# Damaged paint during polishing.



## Wookie78

Good evening to all. 
Have today managed to damage the paint on my car (BMW 640 black,) 
I am assuming it's strike through? - have never experienced that or what has occurred previously. 
I am not a pro but have previously experience of full correction on several cars previously and have been using my flex about 3 years without problem 
I will admit I h ave struggled with this paint as it seems to be hard as hell. 
I did however Decide to attempt to deal with the orange peel before the defects as it's awful! 
Opted for the velvet pads as they are less aggressive. 
After taking pdg readings the boot and the wing look like they have been resprayed as readings were both"over" whereas the rest of the car was generally between 110 and 180. 
So used the velvet pads on a rotary on both these panels only to start as they had plenty to play with. 
To be honest they didn't do a great deal to the peel but removed 95% of the defects. 
After this there were some rotary marks which after a test spot seem to be removed using my flex 3401 with LC hydrotech blue pad using poorboys SSR1 - speed of about 4.5-5. Boot was completed with no problems (have enclosed photo) 
Moved onto the front wing and after about 2-2.5 passes I noticed what is shown in the photos so I stopped. There was no heat in the panel or in the pad at this stage. 
It looked like polish that had been "baked on" and I thought it reduced when I tried to clay it to remove (not sure if this was wishful thinking on my part though. 
The photos with the tape on are before I tried to get it off and without tape is after. I'm still not sure if it's been reduced looking at it even now. 
Should mention the work with the velvet pads was with carpro fixer completed one weekend and the ssr work was another weekend. On both occasions car was washed, clayed and fully decon'd
Have also used more aggressive compound previously (megs 105) on the car without issue. 
I am still struggling to work out what I have done,how I have done it and how to avoid it again in the future. 
Feeling gutted at the moment and am thinking about giving this all up as has knocked my confidence with machine work as worried it could happen again. Only upside is that is was on my car and not a friend / family members. 
It's possibly a schoolboy error but followed previous advice and methods (pdg, test spot, less aggressive compound etc...). 
I'm hoping someone can offer advice on what I've done wrong on this occasion. 
I've kind of resigned myself that it's a respray now.

Thanks in advance for any assistance.





































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## Christian6984

It looks like the crease of the wing has caused it to me, if you plan on doing the rest of the car i would be taping off stuff like this as its where your most vulnerable that and edges of panels


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## wish wash

It does look like strike through. Paint is very thin on edges, that's why you need to be careful when doing edge work. Were you polishing it with a big 5-6 inch pad.


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## stangalang

So a couple of things, 

1) this is why I'm very specific with my terminology. A burn through and a strike through has become an interchangeable term, which causes a lot of confusion as they are both defects in their own right. What you have is multiple strike through, and has nothing to do with heat generation. You have simply removed more material than you had to play with 

2) taping edges isn't the answer, as many like to believe. Defects go upto and onto edges and as such, need polishing too. Learning to navigate panels is actually safer than learning to rely on other items to protect it. 

3) If I'm reading right, panels varied from 110 to 180um? Thats indicative of previous work (be it polishing or painting), for a machine painted panel to vary by essentially 33% it is giving you a clue (if that was indeed what you read it as


Honestly, I think there may have been multiple "school boy errors", wrong tool, wrong pad she, wrong pad choice, maybe wrong speeds, direction of polishing, focus of cut from the pad. No idea if you used a soft or hard backing plate and what pressure you applied etc. 

Im wanting to be honest and informative without coming across as negative. Its a teachable moment and the more information you have the better your next experiences will be. I truly think you need to grab some old panels, and intentionally damage them, so you learn how it happens, this will help you avoid it in the future. I recommend it to anyone learning machine polishing, they get to caught up in the what, and don't think about the why. If you can understand the why, then making decisions is easy


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## Wookie78

Thank you all for your replies (unable to thank on the forum as have less than 20 posts). 

The pad I was using was a 4" on the flex. It was the lake county smaller backing plate which is hard (Wasn't aware there is a soft one available?). 

Stangalang I appreciate your comments and straight talking and I haven't take them in a negative way so thank you.
Your suggestion of damaging a panel is a good idea that I haven't thought of previously. 

I was trying to identify the what to ascertain the why (if that makes sense). 
Have not had either burn through or strike through previously. 

I take on board all your points about multiple potential errors and am hoping to use this to educate myself (and hopefully others reading this) on how to identify this and avoid this situation. I appreciate the error was on my part but am unsure of how to go about identifying what the mistakes were. 

Your observation on paint depth in point 3 is correct and I had identified this, which is why I selected the the panels that have been resprayed and were reading "over" on the PDG - which I believe means are over 1250um (based on the range on the unit and the instructions). 
The wing is obviously a respray as in certain light you can see the colour difference to the rest of the car. 

I think maybe it was these readings and the fact that the paint appears to be very hard that may have led me into a false confidence in this respect. 

I will be watching all the videos online that I had previously and try to find some new ones and basically go back to the beginning and then attack some scrap panels. 

Any further advice from yourself and other members would be appreciated.


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## fatdazza

If reading was over 1250 um could it be that the panel has been filled for a previous repair and what the PDG was measuring was the filler plus the paint, leading you to believe there was much more paint than there actually was?


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## [email protected]

It's a bit of a steep learning curve I'm sorry that this has happened to you but at the end of the day what's happened has happened.

Just a couple of points for you. You cannot polish orange peel away it needs to be wet sanded. 

A rotary is not the tool of choice really as you can see now you can cut quickly and safely with a rupes and the megs microfibre system as it has a larger throw.

You should understand that there is less paint on the edges of a panel so you should be cautious. 

Gtechniq were doing detailing sessions earlier in the year I would encourage you to go to one if you could, as having a professional critique and teach you the correct technique is better than watching youtube or reading notes on here.


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## Wookie78

Thank you all again for the replies and advice. 

It's happened and like you say it's a learning curve - just wanted to educate myself (and others on here) by getting some more experienced observations and advice. It was the pdg reading that was throwing me and the fact that it was so high is why I was "testing" those panels rather than ones with lower readings. 
(Just to note - the damage was done using the flex 3401 not the rotary - that was only used on a test section to see if it would reduce the orange peel with the car pro pads.) 

Moving forward I will start from first principles again and have been looking for training courses online and will have a look at the Gtechniq one - thank you for the pointer. 

Will also be getting some scrap panels to play with and damage as per previous advice. 

Hoping it helps others on here avoid the mistake I have made. 

Thanks again.


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## stangalang

[email protected] said:


> It's a bit of a steep learning curve I'm sorry that this has happened to you but at the end of the day what's happened has happened.
> 
> Just a couple of points for you. You cannot polish orange peel away it needs to be wet sanded.
> 
> A rotary is not the tool of choice really as you can see now you can cut quickly and safely with a rupes and the megs microfibre system as it has a larger throw.
> 
> You should understand that there is less paint on the edges of a panel so you should be cautious.
> 
> Gtechniq were doing detailing sessions earlier in the year I would encourage you to go to one if you could, as having a professional critique and teach you the correct technique is better than watching youtube or reading notes on here.


You absolutely can reduce orange peel with a rotary and denim pads, even the 3401 if the paint allows. They are very effective when used properly. Total removal will absolutely need sanding yes


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## camerashy

If you want one to one training and are close to Saddleworth their is no one better than Matt (stangalang) as above both a perfectionist and good trainer


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## TenaciousTed

This is why I consider machine polishing to be the danger zone.
You probably haven't done anything especially stupid, it's just that there's a skill to machine work which requires quite a bit of learning and experience to attain.

There's a good chance if I had been let loose on that car I'd have done a lot worse, so don't be too hard on yourself.

This is one area where the pros do it best and us hobbyists can't just read a few guides and watch a few videos and obtain anything approaching the same kind of results.

I'll gladly do safe washes, hand polishing and waxing until the cows come home. But if I need machine polishing or proper paint correction, I'll be going to the pros.


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## jonjay

stangalang said:


> So a couple of things,
> 
> 1) this is why I'm very specific with my terminology. A burn through and a strike through has become an interchangeable term, which causes a lot of confusion as they are both defects in their own right. What you have is multiple strike through, and has nothing to do with heat generation. You have simply removed more material than you had to play with
> 
> 2) taping edges isn't the answer, as many like to believe. Defects go upto and onto edges and as such, need polishing too. Learning to navigate panels is actually safer than learning to rely on other items to protect it.
> 
> 3) If I'm reading right, panels varied from 110 to 180um? Thats indicative of previous work (be it polishing or painting), for a machine painted panel to vary by essentially 33% it is giving you a clue (if that was indeed what you read it as
> 
> Honestly, I think there may have been multiple "school boy errors", wrong tool, wrong pad she, wrong pad choice, maybe wrong speeds, direction of polishing, focus of cut from the pad. No idea if you used a soft or hard backing plate and what pressure you applied etc.
> 
> Im wanting to be honest and informative without coming across as negative. Its a teachable moment and the more information you have the better your next experiences will be. I truly think you need to grab some old panels, and intentionally damage them, so you learn how it happens, this will help you avoid it in the future. I recommend it to anyone learning machine polishing, they get to caught up in the what, and don't think about the why. If you can understand the why, then making decisions is easy


I agree with this assessment totally.

My first thought was that the backing of the pad and foam come lose and cause the machine backing plate to strike the paint. This is why its gone right through the clear, paint and to the primer.


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## jonjay

stangalang said:


> You absolutely can reduce orange peel with a rotary and denim pads, even the 3401 if the paint allows. They are very effective when used properly. Total removal will absolutely need sanding yes


Yes you can however i would warn the denim pads are quite hard to master and its just as easy to put damage into the paint that is incredibly difficult to remove than the orange peel itself.

Wetsanding is "easier" and quicker with the right tools, technique. I guess anything is with the right tools and technique


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## Mr Whippy

Oops.

One of the first things I learnt was wet sand is the only proper way to flatten lacquer... still with it’s risks but seemingly a lot harder to go wrong, vs the near infinite variability in a rotary/pads to do a similar job.

I’m sure some can machine it flat quickly and safely, but I can’t imagine that it’s more efficient on lacquer removed vs wet sanding?!


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