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MG MGB Technical - To sand blast or not

No doubt this has been covered before but with new products around perhaps there is new thinking.

I was going to blast my B but a friend has advised me not to, just clean prepare and paint.

What is the current advise?

TS KING

I agree with your friend. Do not sandblast.

Sandblasting will embrittle steel panels and make them more
prone to cracking (see: "crack of doom" elsewhere in this BBS).

Also, it is very difficult to remove every grain of sand from every
nook and cranny prior to painting. Sand will promptly jump
from their hiding places onto freshly sprayed panels, however.
Daniel Wong

Soda blasting (using sodium bicarbonate) seems to be the new thing. Results are astounding and no warping of panels.
J Tait

I just got an estimate of US$600 to media blast my roadster with baking soda, including the underside of the hood. The door jambs, interior, etc. would be extra.
The powder residue is minimal and the finished metal can be left bare for up to 4 weeks while more work is done, then has to be primed and/or painted.
It takes some serious compressor power and big bore lines to do the job. A friend used a bag of media to clean up a motorcycle tank using an Eastwood kit. The guys I visited estimate 6-8 bags of media for the 'B.
I should be sending it to them in 2 weeks for stripping and bodywork. The floors, doglegs and floor pans have already been replaced.
You can also use chemical strippers; I worked with someone who stripped a big Buick with chemicals and then prepped and painted it in his garage. The finish is terrific; he's an old time hot-rodder and knows how to do it all.
Andy Taylor

Sand is way too aggressive and soda is the current thing, although mine was chemical stripped.

The 'crack of doom' is something completely different and caused by misalignment of the 1/4-lights to the screen along with a design defect in the doors, and is a vertical crack in a particular place of the door skins.
Paul Hunt 2010

FWIW,I had mine acid dipped and then E_Coated.Has done well,Rich O
rich osterhout

Thank's guys
A friend has advised I use a DA sanding disc but that sounds a bit too aggressive for my liking.
TS KING

Soda is probably the way to go now although 10 years ago I had my roadster sandblasted and have had absolutely no trouble with it neither have I had media coming out of the cracks. However if a flat panel is to be blasted the gun must be held at a distance otherwise the panel will warp.
Iain MacKintosh

Might I suggest that it's much easier in the end if you have the body blasted with dry ice? Blasting with dry ice involves using a crusher to pulverize a block of frozen carbon dioxide into particles that can then be used like any other blasting medium. Since the particles of dry ice evaporate when they warm up, all that remains is the material that has been blasted off, i.e., a fine dust of paint and rust. The advantage for the restorer is that no blasting grit remains stuck in seams, nooks, or crannies. The bulk of the remaining fine dust can be removed with compressed air, and what little remains on the surface can be removed by simply wiping it down with a solvent-soaked rag. The advantage for the blaster is that he can adjust the crusher to pulverize the dry ice to whatever size grit is appropriate for the job, and he has far less stuff to dispose of after the job is finished.
Needless to say, the EPA and the environmentalists love this technology. The downside is that, as it really isn't practical to try to store a block of dry ice at the work site, the dry ice has to be delivered to the site soon before the blasting is to take place, plus you need an expensive crusher, so home workshops really can't use it. The technology is mostly confined to businesses that do a lot of blasting, such as scrapyards that specialize in reclaiming stuff for automotive use. It costs more up front, but the environmental and disposal problems are greatly reduced, so when working on a large scale, it's practical and more convenient.
Stephen Strange

TS

Media prep is the best way to have a good understanding of what is under all the paint on your car. If your body is in good shape and you have the original paint, using a DA sander with 260 grit paper can get you a good base for repainting. That is what we did with my 67. Sanded the old paint, finished any low spots and repainted in the same color.

Sanding is a couple of days work, but something you can do yourself. Go to a library and see if you can get a book on paint prep.

Andy's example above is a good deal in my opinion. I would gladly pay $600 to have the body all ready painting.
Bruce Cunha

This thread was discussed between 28/05/2010 and 30/05/2010

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