Painting over previous paint - primer or not

[MrTibbs]

Hi folks,

Thanks for the responses about rain on cellulose paint. I've got another quick question; I've been flatting back the existing clear, then giving it a couple of coats of high build cellulose primer (tetrosyl EP21), then flatting this back before putting the celly colour coats on.

The thing is, I'm running out of time to get any colour on the car this year (I'm already pushing it really, but I've got a half painted car and don't want to drive around in something that looks like a cut-and-shut.

I'm wondering whether it's necessary to primer the car before putting the colour coats on. The car is a medium metallic blue, and it's being painted in a dark solid blue. I did paint straight onto the flatted clear on the filler flap and it doesn't look like there's any difference between that and the parts I've primered.

I'm expecting to have to give the car a couple more coats next summer, and finish off the door shuts etc, but before winter really starts, was wondering whether I'm adding in steps I don't need to.

I don't want to do a bodge job, but there's no point including unnecessary stages.

What do you guys think?

 

[the snooper]

you only need to prime bare steel, if the paint on the car is sound just flat it and paint

 

[richie00boy]

Yes, in fact putting cellulose primer down first increases risk of reactions and sinkage. The original clear coat is actually a better substrate.

 

[steveo3002]

no need to prime if its sound paint already , key it up and paint

any rub throughs you can mist on some aerosol etch

 

[MrTibbs]

Thanks guys, that's what I wanted to hear. If there are scratches in the clear, I guess it's sensible to fill them with stopper or high build (with a very small brush or a nail or something), otherwise the celly will sink into them?

 

[steveo3002]

id sand them smooth

 

[langy]

id sand them smooth

Absolutely

 

[norsa]

Beware and this is where primer comes into the equation. ( oh, by the by. Though I like him and his approach to mechanics, I blame Ed China for this obsession that everything that needs painting needs priming first. as Richie said, it can cause more problems than it solves).
I digress. Yes flat the scratches out with a block 800 wet. If you go so deep that you cut through to the base colour, you will need to spot prime or else you will get horrendous ghosting where your celly attacks the unstable base.
Nick

 

[steveo3002]

yeah ed china aint too good at the painting is he ...grey scotchpad for everything and a coat of red oxide lol

if you do rub through on a scratch then mist some etch over it localy (not the whole panel) and then tickle the dry edges with some fine paper , wont take more than a wipe over really