Friday, January 13, 2012

Guide Coat 101

What the... ?

You gotta be kidding me!

OK, here's the deal.  A Guide Coat does two things.  It insures flat surfaces and it identifies low spots.  The process requires a contrasting paint lightly sprayed over primer followed by block sanding.  We want to leave as much primer on the car as possible but we also want to remove as much as necessary to get a flat surface.  To achieve this we only block sand until the guide coat is removed or until we expose fiberglass.  When either one of these occur we stop sanding and move onto the next area.

Lets get started.  After block sanding this fender for just a few minutes we have mostly flat surfaces (green) and a few low spots (guide coat).  A few more swipes with the sand paper should remove several of these low spots.

And that's exactly what happened.  The front part of this fender is very flat and smooth.  Any thin areas of primer will be corrected when we shoot the car with the next full coat of primer.

The rear part of the fender will need additional work though.  We have low spots and we have exposed fiberglass.  Since we can't sand this area any further we will probably apply a thin coat of Bondo to correct.

These low spots are super shallow and will be filled in with the next coat of primer.

Click on this picture and check out the results.  Do you think the next coat of primer will fix the low spots or do you think they need a little Bondo?  It might be a combination of both. 

The front is turning out very nice.  The raised center section may require a little Bondo.

Nothing major back here.  The next coat of primer should fix these imperfections.

There is a lot left to do including the door jambs, drip rails, hood jamb, window jambs, and everything below the center line.  When we are done we will shoot fresh primer on the whole car again followed by more Guide Coat.  We will continue this process until all the surfaces are flat and all the fiberglass has primer so expect several postings about guide coating.  One thing for sure is the results are already pretty awesome.

Thanks for watching.


  1. So all this pre work on the primer must cut down a ton of work on the final blue coat correct ? Jim

  2. Correct. All the prep work is in the primer. Once that is done it will only take a day or so to shoot color. All the hours are in the primer.