How To Prep A Car For Painting

How To Prep A Car For Painting

Gary Dorman explains the process of preparing a repaired car panel for re-spraying, including priming, guide-coating, masking, cleaning, and appropriate blending of colours between panels.

Now, the car body repair's all done, it's all in primer, it's all looking nice. Before rubbing this down, before we spray it, we put a guide coat on there. It's basically, in this situation, an aerosol black. Just so that when you're rubbing it down, any little impurities will show up a lot easier because it will show up as dark in light. Give the aerosol a real good shake. Make sure you're well ventilated. Just dust it on over the primed area. Now that it's there, when you go to wet flat that all down, any little naughty bits, you can sort them out. That's the guide coat. It's now ready to be de-masked, re-masked up for the rub down and sprayed. Now's the time to de-mask the masking paper and masking tape and to re-mask for painting the panel. This area is in primer to do bodywork on the metal side of things. The base coat is the colour, the clear is the lacquer, which seals the whole area off and pulls it all in so it all matches perfectly. We've kept the area as small as we can around the damaged areas. We're going to mask this up. Then when we spray, I'll be painting this area here where it's grey and black and I'll be blending the colour up into this top edge and over to here. Keep it nice and small. Blend the colour through. And we will mask the door off so we spray the wing only. If we don't mask the surrounding areas, we will cover it in over-spray, and on a sunny day, it will look absolutely horrendous so you need to make sure you cover the other areas off. Get the edge masking tape. Pull the tape down. Make sure you get a nice edge. Because we're spraying the door here, we need to cover all this area up. For all auto body car repairs, the biggest problem is overspray. So always make sure you cover all the surrounding areas really nice. We use a machine. When we pull it off, it already has the masking tape on the edge. If you haven't, use a bit of newspaper or a bit of brown paper or a bit of wallpaper. This will make it all nice and neat. Because we're spraying the wing, and not the sill section, we'll mask this area off as well, making sure we go as far into that edge as possible, not to get any over-spray on the surrounding panels. That area around the bottom will again be masked off. The car is a bit dirty. Under normal circumstances, we'd make sure it was all cleaned beforehand. The car is all prepped up, all in primer, all guide-coated. Now, we need to wet flat this down, get this all lovely and smooth and clean, all ready to be sprayed. I'm using P800 wet-and-dry. If it was a larger area, I might use a 600, but 800 will be fine. Because this is metallic, you've got to go quite fine or the scratch marks will come through. Whatever the paper is, fold it in half. We do this wet. It can be done dry. So I've got a bit of 400 dry. Knock the head off with the 400. You could prep it up all the way through with the 400 wet-and-dry, but we like to go a little bit finer. That's that done with the 400. Now, I'm going on to the 800, to get the last bits of impurities taken out of the bodywork. I prefer the wet flat in, it doesn't cause any dust and when you're spraying, the biggest problem you've got is fighting against dust particles getting onto the paintwork especially on these light colours. Once all the guide coat is gone, we look at the comparison between this and this, and we can see a little bit of the guide coat. For surrounding areas, I've got a 2000 which I would normally use for polishing the car with. Because this paper is so fine, you don't have to cover this with colour to get rid of the scratch marks. And now, I've got a grey Scotch Brite to nib off. I'd normally do it damp but this seems to cut in a little bit nicer. I will Scotch over the whole panel, just taking any little impurities sitting over the top of the paintwork. All we'll do is put lacquer on top and this will stop it from flaking. If you go on top of shiny paint, there's a very good chance that it will flake over a period of time. All metallic colours have to be painted and blended. So you put the base coat on, blend the colour out, and then you lacquer the whole panel. So where it's been rubbed down with the 800, that all needs to be put into the base colour - the blue silver - and then you flip the paint out, keeping it away from these areas here and up here, because if you get too much build-up of a colour, the colour might show out from one panel to the next. I do the spray using my hands. Get the clear, lacquer the whole panel, wipe it over with a clean cloth and there is the car body work, all prepped up. This is a tack-cloth. It's a sticky cloth. Before you spray your car, you get all the area cleared up. You blow the area off, and as you're blowing it, you put this cloth over the whole thing. And what this does: any top layers of dust and little marks that have been left by residue that you haven't taken off before will come off now. And that is it, now all ready to be sprayed.