Re-finishing help - spraying over existing finish

5redlights

I'm looking to do a re-finish of a pacifica, so want it to be quick and cheap. 

Would sanding the original finish lightly (to give the new finish something to stick to) and spraying new finish over the top work? I'd probably be using nitrocellulose spray over the top of poly. Is that doable? It would be black over white. 

Thanks 

Corvus

Totally do-able; degrease it first, panel wipe is the boss but lighter fuel will do in a pinch. You want any old wax and fingerprints etc gone before sanding, otherwise it gets stirred and mashed about. Handle with gloves. Tescos white kitchen roll is surprisingly lint-free (don't get the ones with printed patterns on).

Sand with 800 grit. Might have to deal with scrapes and what have you with coarser paper first, or spot fill and all that.

One thing with black, it shows absolutely every tiny microscopic imperfection loud & clear - if that bothers you. Folk often assume it's easy and hides everything, but the reverse is true.

randella

With nitro, it does go on pretty thin.  When you're wetsanding and polishing at the end you won't have much to play with so get a couple more coats on than you think you need.  It'll prevent the tears of pain when you go through the black to the white!

Take your time, lots of thinner coats rather than one heavy one.  Wear a decent mask, that nitrocellulose stuff's bloody horrible.

Apologies if you know all this already

munckee

I've sanded poly finish 600 grit and then spray painted and then used poly spray over the top worked fine.  Not sure about nitro on poly.  I did it in a garage with the door open and made a cardboard spray booth and hung by fishing wire from the ceiling.  3 coats of paint, 5 very thin coats of poly spray (from halfords).

5redlights

Thanks for this. I've done nitro finishes on necks before, but for bodies always used stains or oils , so this is helpful. So clean with paint prep wipe, sand with 800 grit and wipe down, spray thin coats of Black nitro, then clear nitro to seal, then wet sanding and polishing. 

randella

5redlights said:

Thanks for this. I've done nitro finishes on necks before, but for bodies always used stains or oils , so this is helpful. So clean with paint prep wipe, sand with 800 grit and wipe down, spray thin coats of Black nitro, then clear nitro to seal, then wet sanding and polishing. 

Yep, that's about the long and short of it

Corvus

You don't need the final clear with a solid colour, you can go straight flatting & polishing up a solid colour. Just squirt enough down to take the sanding & polishing up.

randella

Corvus said:

You don't need the final clear with a solid colour, you can go straight flatting & polishing up a solid colour. Just squirt enough down to take the sanding & polishing up.

Fair point, the clearcoat can make a difference if you're going to eventually try and 'vintage-up' the finish with colouration over time, but I suppose it's going to make the square root of naff-all difference to black!

Corvus

It can give a different look if there's enough laid on, like a more glassy deep type thing, but straight black polished up looks great too. Both ways do (for about 2 mins anyway till the fingerprints / doghairs / beer drops land )