels dry?

 

[Daffy]

I would use something like Tardis from Autosmart if you can find some or a strong solution of APC. Alternatively you could just wash it with washing up liquid if you don't have anything else, again fairly strong solution but make sure you don't let it sit on the car for too long and the paintwork is cool also a thorough rinse afterwards. May need to do it a couple of times with the washing up liquid method and make sure you re-apply wax to the whole car as it will strip it off.
I would leave overnight if you can in a garage would be ideal. Use a toothpick or cocktail stick to apply the paint as well it is much easier than the brushes it comes with.

 

[Willie]

Make sure when you do this that you fill the chip up to above the top of the chip as the solvents flash off when drying and reduce the amount of paint in the hole.
Does your friend have a paint thickness gauge?
If you can get a hold of one it would be worht while to monitor then amount of surrounding paint your removing, its very difficult to tell if you don't have one. You don't want the first sign of removing too much to be the primer showing through.
Are you going for the pencile top method or just a stiff pad?
What sort of machine has your mate, make sure he's got spot pads aswell to reduce the amount of area covered and reduce the time taken to get rid of scratches/marring.
You'll need a good range of polishes too, as suggested above Menzerna range will cover everything

 

[Daffy]

If you use 4 inch spot pads you will have to be even more careful as they generate more heat and you risk burning the paint. 6 inch pads will be fine unless you have some tight areas that you need to get into.

 

[Cupra_UK]

Thanks for the tips guys. Didn’t really think about it before but most of it seems obvious now.

I actually find that touch-up pens Halfords do are perfect for filling chips. The nib is very thin and as long as it's kept clean you can easily determine how much comes out. Colour match is a different issue, although my car is a non metallic black so it shouldn’t be too far out.

I don’t have access to a paint thickness gauge but I've been thinking about investing in one of these. It's a great tool for when you're buying a car too If you suspect the car has been repainted.

I don’t know what machine he has as he just mentioned it in passing but if it's not a very good one, I won't use it. I'll probably invest in a Silverline one if need be.

Pencil top method? I thought the pencil method involved wrapping some paper round the pencil? Is there a general preference of one over the other? Any particular reason?

3M or Menzerna is what I've been recommended. Will get one of those.

 

[Willie]

Each to their own with method, whatever your happy with.
The pencil method is as you described, the only person i read who did this had problems so don't know if its advisable but if you do get it right atleast your not removing any surrounding paint
I'm sure Daffy will have sme suggestions for you