Hi Folks,

Sandblasing the undercarriage, wheel wells, door jambs, etc. is fine, but blasting the exterior panels of any vehicle, regardless of whether it's vintage metal, which is normally a heavier guage, or the newer stuff sh0ould always be avoided.

Heat is not the problem. That's a myth. It takes very close to 600 degress F in a localized area to create distortion from heat. What happens in this instance is that the heat causes the metal to expandand since it has no place to go, the forces involved of the expanding localized area of metal pushes itself into the surrounding cooler metal. When it all cools to the same temperature the heat affected zone had in effect become shrunken (less surface area than what it was originally. Sandblasting does not create that amount of heat.

The trouble lies in the amount of pressure being applied by the millions of particles of sand peening the surface of the low crown panels. There isn't enough strength to withstand the abuse and the metal looses the battle and begins to stretch as a result of the peening action. Even high crown panels of vintage automobiles can be affected by this, although not normally as noticable, nor as critical.

I've seen many body panels absolutely ruined as a result of sandblasting and would not advise it, even if the operator "claims" to know what he's doing. As I said, it's fine for areas where there is sufficient strength to withstand it, as it will cut down on several hours of cleanup time in those hard to get to areas.

As for the plastic media blasting, I've seen it stretch low crown panels as well. For the most part, it seems to be more forgiving than sandblasing, but still a risk involved.

Soda blasting is also a popular method, but be very careful toi cleanup the residue left behind before refinishing. This residue will prohibit your primer from bonding to the metal ans you will have a real mess on your hands when the paint starts blowing off in large sheets. It's always a good idea to sand all area to be repainted with 80 grit sandpaper where possible and a red scotchbrite pad in those hard to sand areas.

For optimum corrosion resistance and adhesion, a high quality epoxy primer is the best coating available for use on bare metal. I've been a professional painter for nearly 20 years and the best I've found is available from Southern Polyurethanes Inc. www.southernpolyurethanes.com

John,

My recommendation would be to remove all the trim, door handles, lights, bumpers, etc. Wash the body thoroghly with hot soapy water (Joy dishwashing detergent works great) Get everything you can, door jambs, underside of hood & decklid, etc. This will remove water based contaminates that Wax and Grease remover will not get. The next step will be to use a good wax and grease remover to kill any remaining contaminates. Follow manufacurers directions for application and clean-up.

Any areas that need aggresive sanding, such as rock chips, scratches, etc. should be feather-edged with 180 grit paper on a DA sander. If you have dents that need repaired, those should be taken care of as well and if you need to use body filler, make sure to prime those areas before going on to the next step. It's best to use epoxy primer over bare metal areas prior to applying body filler as well as applying two coats of epoxy over the top of filler. I prefer to metalfinish everything, so filler is not needed, but it takes several years of practice to master that, so I understand is you need to use filler.

Once you have the repairs made, get a fresh bucket of hot soapy water and 600 grit wet/dry sandpaper and sand the entire area you plan to refinish. You do not need to remove the original paint. In fact, it's the best base you could hope for. You will remove most of the oem finish as you sand with the 600 grit anyway, as there will only be a very thin layer of it left at best. The oem primer is what you really don't want to go through as it has a great adhesion to the metal and has great corrosion resistance. After sanding the car completely with 600 grit, get another fresh bucket of hot soapy water and use a good amount of Ajax with a red scotchbrite pad. This will get any area's you may have missed with the sandpaper and will have the body ready for a fresh paint job. Make sure to rinse the body several times to get rid of any sanding sludge that may be lodged in hard to reach areas. This will have the car ready for the painter or if you decide to do it yourself at this point, you can simply mask it off and go over it one time with a final wash solvent prior to painting. A good wipe down with a tack cloth and you'll be ready to paint!!

Good luck with it.

Randy Ferguson
Ferguson Coachbuilding
Robinson, IL.