Thursday, January 9, 2014

Stripping the Rear Quarters and a Lesson to Share

Steady progress has been the order of the realm this past few weeks and I am quite happy with the ground that has been covered.  With a few new parts and tools added to the inventory, I had reached a point where it was time to get the rear quarter panels stripped of all remaining original paint to see what measures would be required to get them into a clean, rust-free bare metal state that would allow proper bodywork to proceed. 

Of the options available to remove paint from exterior surfaces of the body, I prefer chemical stripping over all other methods most of the time.  Chemical paint stripper is very easy to control, does an excellent job, and does not damage or alter the surface of the parent metal at all.  By using a razor blade scraper to skim the softened paint from the metal, the job of stripping an entire panel goes surprisingly quickly even with the “wait time” involved in letting the stripping chemical do its job.
After a short ceremony to pay homage to the last vestiges of medium metallic blue color that remained on the car, I applied the first coat of stripper using proper chemical resistant gloves, respirator and eye protection.  Allowing about 20 minutes for the surface coat to completely lift from the surface, I scraped the top layer of paint easily away from the surface with the razor scraper.  Generally speaking, this would leave the primer layer(s) on the surface that would simply require a second coat of stripper to remove completely.

Once all of the original paint and primer was completely removed, I rinsed the panels clean with distilled water on a shop towel to remove any stripper residue and neutralize the stripper.  The result was nice, bare metal panels that were ready for a close inspection and evaluation in order to begin planning the repair and prep work required to plan for primer and the sequence of conventional bodywork to come. 
The panel evaluation work is best accomplished without any sort of prep coatings or etchants on the panel so that even small details are not lost or masked.  This is particularly important on 40+ year old muscle cars as many manufacturers had not yet adopted immersion priming methods or anti-corrosion primers on all surfaces of the body.  EDP primers were still decades away before the last genuine muscle car rolled off the assembly line.  A close inspection is often remarkably enlightening as was the case here.  In fact, what I realized based on my inspection was I had a very unique opportunity to educate on the hidden evils that can exist under “survivor” original paint or older restoration work.  As such, the next section will cover this critical information with some very graphic examples of “what lies beneath” in more cases than you might imagine.
Aircraft stripper is a favorite of mine to chemically strip the last bit of factory paint from the rear quarters.  One thing to notice here is how relatively "rust free" the left rear quarter appears before the stripping work begins.

The first coat of chemical stripper very quickly starts to lift the original finish and is very easy to manage as evidenced by the lack of runoff of the stripper to the side of the quarter.

Nitrile gloves and an inexpensive razor scraper are an excellent combination for removing loosened layers of paint quickly and easily with relatively little mess.  I use a grout mixing tub to catch the debris for ease of clean up and to avoid crapping up my shop floor.

A bit closer look at the large curls of paint that are removed with the razor scraper.  Also note the remaining layer(s) of primer that will require a second coat of chemical stripper to remove.  Believe it or not, there is red oxide primer under the grey coating.

The top of the rear quarter has had its first round of chemical stripping complete and you can start seeing evidence of more extensive rust being exposed.  We will detail this discovery more in the second half of this article.

Moving to the front half of the quarter, the stripping process is identical and equally efficient.  A quick few minutes with the scraper and the second coat is applied over the same area and left to work for another 20 minute soak period.

After scraping off the second coat of stripper, the front half of the quarter is clean and down to bare metal.  Again, we see more evidence of the extent of surface rust that existed under the original paint and primer.

With all of the original paint and primer removed, the left rear quarter is completely exposed for a close inspection.

Moving to the right side quarter, the same stripping operation is applied.  In this shot, both the top and front half of the quarter has been completely stripped.

Here is an interesting detail that was revealed after the original paint and primer was stripped from the right rear quarter.  In the center of the picture, you can see where some sort of light sanding was done above the wheel arch at the factory before the car was painted.  It is not obvious what sort of flaw was being repaired, but 44 years ago, somebody thought it was important.
What You See Ain’t Always What You Get!

Nowadays, there is a tremendous amount of hype thrown around about preserving “original paint” as much as possible and avoiding stripping a car to bare metal during a restoration.  Well………bullshit.
Quite simply, with original paint left ANYWHERE on a body during restoration, you simply don’t what you don’t know because you can’t see what can’t be seen.  As it turns out, the rear quarters on the Boss were a perfect example in the most exemplary way.  If you look at the pictures below, you will see there are hints of what most describe as “minor surface rust” starting to peek out from the very weathered original paint.
As each layer of paint and primer starts to come off the panel during the stripping process, more and more evidence of surface rust starts to become exposed.  In fact, until the last trace of the base primer layer is completely gone, the full extent of the rust propagation is hard to imagine.  In fact, a general rule of thumb is that for every spec of rust you see perforating the surface of “original” paint, the extent of rust repair requirement is roughly 10-15 times larger in scale.  In other words, if you see a ¼” rust spot on the surface, the expected repair area will be approximately 2.5 to 3.75” across and often this can be a conservative estimate.
This simple fact is shown in undeniable and explicit detail in the following photographs of the tentacles of rust spreading widely across the panel that were completely hidden beneath the original finish.  Only until the panels were stripped to bare metal was the true extent of damage revealed.  Without this revelation, there is no way a proper assessment of the requisite repairs can be completed and any hope of a successful restoration of these surfaces is simply impossible.
With that, the lesson is to strip absolutely EVERYTHING to bare metal during a restoration to make absolutely sure the hundreds of hours of labor and untold thousands of dollars of investment you will make will be spent with maximum effect and long-term return.  It really is that important.
In the next update, I will document how to deal with the “ugliness” we have discovered.  Also, I will describe a simple process to reliably detect almost microscopic rust and how to eliminate it permanently.  Also, we will start getting into the repair of some small and moderate sized dents and dings.  Until the next update!
During the paint stripping process, the true extent of the surface rust propagation began to reveal itself.  In this close-up of the top of the left rear quarter, you can just start to see how the rust has extensive "tentacles" that extend far beyond the small spec that was revealed at the top of the painted surface.

A bit further rearward on the left quarter and this "rash" of rust became more and more visible as each layer of paint and primer were removed.  If you look closely, you will see a fair amount of primer is still left in the rusted area.

This is getting pretty ugly now.  After removing only the top layer of factory paint, the surface rust has been exposed and the true extent of coverage is pretty amazing.  Very quickly, it becomes obvious that the area that was originally visible is magnified many times over once we get all of the original paint and primer off the surfaces.
Pure ugliness.  Careful compare the detail in this photo to the one immediately above.  The speckles of rust here and there that were visible when we started have been revealed to be an extensive matrix of rust that extended all over the surface.  Roughly 75-80% of this rust was absolutely invisible on examination of the original paint!  Had I tried to preserve this finish in any way, the results in just a few years' time would be a total devastation of a very expensive paint job and likely the loss of the original panel.
With the top surfaces of the quarter stripped bare, you can clearly see why it is critical to avoid getting caught up in trying to save original paint in a full restoration.  What you can't see can definitely hurt you!


  1. Excellent documentation as usual Sven. It really is awesome to see some of the previous beliefs debunked with clear and incontrovertible evidence as you have presented here. I must say though that whilst it does not look pretty the fact it is "only that bad" after 40 plus years is a credit to what they could do at the time.

    1. Hello Mike and thank you. It is pretty amazing that the extent of the damage was not much worse considering how long my car spent in a coastal environment in less-than-ideal storage conditions. Lucky to be sure!

  2. Excellent expose' on the secret world of rust Sven! It's interesting (to me) how the rust under the paint is a kind of spiderweb pattern like it's either following trails of grain of the metal or crazing cracks in the paint itself. Great points on why to strip to bare metal and once again, you sway me toward chemical stripper over media blasting. Nice work.

    1. Thanks Alex! I couldn't help but feel a bit compelled to share this in light of recent trends in the hobby leaning in the totally wrong direction (in my opinion anyway). I'll probably get shot in the end.....

  3. I have never thought the whole 'save the paint and patina because it's cool' was a good idea. I can certainly guarantee that my car will have everything stripped before the paint goes on, and it is for this very reason. Thanks for the exposé Sven!

    1. Godd on you Grant. There is no good that can come of covering up this kind of thing and I am definitely NOT on the "patina" train like so many seem to be lately. You are doing it right on your car! Keep at it and thanks for the compliment!

  4. Nice description on stripping and a great argument for removing all the old paint. I found bondo on a fender that looked "OK". And rust does have a way of expanding, doesn't it? Those quarters are still nice looking. I'll be looking forward to your next step and what other hidden rust you find. Hopefully, it's nothing serious.

    1. Thanks Dennis! I am really getting frustrated with some of the "trends" being touted by some very "big name" builders that will lead to nothing good for the preservation of the cars. As you know, rust never sleeps and any attempt to shortcut the proper removal of it will eventually come back to haunt.

      Fortunately, the rest of the quarters are actually very good, so what I showed above is the worst of it fortunately. I really owe the blog another update as I am a good bit farther along. Soon!

  5. Another episode of 'In the Garage with Sven'. Nice description. I'm a chemical stripper fan as well. I learned the lesson the hard way. On my first Mustang restoration, a 67 fastback, I warped the driver's side inner panel while sand blasting. I still cringe when I see it :(


  6. Thanks RJ. Blasting and chemical stripping certainly both have their place, but as you point out, they both have their concerns as well. I try not to spend too much time on the "beauty" surfaces with a blaster for the exact reason you have shared. It can sure make a mess of things before you know it!