Daily Archives: November 1, 2012
Posted by Jonathan
Today we spent the day working on the Plymouth Satellite, getting it sanded and in primer before the exposed raw metal could begin to rust. It’s not good for my reputation to have a car rust while sitting in the shop ya know.
The first two pictures show Chase welding up the antenna hole on the fender. Being that this is a Adam 12 police car replica the antenna had to go. The cops would listen to the radio … but not the radio attached to this antenna.
We filled the hole in picture three too, but it wasn’t an antenna hole. That’s a rust hole. It’s a small one, easily fixed, but this is why you sandblast these old cars. Fixing it now, before painting, prevents it from spreading and causing problems later.
Pictures four and five show one of the fenders being sanded. If you look at the fender in picture five you can see that the fender has a vertical line down the middle over the fender arch. The left side of the fender has been sanded, the right has not. This is a visual example of why we sand bare metal before applying the epoxy primer. By sanding the metal we rough up the surface so the epoxy can really get it’s teeth into the surface for a tenacious grip.
Not only did we fill all the holes, both intended and unintended, we also did some rough repair on a small dent. The dent in picture six was fixed the old-fashioned way. The “modern” to pull a dent is to weld a stud, in effect a big copper nail, to the sheet metal and use a slide hammer to tease the metal back into shape. You can see from the two studs sticking out that we did use the slide hammer some on this dent … but most of the dent was pulled by drilling holes in the metal and inserting a slide hammer into the holes and giving it heck.
Both repair techniques work on the same principle, using a sliding weight to transfer impact forces from the tool to the sheet metal, but the slide hammer can apply more force using a screw drilled into the bodywork than the slide hammer on a stud can. You strike the anvil part of a slide hammer hard enough using a stud and the stud simply comes off the car. Do the same with a hook or big screw drilled into the car and something is going to give. Think 14oz claw hammer vs. a 5lb sledge.
After the fenders were, ahem, knocked into shape, we turned our attention to the hood. Chris is sanding away on the hood with the DA (Dual Action) sander in picture seven.
Picture eight shows the three pieces all lined up in the booth for primer. The first primer to be applied will be the epoxy primer. This primer is designed to bind to bare metal and provide a tough protective layer over the metal to prevent rust and damage. Every job at JMC AutoworX starts with the epoxy primer if we are painting over bare metal.
After the epoxy primer has a chance to dry a bit we then apply the Evercoat 4:1 High Build primer. This coating is like sprayable body filler and is used to cover and fill small imperfections in the metal. Not every car will get this high solids primer, but when the owner wants a finish that is a step above the rest, this is the way to get it.
The last thee pictures, numbers 9, 10 and 11, show the fenders and hood after the application of the high solids primer. Most of the material applied to the car will be sanded off by blocking the car. Blocking is when a length of sandpaper applied to a semi-rigid plastic block is used in the sanding process. The block allows the sandpaper to really dig in on the high areas while lightly skimming over the low areas. This has the effect of smoothing and leveling the surface of the car until it reaches a glass like smoothness. Blocking also prevents imperfections from appearing in the primer during sanding from the ridges and angles of your hands and fingers.
You might be wondering why, if the high solids primer is only for smoothing small imperfections the dent that was pulled in the fender wasn’t repaired first. After all, if you look closely in picture nine you can see where the repair was made. The reason is two fold.
First, yes, obviously the high solids primer can’t fix big dents like the area we repaired on the fender. It’s good stuff, but it isn’t that good. What is not so obvious is that it can’t really fix even small dents either. During the blocking process some small dents may be discovered that will require additional repair work. The high solids primer is very good at locating small dents that may not be noticed and smoothing tiny imperfections that can’t be seen until after the car is painted. But it isn’t designed for dent repair. Since we are likely to be fixing dents anyway, there is no need to do dent repair twice.
But there is a second reason for doing even obvious dent repair after the car is blocked, and that reason is time. There is only so much time available between coats before the adhesive effects of the layers are lost. In other words, if we wait to long between coats, while we do dent repair for example, the high solids primer won’t properly adhere to the epoxy primer without sanding the epoxy primer first. Trust me, we do enough sanding on these cars as it is … nobody wants to do more sanding than we absolutely have to.
We will let these parts dry over night and then tomorrow we can get to work sanding most of the high solids primer off. It’s a good thing I love my job or all this sanding could get tedious.