Wednesday, December 29, 2010

Some simple but effective restoration tips by request

Since starting this blog, I have received numerous private messages inquiring on various techniques I use that I may not have detailed appropriately.  The two that seem to come up most often are: 
A. Undercoating removal
I had a rather funny but serious inquiry from a buddy asking why I never seem to complain about undercoating removal like so many other restorers.  At that point I realized I never covered that phase of my work because I just don’t struggle with it as a result of some sage advice from a fellow hobbyist and Studebaker restorer friend who was kind enough to recommend the undercoating removal procedure I use.  However, before I get to the details, I am going to warn you that what I am about to describe kinda runs against logic when you see the tools involved, but trust me, the process works and works very well (it’s super quick too!).
Quite simply, the way I remove the old crusty undercoating from any area is with a pneumatic air hammer.  Now, before you fall off your chair laughing at the thought of using an air hammer on your delicate sheet metal, take a second to follow along.
The two critical things in making this whole idea work is a good, quality air hammer that has an on board air adjustment and LOW air pressure.  I use a nice Craftsman adjustable air hammer that came in an air tool set I got several years ago (see photos).  With the air pressure dialed to no more than 20psi, and a slightly dull, broad blade chisel, the old undercoating practically jumps off the metal in fine pieces, leaving a very clean surface that can easily be cleaned up with a bit of solvent.
The technique is to lay the chisel edge at a relatively shallow angle to the surface and let the low pressure hammer blows “shock” the undercoating off the surface.  You can use your hand to direct the chisel head to help in removing undercoating from quite intricate areas.  With just a little practice, you can strip an entire wheel well in about 15 minutes.  My front fender aprons were heavily coated in undercoating when I started my resto.  Using this little trick, I managed to strip each side in less than a half hour each!  What little residue was left was easily removed during the sand blasting process in preparation for panel replacement (see earlier blog installments).
B. Chemical paint/goo stripping
I am a firm believer in using just about any means at your disposal to remove paint and other goo from your car during a restoration.  Also, while I like sand blasting for almost all rust and paint removal around the car, I do NOT like sending a car to a media blaster to remove paint/rust from the external body surfaces.  I’ll take care of that myself, thank-you.  I have seen far too many issues with the media and pressures used by most media blasters on the “beauty” surfaces of cars that I much prefer using my small, low pressure sand blaster to condition these surfaces AFTER using a D.A. sander and chemical paint stripper to do the bulk of the work head of time.
I am a big fan of products and tools that do more than one thing well.  I consider such things as nifty little bonuses and love when something works really well.  One product I really like for its multi-use features is a chemical paint stripper available at your local Home Depot (and other locations that carry the “Klean-Strip” brand of products, and it’s called Klean-Strip Premium Sprayable Stripper and is effective on paint, epoxy and polyurethane as well as powder coating, undercoating residue and seam sealer.  This stripper is better than any of the “aircraft” strippers I have ever used and is cheaper to boot. 
A word of caution is in order:  This is some of the nastiest poop you can get over the counter and will jack you right up if treated carelessly.  It will blister skin almost on contact and it stinks like death in a can, but work it certainly does.  Consider yourself appropriately warned and READ THE BLOODY INSTRUCTIONS AND PRECAUTIONARY MEASURES!
Aside from being a fantastic paint stripper, one of my favorite “bonus features” of this product is its ability to strip seam sealer and undercoating residue from just about anywhere.  As many of you will attest, old, dried seam sealer can be just as hateful (and often even more so) to remove than old undercoating.  This stripper will penetrate even the toughest seam sealer and lift it cleanly off with just a little scraping.  The accompanying photos will show how I used this stripper to remove the bulk of the paint, undercoating residue, spray adhesive residue and seam sealer from the cowl boxes on my Boss.
Another very important feature of this product is that it is neutralized and rinsed with odorless mineral spirits and NOT water.  Why on earth would you use water as a rinse agent on a restoration project where bare metal surfaces are regularly created?  With rust an ever-present enemy, any effort to avoid a moisture infusion is a worthwhile exercise.
I hope you find these two small tips useful in your restoration work.  As I come across other useful tidbits, I will try to document them here.  If you have any requests for information that I may not have covered appropriately, please feel free to drop me a note and I will do my best to document the information here.
Next time, I will cover more of my cowl panel replacement efforts!
Here is my favorite Craftsman adjustable air hammer that I use when removing stubborn undercoating.

And important feature is the adjustment knob in the handle of the air hammer.  This allows quick regulation of the impact force.

The trick is to use low air pressure to the air hammer.  Never go above 20psi when using this technique to remove undercoating.  If an adjustable air hammer is not available, adjusting the air pressure at the regulator works as well.

By keeping the chisel at a shallow angle to the surface, you run little risk of damaging the metal surface.  Also, note the wide, slightly dull chisel blade.

If you look closely at the trailing edge of the chisel, the undercoating is cleanly removed.

Another shot of the cleaned strip that results from just a few seconds with the air hammer.  At the low pressure used with this technique, the chisel is very easy to control and can even be "steered" by hand into very intricate places.

Here's a look at the same area after about 2 minutes work.  The residue that remains is very easy to remove with solvent or chemical paint stripper.

Here's a look at the undercoating on the drivers side cowl saddle area.

Another look at the drivers side cowl saddle area at the corner of the firewall.

After about 5 minutes work with the air hammer, the undercoating is gone.

A light residue is all that remains of the old undercoating and cleans up easily.

Here is a look at the outboard side of the passengers side cowl box.  The clean  bare metal is just as it appears after removing the undercoating with the air hammer.  No additional cleaning has been done here in an effort to show how cleanly some of the coatings come off the surface.

As chemical strippers go, it doesn't get any better than Klean-Strip Premium Sprayable Stripper.
Here, I have coated the entire inside cowl box with stripper.  Of particular interest is the inside corner of this panel which is completely sealed with old seam sealer.  No amount of scraping would make a dent in this stuff.

You can see the old undercoating residue that was left over is liquefied along with the old paint.

On the inside surfaces, the stripper tackles everything at once:  paint, undercoating residue, adhesive residue and seam sealer.

After two treatments of stripper, the seam sealer is gone along with the primer and paint.

Here is a look at the drivers side cowl box as well.

Here is a look at the undercoated areas that we previously stripped using the air hammer.  Note the clean bare metal that remains after the paint stripper was used to remove the undercoating residue.  I think we can work with that!


  1. Great Tips! I just wish you would have written this before I had done my hood and fender extensions. The stripper I chose... well.. sucks arse!

  2. Sorry about that Alex! I am really bad about skipping over simple things like this that I have taken for granted. Never figured any of this would ever be useful to anyone else.......until I started blogging about it that is.