Removing paint

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Hammond
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Removing paint

#1 Post by Hammond » Wed Aug 14, 2019 4:41 pm

EDITED

I'm going to strip back all the paint off my 400 bubble bumper to the grey plastic in preparation to getting it resprayed.

Any tips the best way to do it?

Wire wool? Nitromors or similar?
Last edited by Hammond on Thu Aug 15, 2019 4:58 pm, edited 1 time in total.
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Johnny 216GSi
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Re: Removing paint

#2 Post by Johnny 216GSi » Wed Aug 14, 2019 8:05 pm

Was that a misspelling and you meant "black paint" ??

You know it isn't strictly necessary - if you bought some wet and dry abrasive paper from Halfords, etc. - something like 240 grit if it's a heavy thick paint - then progress to 400/500 grit and finally finish at about 800 grit. Take it down so the paint is off and you see the original body colour underneath.

All a body shop will do is "key" the paint like this - they'll do it all over but just at 500-800 grit so the paint looks "dull", then either they'll do a "blow over" which is just base and lacquer straight on top of the keyed paint, or they'll put a primer/levelling/guide coat on first which they can similarly smooth at 800 grit, potentially giving them a better/smoother surface to put the top coats on.

So in prep, the body shop will take any rogue paint off - or at least flatten it down so it's smooth compared to the rest of the paint, then spray over it.

Don't use wire wool - it'll just scratch everything very badly. And Nitromors won't touch acrylic paint. Acrylic paint thinners will fetch the paint off, or pure acetone (Ebay). Pure Isopropanol is less vicious and might cut through the paint with rubbing but no guarantee. But I guess if the black paint is household paint (emulsion, matt or gloss) then you could use Nitromors on it safely and it won't attack the Rover paint on the bumper.

You could also use a cutting compound like T-cut, G38 or even toothpaste. It's a hell of a lot of effort if you use T-cut or toothpaste, but effectively you'll be able to abrade the paint - but much more slowly than using 240 grit abrasive paper.

If you wanted the rogue paint off and the body colour resotred, you'd probably sand most of the paint off at 500-800 grit and then choose a cutting compound and you might be able to remove all traces of it and have the bumper look like there was never any rogue paint there in the first place. Be extremely careful if you stray onto the original Rover paint though, as it's microns thick and a few rubs of cutting compound or even sand paper and you'll be through it anyway and white primer will be showing underneath.
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Hammond
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Re: Removing paint

#3 Post by Hammond » Thu Aug 15, 2019 4:57 pm

Sorry Johnny I meant I want to take off all original paint as some of its badly flaking anyway. I want to see how badly the bumper is underneath the messy paintwork. I appreciate it can be sprayed over but some of the grey plastic can already be seen so I thought I'd take it all off to see if the bumper is worth keeping or should I try and source one in a better condition.
Current:
416Si 'Ocean Blue' (R426 BFC)

Previous:
216GSi Auto 'Gold' (H397 HUD)
414Si 'Ocean Blue' (R478 AHJ)
414SEi 'Bermuda Blue' (V52 VFL)
214SEi 'Nightfire Red' (M755 SVR)
214i Sprint 'Flame Red' (M726 JOH)
416GTi Auto 'Diamond White' (J668 GRP)

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Re: Removing paint

#4 Post by Kriss707 » Thu Aug 15, 2019 7:30 pm

Don't use Nitromors, or similar, as it will eat the plastic aswell the paint. It's pretty aggressive stuff.

If you have an Orbital sander (DA) use that to key the paint till it's feathered & all the flaking has gone. Don't go too heavy as you may bobble the plastic surface.

If you don't have a DA it's good old elbow-grease to key the paint.

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Johnny 216GSi
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Re: Removing paint

#5 Post by Johnny 216GSi » Thu Aug 15, 2019 10:01 pm

Hammond wrote:
Thu Aug 15, 2019 4:57 pm
Sorry Johnny I meant I want to take off all original paint as some of its badly flaking anyway. I want to see how badly the bumper is underneath the messy paintwork. I appreciate it can be sprayed over but some of the grey plastic can already be seen so I thought I'd take it all off to see if the bumper is worth keeping or should I try and source one in a better condition.
I'd say use wet & dry abrasive paper then. But if you take it down to grey plastic, you or the body shop will need to prime over the top.

I've done some plastic centre caps myself, taking off all the original Rover paint - I was down to 180 grit (really coarse) and the plastic surface was scratchy - I wondered if I'd ruined them. I went for the Hycote series of primers - a thin watery clear "adhesion promotor" (2 coats) then a plastic primer, then a high-build normal primer on top - they rubbed down to be really smooth and of course the plastic was extremely well-keyed so the paint stuck.

Some people use an acid-etch primer onto plastic - and some swear by it as providing better adhesion. All I'm saying is - if you take the paint off, think what state you're leaving the plastic bumper surface in and what a body shop will have to deal with when they come to spray it. If you fetch it all off with too coarse an abrasive paper, they'll likely tell you you've ruined it. And if you choose 500-800 grit, it's going to take you several days or even weeks.
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Re: Removing paint

#6 Post by Hammond » Sat Aug 17, 2019 10:32 am

Johnny 216GSi wrote:
Thu Aug 15, 2019 10:01 pm
Hammond wrote:
Thu Aug 15, 2019 4:57 pm
Sorry Johnny I meant I want to take off all original paint as some of its badly flaking anyway. I want to see how badly the bumper is underneath the messy paintwork. I appreciate it can be sprayed over but some of the grey plastic can already be seen so I thought I'd take it all off to see if the bumper is worth keeping or should I try and source one in a better condition.
I'd say use wet & dry abrasive paper then. But if you take it down to grey plastic, you or the body shop will need to prime over the top.

I've done some plastic centre caps myself, taking off all the original Rover paint - I was down to 180 grit (really coarse) and the plastic surface was scratchy - I wondered if I'd ruined them. I went for the Hycote series of primers - a thin watery clear "adhesion promotor" (2 coats) then a plastic primer, then a high-build normal primer on top - they rubbed down to be really smooth and of course the plastic was extremely well-keyed so the paint stuck.

Some people use an acid-etch primer onto plastic - and some swear by it as providing better adhesion. All I'm saying is - if you take the paint off, think what state you're leaving the plastic bumper surface in and what a body shop will have to deal with when they come to spray it. If you fetch it all off with too coarse an abrasive paper, they'll likely tell you you've ruined it. And if you choose 500-800 grit, it's going to take you several days or even weeks.
So would you say leave all the damaged areas and let the bodyshop deal with it? There are patches where paint is totally missing and it's down the the grey plastic
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216GSi Auto 'Gold' (H397 HUD)
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214SEi 'Nightfire Red' (M755 SVR)
214i Sprint 'Flame Red' (M726 JOH)
416GTi Auto 'Diamond White' (J668 GRP)

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Re: Removing paint

#7 Post by Paul_1978_yorks » Sat Aug 17, 2019 12:14 pm

You need to change your signature Steve! :D
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Re: Removing paint

#8 Post by Johnny 216GSi » Sat Aug 17, 2019 1:15 pm

Hammond wrote:
Sat Aug 17, 2019 10:32 am
So would you say leave all the damaged areas and let the bodyshop deal with it? There are patches where paint is totally missing and it's down the the grey plastic
Most likely preferable. They have to deliver a painted bumper to you that looks the part, so they'll have to do what's necessary one way or the other. I'm not sure doing it yourself adds anything. Perhaps if you took all the paint off, prepped the surface and it was ready to go in terms of just a spray over with base + lacquer, then they might thank you for making their job a little easier and you might get the job for less money - but to paint a bumper properly using the Hycote system, I'd say it would take 2 cans of adhesion promoter, 2 cans of plastic primer and 2 cans of high-build primer. Then add the cost of a couple of packs of abrasive paper and you're at £60 materials plus several days of your labour, and no guarantee you're going to get a good surface at the end of it.

Just let the body shop do it.
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Hammond
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Re: Removing paint

#9 Post by Hammond » Sun Aug 18, 2019 10:45 pm

Paul_1978_yorks wrote:
Sat Aug 17, 2019 12:14 pm
You need to change your signature Steve! :D
Good point
Current:
416Si 'Ocean Blue' (R426 BFC)

Previous:
216GSi Auto 'Gold' (H397 HUD)
414Si 'Ocean Blue' (R478 AHJ)
414SEi 'Bermuda Blue' (V52 VFL)
214SEi 'Nightfire Red' (M755 SVR)
214i Sprint 'Flame Red' (M726 JOH)
416GTi Auto 'Diamond White' (J668 GRP)

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