I've always used a relatively coarse grit over existing paint to key new paint to - a finer grit leaves a smoother surface that the paint might not grip to as well.
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I've always used a relatively coarse grit over existing paint to key new paint to - a finer grit leaves a smoother surface that the paint might not grip to as well.
Quote:
Originally Posted by Judo
The product (ie- all product, paint primer, etch etc) needs a 'key'- or a surface upon which to fasten itself. A flat surface offers only a flat key- ie, not much surface area relative to adhesion. A properly keyed/sanded surface provides millions of little nooks and crannies upon which to offer adhesion- which is both a product of chemical bonding and surface tension.
I'm of the school of thought that leaves filler (bog, polyester fill) with a course key- I leave this in 120 to 180 grit. Then I apply a primer then a spray putty (high build)- leave this for days if you can. Leave the most 'key' that you can get away with...
Apply the putty as a dust coat then really pour it on- depending on the underlying surface - whether or not 'straight and flat' are high priorities for you. (this is whole new thread of conversation).
Then apply a guide coat (just some dark colour dusted over the top). Then start with 320 grit paper (depending on how much surface you have to sand- you can start with 240 grit if you wish (over the dried/cured spray putty)- get it flat- note all those high and low points.
For solid colour (ie, that is, non metallic colours) you can leave it in 320grit. That provides a lovely key.
For COB metallic acrylics (clear over base), you can leave it in 400grit, but I prefer to leave in 600 grit prior to applying the colour.
remember that if you are painting over someone else's work (like, old repairs from years ago or whatever)- that is always going to be risky.
It's best to take it off and start from scratch (literally).
Follow a few rules with respect to product and surface dynamics (some of which are briefly detailed above). Don't be afraid to ask.
What original poster said (below) is the best way to do it- list what you need to do, list your product preferences, ask for advice.
For backyarders and beginners, acrylic is your friend. Leave the two-pac for those that have access to ovens and breathing apparatus.
I made some notes from an episode of Dream Car Garage.
Dream Car painting guide
1) Bare metal.
2) Epoxy primer. Generally no sanding at this stage. Bonds to aluminium, steel and fibreglass.
3) Polyester coat as sprayable thick body filler. Sand 120 to get ripples out. Finish 320.
4) High build (high built?) primer. Sand with 320, then 400 and finally 600 wet.
5) Colour coat (aka base coat). Total thickness of all coats at this stage 13mm(!?). Solvent soluble paint in the case of Dream Car. No sanding this layer.
6) Four layers of clear coat, adding another 3mm (!?) to thickness. Sand using 1,000 then 1,500 and maybe 2,000 wet. Sanding may take about 1mm off thickness.
7) Polish clear coat using chemical compounds. Polishing may take 1mm off.
Great info here guys.
I'm not needing a show-car finish. Just presentable.
So what's the deal with paint incompatibility? Are primers and etch primers only suitable for one type of top-coat (arylic vs enamel) or are they universal?
I suppose I could test this relatively easily myself.
Should it say it on the can? :)
Was in the hardware trying to read the label on a half litre tin...asked a sales assistant if she could read it...response, shall we get a bigger can then?
It would be easy if they did.......Quote:
Originally Posted by workingonit
I've proven the plastikote etch primer and septone primer/filler aren't compatible.
They bubble up and peel off leaving perfectly clean aluminium. Which is strange because I'm sure I've used them together before.
formulae change and therefore some incompatability ?Quote:
Originally Posted by Dougal
Plastikote was the best spray can paint pack product I've ever used - currently disappeared from the Oz market due to Wattyl (the Oz agent for Plastikote) not importing it and introducing their own (IMHO inferior) copied product. I suppose it could be the same thing with double the thinners but it's definitely not as good.
Never had much luck with any of Septone paint strippers - maybe their other stuff is OK - I haven't tried it.
The can of Plastikote etch is the same can, I bought it for that job about 8 years ago.Quote:
Originally Posted by 87County
The can of Septone I'm only 50% sure is the same Once I start sanding off the colour on that panel I should reveal at least the primer colour underneath and that'll complete the mystery.
I have access to all the usual spray gear and I've done a bit of spray painting before. But mostly with machinery enamel.
It's more this is a job of the size it's not worth getting paint mixed then clear, thinners and all the cleanup.
If I was doing more than one panel or required an excellent finish I'd be into the spray gun. This is more tidying up the worst corner of a vehicle body I'll only have for a few more years.
The body I'll be swapping over to is a different shade of white. The same shade as my third rangie. For those two I will be breaking out the spray gun. Once everything else is attended to.