|The MGA With An Attitude
PAINT STRIPPING (not Striping) - PT-121
This is an often discussed subject, also often dusty, sticky, slimy, messy and/or smelly. How do you remove paint? Let me start with one of the slickest methods first.
On June 19, 2011, Steve Landry in Phoenix, AZ, USA wrote:
"A local body man was working on a car door. He took a single edge razor blade in a straight scraper and shaved the paint off as easy as you please, right down to the primer and about as fast as I can type this. Clean, enviro-friendly and cheap. Ron gets a whole box of blades and a stout scraper and it works like a charm. Did that door in about five minutes".
This technique will work well on convex surfaces with simple bends and gentle curves. Fortunately this includes virtually all of the exterior panels of an MGA, but not applicable to very much under the skin.
Another recommendation is to heat the paint until it melts and and blisters, or at least goes soft, and then scrape with a razor blade. In my younger years I removed multiple layers of paint from a whole house using a special purpose heated flat iron and a sharp edge putty knife. For coutoured surfaces the prefered heat source might be an industrial hot air gun (super hair dryer). This is likely to work well on thick gooey asphalt based undercoating.
The next technique is my own doing when in Spring of 1998 I stripped all of the paint from the outside shell of my MGA. In essence I power sanded the whole thing in one day, but like abrasive blasting, it requires different materials and different techniques for alloy or steel panels. For the nitty gritty details see Restoration RT_627.
This is the messiest chore of all, chemical stripping. You should start with plenty of fresh air ventilation and nitrile or Viton® or silicone "rubber" gloves. Also wear old clothes, as you may well end up with some holes in the cloth, and certainly lots of stains that will never wash out. You can use any kind of chemical paint stripper you like, and you will always come to the same conclusion. The chemicals are too darned slow. You can soak and soak and scrape and scrape, and it still takes forever for the chemicals to penetrate and soften the full thickness of the paint. If you run into any plastic body filler, all bets are off, go get the medium grit power sander. When finished you have to figure out how to rinse away or neutralize the chemicals before painting, and chemicals love to hide inside of spot welded joints (until it's time to blister your fresh paint). Manual chemical stripping may be suitable for a few small panels, but I wouldn't recommend going after the whole car body this way. Chemical stripping is much more appropriate for smaller parts with intricate shapes that cannot be scraped or sanded.
Redi Strip is a company name and commercial trade name, sometimes used generically when referring to commercial chemical stripping service. From about 1960 the company has been chemically stripping paint and bondo from car parts (and lots of other things). For a rusty steel car body they start with a bath in a vat of paint remover. After a good long soaking and a wire brush rinse to bare metal, it can go to a different chemical bath to remove rust. Not just turning red oxide to black oxide, but actually removing all rust down to bare steel. The shell will return with nothing but virgin steel, and of course pits and/or holes in place of any prior rust. It will be given a water soluble coating that may prevent rusting in covered storage for up to six months. Before painting it needs a bath in fresh water and a gentle brush down to remove the protective coating. The process has a few endearing features. First it is very effective and pain free. Second, it is likely to be relatively expensive, in light of current environmental protection regulations. And of course you have to transport the parts to and from the service company.
We tend to use this term in a generic fashion too, but there are many different kinds of blasting media. For removing heavy rust from structural parts like chassis frames, suspension parts and wheels, you can use abrasive blasting. This is commonly referred to as sand blasting, and in fact you can use sand, which can be almost dirt cheap, readily available and environmentally friendly (sort of). Just don't put it back in the kid's sandbox after use. For fast work on tough parts you can use "BLACK BEAUTY®". This is another registered trademark that is commonly use generically when referring to ground and sifted coal slag. The stuff is not only dirt cheap, but almost "pay you to haul it away" sort of waste material. Most of the purchase price is in the packaging and transportation and retail markup. Use with a big nozzle, lots of pressure and air flow to rip coarse scaly rust from structural steel parts. If you use this on sheet metal turn the pressure way back to avoid pitting the steel surface or warping panels. Never use it on soft brass or aluminum or pot metal parts.
Working your way down the list of blasting media from aggressive to mild mannered runs the gamut from silicon carbide, Black Beauty, aluminum oxide, white aluminum oxide, steel grit, steel shot, crushed glass (glass beads), walnut shells, ground corn cob, plastic beads (in wide variety), pumice, and soda blasting. The last one is almost always Bicarbonate that can be coarse and fairly aggressive to fine and gentle. Its primary hallmark is being environmentally friendly. "Bicarbonate of soda" is the stuff you might mix up and drink to settle an upset stomach (antacid). Baking soda goes into some food you may cook before eating. It also makes an excellent cleaner to neutralize acid on your car battery. The trick to any kind or abrasive blasting is knowing what you are doing before you start, so you get effective results without ruining the part you are trying to restore.
FREEZE AND CHIP
This is pretty much what it sounds like, and may be (maybe) effective for thick asphalt based undercoating. A few people have reported success by leaving a body tub outside to freeze in cold weather, then scrape and chip away the brittle frozen material. While it doesn't sound like much fun, it could be a lot easier than trying to scrape away the super stiff goop when it's warm.