Media blasting questions
 

Hello,

I'm to the point where I am ready to take my doors to the media blaster and I have a couple of questions. I plan to get it back from the blaster and get it in epoxy before I start bodywork. I should mention this is my first body working experience, if that matters.

- What is the recommended media? I've heard that soda needs to be neutralized and cleaned before moving to epoxy. Is this correct?

- I'm leaning towards epoxy, body filler, then high-build, and finally sealer. I know people seem to be in two camps of doing DTM bodywork first vs. epoxy first. It seems it would be easy to deal with bodywork first with clean metal then epoxy, but I see strong opinions in both camps. Any suggestions in order of operation?

Also, should I remove the trim around the outside window area or leave it alone? (The one that is sometimes chrome.)

thanks
Renard

Re: Media blasting questions
 

I have always done my own blasting. I would consult with your shop that is going to do the work. Make sure that they have experience in this type of blasting. If so they know what type pf media to use . Otherwise you will have more work for yourself. I would remove all body trim and moldings. That way they will not accidently blast those parts and you will have a clean slate to work on.
Vic

Re: Media blasting questions
 

i recommend sand blasting. the metal on these trucks is heavy enough not to warp. of course you need a blaster who knows his stuff with any media or they can warp angle iron with dry ice. i sand blasted everything on truck, in three stages, as i needed the parts, bed, cab and everything else.
be ready for surprises. i was totally shocked as my truk had been wrecked, probably in the 70s and bondo'd up rather well. i've driven apache trucks since the early 70s and know where to check for rust. over the headlight buckets was spotless. turned out that they had put new fenders on the truck, everything else was caved in cancer. i drove truk for 20 years prior to the resto.
i sprayed everything with epoxy asap. no prep needed for sand, other than blow off well and wipe down with w&g remover. harbor fright gun is fine for this, buy a couple on sale if possible. if you are fast and can do all the bodywork before rust comes back, that works. i'm in a more humid section of the country. if it's gonna be a while, epoxy now or spray the bare metal down with por15 metal prep, i've had good luck with metal prep for storage of bare fabrication metal for truk
definitely remove any trim. disassemble everything, you don't want to disassemble it later to find rust under whatever. leave no screw untouched

this is my drivers fender after blasting. probably an inch of filler in parts that i never knew about in 15 years of driving it. door and step were also damaged, not to this extreme

Re: Media blasting questions
 

Wow. that looks like a big dent to go straight to filler. I don't think any of the dents were repaired on my truck. I'm just hoping not to find more rust areas to deal with like where the gas tank was.

Re: Media blasting questions
 

like Ogre said..disassemble everything...
on my truck they used coal slag..its supposed to be very forgiving, but they still warped my doors...everything else turned out great..only use someone that has done a lot of vehicle blasting... and get it in epoxy as soon as possible..its drier where you are , but around here it would be solid rust in just a day or so without epoxy
ive soda blasted some of my smaller stuff in a blast cabinet..i just wiped it with mineral spirits followed by wax and degreaser..then primer

Re: Media blasting questions
 

First and most most important, they should show you current examples of work that they just did on sheet metal items including large body panels.

A buddy took a pretty nice but rusty Model A body down to the semi truck trailer shop that guys in the area had been having their frames sandblasted at and the dude who blasted it pretty well destroyed the body in the process of blasting it because he had no clue how to do sheet metal. He normally blasted 40 ft long trailer frames. The panels were warped to the point that they were beyond repair.

The powder coating shop that does most of the sheet metal including a steady flow of car bodies on rotisseries for shops in the area did have one very experienced guy that did all the large sheet metal pieces. The manager showed me several pieces that had been done that day or very recently and they all looked great.

Soda blasting usually only takes paint off and a very skilled operator can actually remove one layer of paint at a time if they want to. It doesn't do well on rust though.

Some guys like walnut shells as they say they don't create the heat that sand does.

Still sand with a skilled operator will get the paint and rust.

I agree, strip the parts down to the bare naked and clean any dirt and grease off before you take them in.

Re: Media blasting questions
 

I took my parts to a guy that all he did was automotive sheet metal - he used ground glass as a medium. Like others have said, you really want someone who knows what the hell they're doing or you'll have a real mess on your hands.

I talked to soda and plastic media strippers too, but the problem with soda/plastic is it really won't touch the rusty spots, just take the old paint off.

I tried the caustic bath treatment on a couple of doors, but in the end I had them glass blasted too.

The same day all the sheet metal was done at the blasters, I took it home and sprayed it with Southern Polyurethane's epoxy primer. Acid etch primers make me nervous and this product gets the job done well.

https://www.southernpolyurethanes.com/primers

Re: Media blasting questions
 

I just had all my body panels blasted and epoxy primed at a local guys shop. He does industrial stuff like big bridge pieces but also does a lot of car and smaller stuff. It all came out great and all ready for body work. This was on a 57 pickup. Nothing got warped. For me it's worth farming this part of the build out. Steve

Re: Media blasting questions
 

Speaking from experience over the past year....

I called the local hotrod shop and asked who they use to sandblast. I had the body blasted with the same folks they recommended and asked not to have them primer it.

When I got home, I went straight to Eastwood Epoxy Primer to make sure there wouldn't be any rust. I probably sprayed it a week after I got the body back. Can't say enough good things about the $16 purple spray gun at Harbor Freight for this.

Now a year later I'm putting finishing filler and paint on here's what I would have done differently...

1. Hit the whole body with 180 grit. Just knocks off the peaks in the metal left behind by the sandblasting
2. Do the sanding because you'll want to go over the whole thing with wax and grease remover or all prep. I didn't do this step and saw rust coming back in some of the pits. When I first tried doing this without sanding first, the peaks in the metal just tore my microfiber cloth apart leaving behind tiny fibers.
2. Air gun and shop vac EVERYWHERE. I am still finding media hiding in places haha
3. Don't sweat dust in the air or laying on primer perfectly. Just get it on there because you'll definitely be sanding every surface later multiple times before paint.

I've read differing opinions on what to do after primer, but I went with what two of my local body shops and one hot rod shop told me. Modern epoxy primer is ok to lay fiberglass filler over. but you can also do DTM if the metal is new and super clean. Over primer Just scuff the primer with 180 grit and away ya go. Modern filler like Evercoat Rage should also lay on primer because it is porous and may trap water between bare metal and the filler. I like to think I'm making a sandwich on top of the bare metal. Primer seals the metal for as long as I want to take doing filler and body work..primer/sealer is also at the end before color leaving all the body work sandwiched between two primer steps.

I've been happy with my research and results but had to "redo" some of the steps above at a later date.

https://live.staticflickr.com/65535/...6c8729f5_c.jpg

https://live.staticflickr.com/65535/...8f01f6af_c.jpg

https://live.staticflickr.com/65535/...bc6aa112_c.jpg

https://live.staticflickr.com/65535/...d73636d6_c.jpg

Re: Media blasting questions
 

Thanks for all the responses. I think I have a guy that knows what he is doing (hopefully). He's in Golden and here's his web page https://a1metalstripping.com/

I've talked to him on the phone a few times and he seems to know what is going on with these old vehicles. I'll talk to him about my plans and see what he recommends re media. He seems to have a steady line of business because he's backed up several weeks right now.

I'm leaning towards the process Gigamanx posted. I don't have any idea how long its going to take me to do bodywork, so I best get it in primer first. The doors are completely stripped right now except for the small trim on the outer door around the window. I'll remove that too.

Thanks

Re: Media blasting questions
 

DO NOT SAND BLAST UNLESS YOU KNOW THE PEOPLE DOING IT REALLY KNOW HOW TO SAND BLAST SHEET METAL!

I can't make this clear enough, YES this metal will warp when sand blasted wrong, YES IT WILL WARP. And we aren't talking "oh damn I have some more work to do" kinda damage. We are talking "HOLY **** I HAVE TO GET A NEW DOOR!" kinda damage!

I have seen it over and over, and I have had had it happen to me. A 1928 Buick door, HOLY CRAP it was DESTROYED by a sand blaster. It looked like a friggin bag full of bowling balls!

If done properly, yes it can be done, but you REALLY need to find out if the people who are doing it know how to sand blast vintage car body parts not just stair railing and farm tractor frames.

DO NOT SAND BLAST UNLESS YOU KNOW THE PEOPLE DOING IT REALLY KNOW HOW TO SAND BLAST SHEET METAL!

Did I mention........
DO NOT SAND BLAST UNLESS YOU KNOW THE PEOPLE DOING IT REALLY KNOW HOW TO SAND BLAST SHEET METAL!

Brian:mm:

Re: Media blasting questions
 

By the way, it doesn't warp metal as I thought for years and many others think, from heat. When you are sand blasting in the dark you will see sparks as the sand hits the metal, that sort of thing is what gives us the idea that it's "heat" that warps the metal. But it is not heat at all, in fact if feel metal after you sand blast it it's often cooler because you have been blowing air on it.

No, what causes the warping is that each one of those little rocks that hit the metal is like a little hammer. They thin the surface of the metal where they hit. So when you hit the metal with millions of pieces of sand you are hitting it with millions of little hammers thinning out the top layer of the metal! When the underlying metal isn't thinned, it warps the metal. Of course if the metal was being thinned all the way through it would warp it too, just different than what the sand does.

Just be careful, be sure you know they know what they are doing before you hand over those treasure body parts to them.

Brian

Re: Media blasting questions
 

and then there's martinsr's thoughts :haha::haha::haha:

Re: Media blasting questions
 

I have done my own sandblasting on several automotive projects. the trick is to keep moving and stay back from the surface. hit the surface at an angle not straight on. don't concentrate on a particular spot till it is bare and clean, move the blast pattern around the project and just keep hitting that spot time and again till it's good. also vary the angle so you don't always hit part "A" at a 30 deg angle from the same side, this way you get all the "shadow" areas. sandblasting also leaves a profile on the surface of the steel, like the surface of a piece of sandpaper with highs and lows. if you don't sand it before epoxy then the tops of those craters can stick up through the epoxy layer, like a mountain top through the clouds, and become the bare steel that turns to rust. I recommend to hammer out some of the larger dents before you blast, even use a disc grinder with the sand disc to remove known filler areas, then blast, then sand with something like 180 grit to knock off the mountain peaks, then wipe it down with wax and grease remover, then epoxy right away to seal it. let the epoxy cure well and then do your hammer and dolly to get the shape back before any welding which will also try to reshape the project part. it may even be a good idea to fit the part where it will be to ensure it still fits before going further with weld repairs etc especially for fenders and stuff that can be mishapen but looks right until you hold it up where it fits. better to get it shaped right before it has a chance to warp I think. then after welding and hammer/dolly/metalworking re-epoxy before filler. because filler is porous it can allow humidity to hold under it and cause rust. I always try to ensure the filler goes on top of epoxy. primer surfacers are also porous so it is a good to know your product before you spray so you have an idea of what to expect. if you do the bodywork and expect to have the project sitting arond for a bit of time before paint it could be a good idea to re-epoxy after the bodywork is done so it is sealed. thin the epoxy so it latys out smooth and will take only a bit of work to sand it before sealer and paint.
I know guys who spent time and money on sandblasting stuff, like machinery or trailers, and then sprayed primer on the parts friday night before heading out, thinking it was sealed. well, primer isn't always a sealer so the stuff was rusty when they came back after a weekend off.
talk to your blaster to ensure they have done bodywork with success. see some pics or actual stuff they have done on sheet metal if possible. they may even offer to epoxy the parts for a fee but then you don't get to see how good the blasting was. anyway, blast, sand, epoxy seal, thats how I do it.
good luck, post up some before and after pics.

Re: Media blasting questions
 

Has anyone tried the Dustless Blasting, as seen on shows like those from Powernation? I was wondering how that type might work out.

Re: Media blasting questions
 

Thanks for all the comments. I dropped the doors off today and spent some time talking with the owner whos been in business since 1982. He has one guy who only does automotive parts. He understood the concern with warping. He said "I can't say in all the years, we haven't made a mistake, because we have. But not often" He went on to say that these vintage vehicles were less susceptible to issues and the older foreign made cars with really thin sheet metal is where he usually has concerns. He recommended a media called Starblast. He showed me some work and the finish that it would end up with. Will report back with how it goes and snap some pics of the finished work. Thanks.

Re: Media blasting questions
 

don't personally know anybody who wet blasted but there have been a few guys on here who have done it. my problem is wet sand will still get everywhere and take some time to dry out I would presume. the metal gets treated with something to keep it from rusting but still, goes against what my brain says, haha.

Re: Media blasting questions
 

Martinsr i agree with you 100% there is no heat in blasting to warp the metal. IT'S the peening of the sand that dose the damage. the two important things when blasting is the air pressure and the grit of the sand. coarse sand and fine sand at the same pressure will have two different outcome

Re: Media blasting questions
 

I just bought one of those wet blasters that they advertise on FB that hooks to your hose on your pressure washer. Haven't tried it yet because the pressure washer has carb issues but I intend to try it on smaller pieces that don't fit in my cabinet.

Dang, now that I have survived my daughter's wedding fixing that pressure washer is back on the to do list.

Re: Media blasting questions
 

I did the dustless blasting and am VERY PLEASED. Two guys working, blowing wet glass beads while I dealt with the wipe-down and spray of a chemical they provided named After Blast. The process removed all paint, undercoat, Bondo, rust, and left me with bare metal. The best spent $1,000 of my life. Bob It's a '38 Packard I'm also working on while doing my '55 big window

Re: Media blasting questions
 

i checked into the dustless blasting..the closest one to me was 40 miles away...he wouldnt travel..said if i brought it all to him he would do it but wanted $2000 ...no way..
as far as the leftover media from the blaster i used , i had mine on a rotisserie ..i bet i rolled it 50x dumping media..all while using a air hose and shop vac..im confident i got 99% of it out

Re: Media blasting questions
 

I've been wondering about the pressure washer type sandblasting kits you see on FB, amazon etc. anyone have experience with these?

Re: Media blasting questions
 

grrr!!! that's sexy :D

http://67-72chevytrucks.com/vboard/a...1&d=1629401823

Re: Media blasting questions
 

I purchased one of Harbor freight 110lb pressurized abbrasive blasters they sell, and also one from Tractor Supply they are identical and the same company who makes them,
That being said i went on youtube and found modifications to make them work better (WAY BETTER) in fact! I use Black diamond "fine" Media and have an IR 80 gal 7.5 HP 2-stage compressor and then have it piggy backed to a Sears 40Gal 5.HP single stage compressor. with this set up i can run the Black diamond media for about 20-min or longer and i did all of my 58 Cameo Bed, Cab, Front fenders, this system i have has worked out great, and as Crazy as this sounds, I enjoy media blasting Lol..
havent had any warpage at all, and i would say yes,keep the nozzle moving and at an angle,i think a key factor also is the metal is a heavier Gage steel on these year trucks!
it would probably do some Damage to my Wifes KIA, Lol....

Allen

Re: Media blasting questions
 

i had a dustless blasting company come and blast my cab, what a mess. i have taken (2) 5 gallon buckets of glass muck out of my cab after they left. i had automotive restoration in Brookfield. WI dip and e coat the doors. fenders, frame and some misc parts they came back beautiful. i didnt do the cab since it was too big to fit the e coat line (52" height restriction) the frame and door especially all coated inside and out wit epoxy e-coat. i wouldnt dustless blast again for all the tea in china.