this problem. Ive been in panel and paint for 25 plus years so sinkback is no real mystery to me but what im looking for is a primer or sealer that actually works. Main problem being customers with old cars panited in dulon type products wanting there cars painted but dont want to pay to have them stripped first. You can warn them but it seems to fall on deaf ears till a month after painting with modern finishes they have sinkback. Dosnt seem to matter if you use epoxy primer or just normal 2k it still happens. They say there are primer that will seal off old paint and repairs so do you guys know what ones they are! Even though I know I would like to hear your reasons why this happens, in case my info is wrong LOL.
banty,
Nov 5, 7:39pm
A mate of ours just did his own vehicle and let the primer harden for over a week, it meant it was harder to rub back but he got a primo finish no sinkback at all. Time's not a luxury you always have though especially in business.
Not for use as a final primer though as it would take a long time to fine sand lol.
But as the first barrier coat on a situation like you have described, then I would recommend it.
As in 2 heavy coats of it, then block down with 80 then 150, then apply a good 2k primer surfacer over that.
To be honest though, I don't reckon there is any thing out there that is guaranteed 100% to not sink even a little bit, when going over lacquers or 1k enamels.
The heat of then sun itself, will cause lacquer to shift when it's trapped under a super hard 2k sealer.
gunhand,
Nov 5, 8:21pm
Interesting product, and yes you are dead right about no real gaurentee it wont happen.
jason18,
Nov 5, 11:33pm
What is sinkback!
gunhand,
Nov 5, 11:37pm
Sinkback is the fuzzy lines and scatch marksyou see in paint work. it appears around repaired areas mostly. And its when you try and paint over old paint systems with new.
franc123,
Nov 5, 11:42pm
Its the exposure of minor scratch marks and sometimes even more serious defects in the final coats of paint, caused by the continued drying out (and thus solvent loss) out of the primers/primer fillers or topcoats thus causing these coats to lose some of their "body" and ability to cover these defects.They may not show up for days or even weeks after the final coats of paint are sprayed, even though they looked good immediately after the primer was flatted off prior to topcoating, especially over areas that have been filled or where spot putty has been used.I've always tried to avoid it by making sure puttied areas have been left at least 24hours before attempting to sand them back, ditto with the primer coats, and wet sanded with 800 grit at the coarsest prior to topcoating
jason18,
Nov 6, 12:03am
Ah yes have seen that in my valiant. Seems so smooth when you do the.final sand down and lay some paint on ya think wtf where did those scratch marks come from haha. Doesn't really worry me tho.
attitudedesignz,
Nov 6, 12:09am
AAA (Dulux / PPG) thinners was / is guaranteed to show ANY sinkback problems within seconds.i HATE AAA thinners LOL.
grangies,
Nov 6, 12:31am
Give me a bit of sanding sink back, compared to a fry up, any day. LOL.
brad166,
Nov 6, 1:01am
PPG Scan sealer or glasurit transparant sealer seem to work ok. But I know you are PPG haters so will find something to moan about with scan sealer
grangies,
Nov 6, 1:29am
Those sealers are very, very good for inside new panels etc, or on a quick flick over of an average shitter in a wet on wet application.
The only problem is they cant be sanded.
I think gunhand is looking for an actual 2pot barrier coat to fill and seal old paintwork.
gunhand,
Nov 6, 1:31am
YEP, one that actually may stop the sinkback.
attitudedesignz,
Nov 6, 1:45am
Protec / Fortec product called Epotec (2 pack epoxy) or another good Protec / Fortec product is Parafill.
bellky,
Nov 6, 1:47am
agree. longer left at every stage the better
grangies,
Nov 6, 2:51am
x1
We just painted our pool with Epotec.
Good stuff as it self primes straight over the bare concrete.
Not cheap though. Cost us $1200 at trade price.
lookoutas,
Nov 6, 3:44am
And I always thought it was what painters did just to piss panelbeaters off. Have often wondered what those Overhaulin vehicles look like after a few months! Time is the best cure. I painted a Mk1 Z years ago and it had years of brushed-on primer over primer. Looked like a lolly-pop after I blocked it down, and the only sink-back was the fresh join where I'djust fitted a new door skin.
rob_man,
Nov 6, 5:14am
2 pack primer doesn't do you any favours when painting over Dulon. The lacquer absorbs the solvents in a way that 2 pack materials don't and swells. The 2 pack primer cures within hours and traps the solvents in the material underneath, they are never released until the primer is sanded away from the edges. You're better off to use 1K primer in those circumstances and give it time to dry properly.
grangies,
Nov 6, 6:18am
That's all very well, if lacquer is going back on top.
But if it is 2k then the sink back will be even worse. Especially if it is basecoat/2k clearcoat.
The solvent content in the basecoat bites the living shit out of lacquer primer and is not really seen until the 2k clear has gone on and cured.
richard198,
Nov 6, 6:26am
I remember when Dulon was all the rage! What happened with it!
rob_man,
Nov 6, 7:34am
I use the 1K Premium primer under Basecoat and 2 pack all the time, it works just fine.
gammelvind,
Nov 6, 8:00am
Still available, but lost favour to newer more versatile finishes, with a much wider range of colours and hues.
fordcrzy,
Nov 6, 11:19am
totally off topic but whats a reasonably priced DA sander for the home workshop.currently have one but it doesnt have the holes in the pad and seems to clog up quickly
gammelvind,
Nov 6, 7:35pm
Air or electric! AEG make a very reasonably priced 150mm, got mine from Bunnings $300 ish. Sure a Festool is better but too many $ for homers. For the same sort of $ 3M make a very nice air DA.
lookoutas,
Nov 6, 8:17pm
If it sucks - you can buy a replacement pad with holes. We have to replace ours when the grip fails - RA Johnston.
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