Strip or media blast - pros/cons

al lkosmal · 08-11-2007, 12:54 PM

My 71E is gutted and ready for paint prep. I have had a local paint guru out to look the car over, quote, etc. He is recommending media blasting. Another local Porsche guy is recommending stripping. This car is so straight and rust free that I'm not sure that I want anything more than the exterior, battery boxes and front of the trunk blasted (light surface rust). It appears that this car had an engine fire at 88K and was garaged in Arizona since. It was originally silver and was painted black. I'm returning it to the original silver.

Anyway, why choose one method over the other?

Regards,

al

Augustus · 08-11-2007, 01:31 PM

I often thought about this too.

Last year I chatted with a fellow who does high end paint and body work.
I asked him what was the best way to remove paint from a car. He said, "media blasting"
Apparently a new media was developed just for stripping paint from cars without distorting the metal. As you might know, sand will distort the metal. People have used plastic balls and crushed walnut shells as a media in the past. He did tell me what was in the new media but I have forgotten.

After he media blasts, the body is blown with air and cleaned and then primed right away. And it is now that he sees the problem areas and goes to work repairing rust or dents.

Hope this helps.

gestalt1 · 08-11-2007, 03:21 PM

i had my 73 media blasted. if i had to do it over i would use peel-away stripper on any part of the tub that has undercoating then get it media blasted. the media blasting does not get the undercoating off. i would do the whole shell, why not? also make sure you drop off all the suspension and various painted brackets at the media blaster. it will save money and time to have them do everything.
-matt

Zeke · 08-11-2007, 03:32 PM

Stripping a car is a subjective decision. You might consider the condition of the existing paint. One respray sanded down thoroughly may be the way to go. If there is rust under the paint, or there is some bad body work you'd like to straighten out, then by all means, remove the paint in the local area(s). If the whole job is too thick or cracking, then you will be better served by either stripping or blasting. Obviously, the labor involved in hand stripping a car is what brings people to the blasting technique.

One of the best jobs I have seen was hand stripped and then touched up in the nooks and crannies by blasting. They were able to do 95% of the work quickly enough and the last 5% took no time at all. There was still the medium everywhere to clean out, which can take some time. Every car I have seen that was blasted leaked medium out for sometime, even after thorough cleaning and the project was finished and being driven. You find it on the carpets, under them and on the suspension, etc. Of course, I would prefer plastic to sand if it was going to land on my axles, shift linkage and other critical parts.

The "new" media are plastic or soda.

TimT · 08-11-2007, 03:52 PM

Quote:

sand will distort the metal

Only true if performed by unskilled blasters. Sand can distort the metal. Its not the sand, but poor blasting techniques that will warp large panels.

The most thorough method would be to dip the tub.. It removes everything.. to the extreme... Those cardboard "mufflers" that are in the longitudinal members will disintegrate.. If you want to retain heat dipping isn't the way to go.. unless you will open longs and replace or reconnect the heating ducts

Id go with media blasting if this is to be a street car (media includes sand, in the hands of a good operator)

For a track car.. dipit.. dip it good ....

some pics of a project in the shop now

Striped tub ready for a trip to the tank for a nice bath

Tub back after its bath...hasn't been this clean since it got onto the assembly line

trconway · 08-11-2007, 05:06 PM

TimT where did you have this done? I'm in NJ and looking for a place.

TimT · 08-11-2007, 05:14 PM

Redi-Strip; Allentown, Pa. (610) 437-7878

Green 912 · 08-11-2007, 05:33 PM

I used them as well but they cooked the tub at 700 deg first then washed the ash off with an acid dip and water wash off. Dipping is a solvent based method that can cause issues when the rockers and other trapped spaces keep goo in them. This is a 77 that is going to be a FG 73 rsr look track car.

As was said this method gets everything right to metal.

ChrisBennet · ChrisBennet's Garage

My friend Palmer power washes the paint off. Course his "power washer" will cut steel and concrete. When he's not using his machine on cars he descales ships with it. Maybe there is some place like that on the west coast?
-Chris

Brother · 08-11-2007, 07:57 PM

What's a ball park estimate for each of these methods?

Mo_Gearhead · 08-12-2007, 04:40 AM

QUOTE: "What's a ball park estimate for each of these methods?"
_____________

I'm sure it will depend on area of the country. Here, they did the entire car
(tub, fenders, doors, etc. ) for $400 ...that was however, 5 years ago (inflation?).

They used crushed walnut hulls. As someone stated, it DOES NOT remove the undercoating.

Formerly Steve Wilkinson · 08-12-2007, 05:27 AM

Is there a danger that the blasting will remove the galvanizing? Of course that's not a consideration for a racecar. I've also heard that it's a moot question because galvanizing only last for something like 25 years at best anyway...

Zeke · 08-12-2007, 06:33 PM

Quote:

Originally Posted by Formerly Steve Wilkinson

Is there a danger that the blasting will remove the galvanizing? Of course that's not a consideration for a racecar. I've also heard that it's a moot question because galvanizing only last for something like 25 years at best anyway...

Well, I just spent the better part of two days prepping and welding on an '84. Now that's only 23 years old, but I'm afraid I'm going to have to conclude that the stuff has got more than 25 years in it.

cerberus1 · 08-13-2007, 05:46 AM

Gestalt:

What is "peel-away stripper" and does it really work (better than heat and a scraper)? I'm looking for the best (read easiest) method for removing undercoating. Yep, I've read the threads. Just wondering if "peel-away" is something new.

al lkosmal · 08-13-2007, 06:41 AM

Augustus,
Media blasting is what the local paint guru recommends too.

al

Ray_G · Ray_G's Garage

I guess I will toss in my .02 cents here as well. I guess it depends on what you want, and what condition of the current paint is. I just stripped my 76, I did not do the underside, or trunk. but I did sand blast the seal channels and I had to get coarse grit sand paper on a grinder and sand the hell out of the car because a lot of the paint had peeled leaving bare (galvanized metal) Rust still formed and I probably took off most of the exterior galvanizing. Once I got all the surface rust removed I acid etched and then used a zinc/self etching two part epoxy primer. On the other hand if I was going to do a complete restoration on a car without much rust I would media blast. Just a paint job with decent paint no rust on the body I would chemically strip. Just depends on what you are dealing with. Whatever gets the job done properly with the least amount of work.

Zeke · 08-13-2007, 08:45 AM

Quote:

Originally Posted by Ray_G

I guess I will toss in my .02 cents here as well. I guess it depends on what you want, and what condition of the current paint is. I just stripped my 76, I did not do the underside, or trunk. but I did sand blast the seal channels and I had to get coarse grit sand paper on a grinder and sand the hell out of the car because a lot of the paint had peeled leaving bare (galvanized metal) Rust still formed and I probably took off most of the exterior galvanizing. Once I got all the surface rust removed I acid etched and then used a zinc/self etching two part epoxy primer. On the other hand if I was going to do a complete restoration on a car without much rust I would media blast. Just a paint job with decent paint no rust on the body I would chemically strip. Just depends on what you are dealing with. Whatever gets the job done properly with the least amount of work.

There's such a thing as 2-part epoxy that is also self etching? I thought it was one or the other. What brand can I buy that does both things? Epoxy alone is rather expensive (not that we don't want the best). What does the dual purpose stuff cost?

gestalt1 · 08-13-2007, 09:32 AM

here is the web site for peel-away. http://www.dumondchemicals.com/html/products.htm
the key difference with this stuff is that it uses plastic sheeting to stick on the stripper after it is applied to the body. the sheeting keeps the stripper from evaporating so it can keep working on removing the undercoating. it also seems to be easy to handle and environmentally safe. i does work. the problem with strippers is getting the cruddy residu off the car and getting a clean surface. thats why using media blasting after the stripper makes sence. the media blasitng leaves a great surface with a lot of tooth for primer to hold on to.
-matt