Lotus Europa Community
Lotus Europa Forums => Garage => Topic started by: Bryan Boyle on Monday,April 24, 2023, 08:10:02 AM
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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.
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My experience so far.
My only local source for blasting soda is HF at $50.00 per 50 Lb. bag. :o
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.
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My experience so far.
My only local source for blasting soda is HF at $50.00 per 50 Lb. bag. :o
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.
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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
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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.
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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.
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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)
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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.
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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.
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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?
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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
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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
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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.
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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.
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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.
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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.
Yep, methylene chloride is one heck of a paint stripper. So good that it got banned..... ;)
In the UK we used to have methylene chloride thixotropic strippers and they were absolutely excellent in getting anything off, unfortunately that also included the gel coat if you weren't careful. For that reason they weren't advised for GRP bodies but I still used them up to a point. If you're stripping a car with multiple re-paints (my Marcos had 9 (yes, NINE) different coats of paint on it the first time I did it) then it's reasonably safe to use it to get rid of the outer layers.
I'd certainly use methylene chloride if I could get it but with caution. I'd never apply and leave it because the rate of attack on bare gel coat will upset you, been there, done that. The strippers I used to get would wrinkle the top couple of layers within 15-20 minutes and at that point I'd start scraping.
Incidentally, it will also attack you if you're not careful and it smarts a bit. Gloves, arm and eye protection are essential.
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Walnut shell blasting experiment done.
For this experiment I was mostly removing the thin paint/primer film patches left behind after chemical stripper.
Cost at HF, $30.00 for a 25 Lb. box.
Can be used from an inexpensive standard sand blast rig.
Consumption rate is high.
No Baking Soda odor but you may need to sweep or vacuum as it will not dissolve in water or the next rain.
Does not appear to etch Gel-Coat but does leave a coarser finish on remaining Bondo® and old repairs.
If you really want to avoid Soda Blasting and are not going through several layers of paint Walnut Shell media should work.
For cost savings I would use it as a final finisher after chemical stripping but that may just be me.
I think it is a little slower, and certainly more expensive per pound.
The "Good" stripper is $82.00 -$109.00 per gallon depending on purchase location.
Next experiment will be a final light coat of chemical stripper followed by coarse steel wool and water rinse.
I hope this removes the final remnants of old paint without having to run the big air compressor or deal with media blast residue.
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Was talking with a local shop which specializes in marine fiberglass repair/renovation here in the southeast MA area...while busy (obviously...getting the yachts and cabin boats ready at the marinas around here...has no openings until July), he is willing to take a look at what it would take if he's in the area. He mentions that after soda blasting, it's important to neutralize, with vinegar, the remnants of the soda that remain on the surface (which makes sense...sodium bicarbonate is highly basic, and vinegar acidic...so one would cancel out the other (with a little foaming) followed by a strong soap and water rinse, then let the surface thoroughly air dry in the sun.
Also mentioned that he's had good luck with micro glass beads (not the type that are usually used in blast cabinets, but down at the micron level...) and turning the pressure way down on stubborn top coats such as urethanes and catalyzed enamels. One of the caveats is that any glass that remains in the car has to be covered with aluminum foil, then two layers of masking paper (shiny side out), and any trim masked with duck tape (not paper painter tape) and ALL chrome removed, since the micro glass bead WILL etch the windows. And, it can leave a slightly 'toothed' surface, which would probably require a high-build primer to properly smooth before standard primer, sealer, and top coat.
I mentioned that the body thickness is NOT the 1/2" or more that a boat hull is constructed from; it's a polyester resin chopped strand slurry shot-gunned into a female mold, not hand-laid epoxy or injection-molded (IIRC, some builders licensed Lotus' VARI system to build their hulls...I may be wrong), so that has to be taken into account.
Figure, if he stops by the house (the soda method is environmentally friendly....wash down the drive with water), he's willing to test on the boot and bonnet lids, which would be the easiest to rectify if it all goes sideways. If it comes out ok...will schedule for after when I can get the doors dismounted and the shiny bits off the car.
Oh, BTW, he also uses this method at a couple airports near me for folks that want to strip their airframes without having to use the aggressive chemicals that are usually employed to get back to shiny aluminum (aluminium) in preparation for their refinishing. So, he seems to Get It, when it comes to helping in the renovation of high-dollar conveyances. We'll see.
But, first...just have to get the beast to the Brits at Bristol (RI) show on 6/10 at Colt State Park. Entered in the "Diamond in the Rough" class.
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Vinegar is an inexpensive rinse but the "Best practice" industry standard is Holdtight 102.
https://holdtight.com/products/holdtight-102/
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Cleaning is key, however the loose fibers created by the stripper are still in play, Europa TC said it best, veil and wait times . I am testing different veils that hide all hidden voids in the glass that I could not detect. After 1 year my upper body panels show signs of the loose fibers that are shrink wrapped by the clearcoat, luckily for me sanding down the clear and rebuffing solved the problem in the mirror reflection.
Dakazman