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MG Midget and Sprite Technical - Paint curing

Will 2K paint air dry without its hardener, albeit much more slowly?

Reason: can I decant a few Cc's of the 2K paint used to spray my car into an air tight bottle for occasional use for touching up stone chips etc with an artist's brush. Or does it need the hardener, in which case it would need a small quantity mixed on each occasion, and any not then used would be wasted.
GuyW

I have used unhardened 2k for touching up for the last few years. Seems to work ok
Bob Beaumont

My brother, who was a paintsprayer when younger, says 2k will air dry. I presume it's not as tough without the hardener, maybe more like celly. But for touch in, I'd use it without hardener.
Bill Bretherton

Thanks both. On that basis, I think I will give it a try.
GuyW

Two pack P/U requires the isocyanate in the curing agent to cross link with the paint to cure, it may well appear to dry but it will not fully cure to a fully hard finish, for stone chips there would be no harm trying but I would not be surprised if it washed off under pressure and would be difficult to sand the touch up flat.

Tim Lynam

Guy
If you have hardener, I suppose you could add a few drops to the small touch up paint quantity in a cleaned yoghurt pot or something similar. Maybe use a turkey baster, one for the paint and one for the hardener. Or just dip throwaway brush in hardener and add to paint.
Bill Bretherton

All do-able, Bill. I was just looking for the simplest system!
Timmy has answered it. I wasn't sure if the hardener was a catalyst, or part of the actual bonding agent as he describes.
Had it been a catalyst, my understanding of a catalyst is that it speeds up a reaction, suggesting (in this case) that the hardening process would eventually take place, only slower. Timmy suggests that without the hardener, it would never really set.
GuyW

It's possible the paint may cross link on its own without the hardener although slowly. Styrene is good for that and why it has a shelf life.
David Billington

I've been googling trying to find out what those small touch up bottles you can get contain - I presume it's acrylic paint and an air/temperature based hardener. If you know your paint code any colour can be matched AIUI.

We had our V40's stone chips and minor scratches repaired by one of those "chips away" companies a couple of years ago. The guy turned up in December on a wet day and put up a gazebo. I was very skeptical but he did a superb job. He used heaters to set the paint (sprayed with small gun via compressor). He gave me a small container of the paint he'd mixed up so it must contain a hardening agent, I presume. I may have asked what the paint was but can't remember now.
Bill Bretherton

I have to say my touch ups using just the paint have been fine. I have not noticed any problems with it drying.Indeed I found the original 2k paint that had been used had gone hard in the tin! I had to buy some touch up recently. It was painted in 2010 though!!!!
Bob Beaumont

I'd be inclined to get a couple of ear pipettes, one for colour and one for hardener and drip bit of each onto an old chinese takeway lid to mix as close to the correct ratio as I could guess.

Or, your original paint supplier may be able to mix up a touch-up kit from the paint code.

P Peters

Yes, that would be another smart way.
I was looking for a simple, repetitive solution and assumed there was a recognised and normally adopted solution. I suspect it actually involves using a different air drying paint - acrylic, as Bill says. But I have around 2 litres of the original 2k left over!

To fill even tiny stone chips correctly actually takes several applications, building the paint within the chipped area until it is proud of the adjacent surface before flatting back and polishing. Mixing in a hardener for individual droplets of paint, then having to repeat for several layers verges on more than my attention span cane cope with!

GuyW

2k paint without hardener will just take longer to harden. I have used it on my car several times on stone chips. Use it unthinned with a small brush and re-apply it next day to bring the level of paint up to the original. You may have to do this a couple of times. When it eventually hardens, use a small piece of 600s wet and dry on a small flat rubber or wooden block to carefully flat the paint then use Farecla G3 and a car polish to get a good finish.
I got a big stone chip right in the middle of my bonnet and got rid of it with this method.
Bernie.
b higginson

Thanks Bernie.
First application of 'pure' 2k paint sans hardener applied this morning. It seems to have gone pretty hard already but I will wait until tomorrow before a second coat.
GuyW

This thread was discussed between 13/06/2023 and 17/06/2023

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