Soda Blasting Body. Alternative to sanding?

[Bryan Boyle]

Richard got me thinking...and I was wondering what the current thinking is on soda (not bead, not sand, not walnut...) blasting to bring the car down for paint prep.

Not that I'm at that stage yet...mechanical stuff first...I know that there was some peripheral discussion of it on the old lotuseuropa yahoo group way back when...and progressive sanding seems to be the 'go-to' method (I did use a  fiberglass-safe stripper suggested to me by a marine fiberglass refinisher back when I did it, neutralized heavily, couple soap and water washes afterward; the only thing left was 320/400 finish sanding and it didn't seem to harm the plastic...and the paint job has lasted (from what I can see) since '08).

Just getting ahead of myself, but scribbling notes for when that awful day comes that I start to disassemble 3291R in prep for refinishing the coachwork.

Just angling for thoughts.  I know the results are dependent on the skill of the operator, but sodium bicarbonate is 1) fine grained and friable, 2) environmentally more friendly than chemicals, and 3) potentially less labor intensive at least to get back through the color layer to the underlying gel coat.

Just throwing this out there.
 

[Richard48Y]

My experience so far.
My only local source for blasting soda is HF at $50.00 per 50 Lb. bag. 
Some paints are almost too tough for economical Soda Blasting.
On the red car I found a razor blade in a handle to be the hot ticket to get down to primer.
Soda removes primer very well.
On my car the factory paint layer is really stubborn, it is taking too much Soda.
I am going to try a heat gun and razor first, then finish with soda.
Try to get a blast setup that includes an agitator, my cheap HF unit has me shaking it to prevent occasional clogging.
Good flow control of the air and soda is important to economy.
It really does not take a large volume of soda so much as high air velocity.

There are a lot of negative claims regards soda blasting but if you look at the dates most are a decade or more old.
It is VERY important to rinse the blasted parts with Holdtight before applying any finish.
I bought the five gallon bucket, it is used diluted, but I have 3.5 cars to do.
I did try a DA sander and did not like how it does not work the entire surface evenly.
Chemical stripper would be the least expensive in dollars and time so long as it will not contaminate the 'Glass.
I may resort to stripper if I cannot get the razor blade to work.

[Bryan Boyle]

My experience so far.
My only local source for blasting soda is HF at $50.00 per 50 Lb. bag. 
Some paints are almost too tough for economical Soda Blasting.
On the red car I found a razor blade in a handle to be the hot ticket to get down to primer.
Soda removes primer very well.
On my car the factory paint layer is really stubborn, it is taking too much Soda.
I am going to try a heat gun and razor first, then finish with soda.
Try to get a blast setup that includes an agitator, my cheap HF unit has me shaking it to prevent occasional clogging.
Good flow control of the air and soda is important to economy.
It really does not take a large volume of soda so much as high air velocity.

There are a lot of negative claims regards soda blasting but if you look at the dates most are a decade or more old.
It is VERY important to rinse the blasted parts with Holdtight before applying any finish.
I bought the five gallon bucket, it is used diluted, but I have 3.5 cars to do.
I did try a DA sander and did not like how it does not work the entire surface evenly.
Chemical stripper would be the least expensive in dollars and time so long as it will not contaminate the 'Glass.
I may resort to stripper if I cannot get the razor blade to work.

I'm dealing with the original lacquer (its heavy cracking is an indication it's probably NOT an enamel); I'd be worried about gouging the glass with the razor, though. 

I've read about the remnants of soda blasting needing a good washing off before starting the prep/prime/paint.

(FWIW, I know the old listers were either holding their breath or hoping 693R ended up as a mass of fiberglass goo on the garage floor so they could say "I told you so", but using the marine fiberglass friendly stripper back in '08 really did not cause any issues, migrate into cracks to blow out later, or give my body guy any aggida (he was more careful about keeping silicones out of the shop) and said it left him a good palate to start from after he finished getting the remnant of what I didn't pull off for him to start his attention to the prime/paint process.

Like I said, this is far down the road right now, but it's good to have a plan, albeit strategic at this point.

[dakazman]

  I have found the easiest way to get rid of the paint is wet sand with 80 grit. once you hit primer, go to 120.
   i haven't seen your finish but the razor blade cupped in a slight bend, dragged across the paint is also very good. you can also use a kitchen knife bent as a cup. see ancient Japanese boat building tools. don't laugh they work.
dakazman 

[My S1]

Brian,

I had a Monza Junior go kart body media blasted with soda.  As you mentioned it is highly dependent on the operator.  In most areas it went well however he did dig a bit too deeply in other areas.  It was difficult to find a shop that uses soda, most like to have only one booth for only one media.  I waited around for him to do the job and it went quickly.  If you have the equipment and the venue I would say do it yourself.

[Clifton]

I did the razor blade too. About a 1/4" strip at a time. It came off surprisingly fast. If your angle is right, it won't gouge.

[Richard48Y]

At the end of the day the answer is "All of the above".
Soda blaster was not being effective on the second layer of paint.
Heat gun was no help on the silver layer of paint either, it may have been Imron.
But stripper did soften it enough for the razor blade to be fairly effective, at three layers.
That got me down to a primer which the soda blaster removed fairly well.
So I am finally down to original paint and repair sins.
Not certain this lid is worth continuing with and I already have the cost of a new one into it. (Sans shipping)

[Richard48Y]

Called Klean Strip, they recommend GAR2000.
Available at O'Reilly Auto Parts.

Klean-Strip Aircraft 1 Gallon Paint Remover - GAR2000
Part # GAR2000 Line: KLN

Of course this replaces the old formula the EPA banned, still works but is slower.
It is recommended to cover it with plastic while it works, about fifteen minutes.

I will try this as I cannot bear the expense of doing the entire body by soda blast alone.
Once the majority of paint has been removed I expect to finish by soda blast as it gets to all the nooks and crannies.

[Richard48Y]

Been working with the stripper.
Takes about three applications to remove nearly all of whatever the Bahama Yellow paint was.
Do not think it was Lacquer.
From this point the soda blast should work quickly.
This is now my plan for the entire car.
Stripper may be somewhat difficult to use in tight areas such as the forward door pocket.

[Sparkrite]

Very useful thread as I also intend to strip and re paint my car in the future,and I can foresee the stripping as being alot of work.
 One question I have is how do you deal with the inevitable areas of bare fibreglass for refinishing once all the stripping has been done. Do you paint on a gelcoat(which leaves a tacky surface) or a flow coat which contains wax?

[dakazman]

 

Very useful thread as I also intend to strip and re paint my car in the future,and I can foresee the stripping as being alot of work.
 One question I have is how do you deal with the inevitable areas of bare fibreglass for refinishing once all the stripping has been done. Do you paint on a gelcoat(which leaves a tacky surface) or a flow coat which contains wax?

    I would do neither, until recently I would just use a good 2k primer, however now I’m testing the composite veils to mask the fibers that have been damaged due to hairline cracks and weathering.
Then prime .
  Just my 2cents
Dakazman

[EuropaTC]

One question I have is how do you deal with the inevitable areas of bare fibreglass for refinishing once all the stripping has been done. Do you paint on a gelcoat(which leaves a tacky surface) or a flow coat which contains wax?

If the surface is hard and showing a resin rich gel coat layer then I leave it alone. If there's signs of damage, either from paint stripper or using a sharp tool such as a chisel/blade then I'll gently grind away to the matting beneath then paint on resin and refinish with surface tissue(veil). I never use commercial body filler, only resin, a lot of tissue and making sure it's fully wetted out. Then leave it to harden for as long as you feel able to providing you're in dry conditions. I'm sure I read somewhere that Miles Wilkins left his repairs for 4-6weeks before doing anything but generally I've been a week, maybe more as I work around the car.

Once hard I'll use 80grit production paper (used dry) on a sanding block to blend it in.  I'll use polyester spray filler (Upol or similar) to cover the entire surface as it easily fills 80grit scratches, in fact I use it over the whole car.  Dry sand that, usually 240grit, and then put on conventional primer, the first coat one colour with the rest a different shade. Dry/wet sand that back with 400/600 and don't break through the first primer layer.

After that you should have repairs that won't sink or show through the paint a year later.

Brian

[Richard48Y]

After three applications of stripper the rear deck is to the point it may be easily finished with the soda blaster.
This was a very tough paint, pretty sure it was an enamel.

[kram350kram]

Add methylene chloride to your stripper. Standard strippers used to have it until the EPA got involved. I add 10 % by volume to the junk you can get now and it strips as it should.

[Richard48Y]

One more experiment to try.
I have a small bag of Walnut Shell blasting media.
Going to see if it will remove the remnants from the engine cover.