2K Clear Coat

[Jackyl]

Did a search on automotive clear and 2K clear, each thread touched on the issue that I am seeing, but not 100% sure I got the answer. I have used this paint before, mainly for gas tanks over a color, but I figured I would give it a try over wood. It looks fantastic, nice mirror shine on it I am completely satisfied with the sanding and polishing.

Problem was the other night I placed the hardware on the top to take some pictures of it to get an idea of how it was going to look. To my surprise I got outlines of the hardware, not huge outlines, small hairline corners on the one and an arc on another appeared overnight. My concern is that the area is still soft after a week which to me is unusual, the only thought I had was that I machine polished it prior to putting the hardware on, would this have softened it at all? If it was completely outlining the parts I would be furious, but the small 2-3mm outlines will just be covered when I screw everything down.

My thought was to put it out in the sun for the next 2 days and let it sit not attempting to put the hardware on, but my gut is telling me that it should be hard.

Thoughts?

[bob123]

I've been dabbling with 2k clears lately, and my favorite part is how it cures fast. If yours is still "tacky" or "gummy" I would be willing to guess you may have not mixed it properly? That or there was an inclusion (moisture, or otherwise)?

If it does wind up curing properly, those lines should disappear when you cut and buff.

[killemall8]

How long did you let it dry for? And what did you spray it over?

I have used a lot of 2k clears, and they can be finicky in certain situations.

1, they dont dry correctly directly on wood or over some wood sealers.

2, they usually have to dry a lot longer than the can says. "dry" is not the same as CURED.

[rhoads56]

1. wrong

2. wrong

If you follow the instructions to the letter, within the parameters of the product, it will do exactly as it says.

Ive sprayed final coats less than 24 hours before assembly and buffing, and then putting it in a case, to freeze in a cargo hold of a 22 hour flight.

If you are heating the paint to assist in curing, you need to let it gas off first. It it skins off the solvents cant escape, and it will remain soft.... forever. I allow 4-5 minutes for gas off, then hit it with heat lamps.

[bob123]

How long did you let it dry for? And what did you spray it over?

I have used a lot of 2k clears, and they can be finicky in certain situations.

1, they dont dry correctly directly on wood or over some wood sealers.

2, they usually have to dry a lot longer than the can says. "dry" is not the same as CURED.

I have some stuff that I can wetsand and buff in about 30 minutes lol. 2k CURES by catalyst, it shouldn't require a lot of time to "cure" vs "dry". I let my stuff dry overnight just to be "safe" but it's not needed. I also haven't had any issue over pretty much anything I've done wood wise. Bare wood, colored wood, painted wood, sealed wood... all the same for me.

[killemall8]

1. wrong

2. wrong

If you follow the instructions to the letter, within the parameters of the product, it will do exactly as it says.

Ive sprayed final coats less than 24 hours before assembly and buffing, and then putting it in a case, to freeze in a cargo hold of a 22 hour flight.

If you are heating the paint to assist in curing, you need to let it gas off first. It it skins off the solvents cant escape, and it will remain soft.... forever. I allow 4-5 minutes for gas off, then hit it with heat lamps.

That is why your experiences are different... because you are using heat lamps... Without them it doenst dry like that naturally.

I have mixed it exactly and sprayed it exactly as directions say... and it never dried on wood sealer. But dried fine on paint. Speaking from personal experience, not opinion...

And obviously depends on brand and quality... lower qualites are just not the same, as i have found.

[demonx]

There's a difference between touch dry, assembly dry and fully cured.

Automotive 2k takes MONTHS to fully cure. That's what sink back is if you don't grain fill properly.

Perry did mention something that is usually the case where most people screw up - it has to be done properly. People think. "Oh its just paint" and do whatever, but 2k is a product that relies on chemical reaction and must be treated as such

I only use heat lamps in colder months. I like a longer natural cure. I also like to not cut/polish or assemble until its hung for a week or longer and hardened right up.

My guess is you've sprayed too thick. Its skinned off, underneath isn't cured.

[demonx]

Also, not all products are created equal.

I covered a guitar about two months ago with a sealer. I put it on twice as thick as I normally would.

There are solvent pops (popped blisters) everywhere and spots where even now, months later the stuff isn't cured. Normally if I lay it on thin I can sand a few days later. Long story short, I've experimented, the stuff doesn't like thick and now one day when I get the chance it all gas to come off and start again.

[rhoads56]

1. wrong

2. wrong

If you follow the instructions to the letter, within the parameters of the product, it will do exactly as it says.

Ive sprayed final coats less than 24 hours before assembly and buffing, and then putting it in a case, to freeze in a cargo hold of a 22 hour flight.

If you are heating the paint to assist in curing, you need to let it gas off first. It it skins off the solvents cant escape, and it will remain soft.... forever. I allow 4-5 minutes for gas off, then hit it with heat lamps.

That is why your experiences are different... because you are using heat lamps... Without them it doenst dry like that naturally.

I have mixed it exactly and sprayed it exactly as directions say... and it never dried on wood sealer. But dried fine on paint. Speaking from personal experience, not opinion...

And obviously depends on brand and quality... lower qualites are just not the same, as i have found.

Dont assume I always use lamps. I simply added that bit in case you were...

[demonx]

I would have instantly assumed since rhoads58 is in Perth he has no need for lamps!

I also would assume from watching a video of him spraying years ago that the products we both use are so different that our advice is going to differ.

For example, Rhoads58 posted a video a year or two ago of him spraying a body, if I had have sprayed that much in one pass using the products I use then it'd all run off like a river onto the floor in a big puddle.

What I'm getting at, just because someone says 2k auto doesn't me a its all the same. When I switched brands of clear a year ago I had to learn how to spray it, the way it sprayed, the thickness it wanted, the curing times, its reaction to heat lamps and everything else was very different to the other brand I'd been using for years.

It all comes down to experience , knowledge and following instructions and knowing when to deviate from them and why

[demonx]

An example of knowing when not to follow the instructions: several years ago I was spraying an old Chevy and was using a pre primer product I'd bever used before, I experienced some trouble.

I had the company technician come to my workshop and to a range of tests to see if the result was my doing or a faulty product.

Turns out it was a very fussy product and I'd sprayed it too thick. However I thought I'd sprayed it exact to the data sheet.

The companies technician, the guy sent out from their laboratory told me don't pay any attention to the tech sheet. The product I was spraying needed twice the maximum flash time lusted on the sheet and as soon as I allowed a 48hr buffer time rather than the companies recommended 24 hr, I never had any problems.

Knowledge. Experience. All comes from trial, error and failure

[killemall8]

I would have instantly assumed since rhoads58 is in Perth he has no need for lamps!

I also would assume from watching a video of him spraying years ago that the products we both use are so different that our advice is going to differ.

For example, Rhoads58 posted a video a year or two ago of him spraying a body, if I had have sprayed that much in one pass using the products I use then it'd all run off like a river onto the floor in a big puddle.

What I'm getting at, just because someone says 2k auto doesn't me a its all the same. When I switched brands of clear a year ago I had to learn how to spray it, the way it sprayed, the thickness it wanted, the curing times, its reaction to heat lamps and everything else was very different to the other brand I'd been using for years.

It all comes down to experience , knowledge and following instructions and knowing when to deviate from them and why

I completely agree. Every 2k clear i have used was completely different. 1 i used had the most amazing spraying qualities, and the best gloss ever. But it never dried fully hard.

I tried a different brand, it dried hard and fast, even in the garage in mid winter. But it was really hard to work with.

[sunday_luthier]

I recently had issues spraying automotive clear which never dried, stayed soft for months, and I got tiny white dots in the finish which I will eventually start over. Turns out I didn't have a moisture trap in my spraying setup (a big no-no that was probably the reason I got those dots). Anyway, I went to my local car supply store to buy some clear and explained to he guy my problem with curing time.

Turns out that when they sell you automotive lacquer, they assume you are going to spray it in an spraying oven. I have to specify "fast curing" to get stuff that dries in a decent amount of time. I'm refinishing a Strat body right now and it seems like a big difference from what I had before... i hope it turns out good. Though I suspect I'm still spraying too thick...

[demonx]

I have two moisture traps before the air gets to my gun

White spots can also be overspray landing back onto the surface. Found be contamination. Could be dust.

The not curing could be unmixed product. Most people don't know how to mix and think stirring a bit is mixed, it's not. It could be spraying in the wrong temp. There are different temp range additives. It all matters.

I've talked about stirring before many times. 200 stirs is a good number. Twenty times left, twenty times right and so on. If you just stir and stir the mix just spins around rather than mix together. Most products 100 times isn't enough. 200 is a safe number

[Jackyl]

The surface did dry to the point where I wet sanded it back to a fine polish. The issue which strangely fixed itself this weekend, was the indentation of the parts into the clear coat. I ended up covering the guitar this weekend on my work bench since I had to move on to building a door and a book case, last night I was able to take a quick look and found the spots completely gone.

The first spray for the guitar was over a month ago and like in the last few posts I learned my lesson on using the medium hardener. It ended up drying too slow and causing the pin holes in the clear. As soon as I saw the pin holes I knew it was going to require a re-spray and I switched back up to the fast hardener which this actually was. I sanded down the surface to just above the wood leaving the base coat there for a week and half in my garage hanging. Then sprayed the guitar and left it for another week hanging in the garage where the temp during the day gets to 90 Degrees easily.

Then I removed the guitar and started wet sanding with fantastic results this time around. Interestingly enough the painter that I consulted about the pin holes actually felt it was from the wood releasing trapped air, especially since it was not over all the wood types just the walnut. In addition I also run two dryers in my system since I found out the hard way when I started spraying cars and gas tanks.

Do to time constraints, I probably will put the remainder of the hardware on tomorrow. Having sprayed it over 2 weeks ago I have to assume that it is hard enough to assemble and I cannot wait any longer since it needs to be in the mail tomorrow. Which I know I will not get it out until Wed at the earliest.

Thanks for your inputs.

[kench]

I agree on stirring. Think like this: each resin molecule should mate with a catalyzer molecule (this may not be scientifically accurate, but the principle is true). And that takes a lot of stirring. And use something that is wider than a stick to stir (I use a dinner knife).

[bob123]

Also, make sure you guys filter your paints.

Not sure if its needed, but i double pour the paint. Anyone have thoughts on that?

[demonx]

Then I removed the guitar and started wet sanding with fantastic results this time around. Interestingly enough the painter that I consulted about the pin holes actually felt it was from the wood releasing trapped air, especially since it was not over all the wood types just the walnut. In addition I also run two dryers in my system since I found out the hard way when I started spraying cars and gas tanks.

The "pin holes" are either escaping air as suggested or solvent pops. If it's escaping air it means you haven't grain filled properly. If it's solvent pops then it means you're probably spraying too thick, too slow or too many coats in one session, all three things = paint too thick.

As discussed earlier if heat is used you can get solvent pops, because you've changed the curing atmosphere which then means the surface dries much faster and the solvents underneath are trying to escape as theyre still trying to cure under a hardening surface. Thinner is better in this case.

I only use fast or very fast hardener or reducer in primers. All colors or clears I use a medium. You need to understand how this effects YOUR local environment and not just copy what someone on the internet says though, however the only time I would imagine using a fast or very fast additive would be in freezing cold winter, yet I just use heat lamps (not on all the time, only on for short period towards end of spraying and short time after) and still use the medium.

I've had in Wenge (very large open grain) this escaping air thing during an epoxy grain filling procedure and I think it was because I did it too thick. A combination of both problems.

[bob123]

All this serious discussion makes me feel very fortunate with my catalyzed experiences... I haven't had any issues since following demonx's stirring techniques, double pouring, and filtering.

Curious, you are mixing in glass, not plastic right? (just dummy checking)

[rhoads56]

Mix in plastic.

When Ive had tiny white dots in the clear, it was from the solvents not being able to escape prior to the surface skinning over.

Could have been moisture too, but thats the reason they gave me. It stopped when I used less reducer, and removed heat sources.

I use poly or acrylic urethane, 5% reducer max, fast hardner, and the additive hardner booster, and a couple drops of silicone retarder. I spray a mist, then heavy coat. If it doesnt look like its about to all run off, I didnt put enough on. I'll often hang the guitar for a couple minutes, then flip it and hang it from the jack.

320 or 400 for each sand between coats, 400 before final coat.

Then 1500grit foam pad, then 3000/4000 grit foam pad. Then buff with lambswool.

[bob123]

O.o what plastic cups are you using? lol Every time I've tried plastic, it just eats right through the stuff... glass always works well for me. I blanked out and used a plastic cup the other day, made a huge mess haha.

[killemall8]

You have to use mixing cups made for mixing paint... You can get them anywhere you buy your paint. They are solvent proof.

[demonx]

The mixing cups they sell at the place you bought the paint from. They'll be solvent proof and cheap enough you buy them but the stack, throw them out after each use.

I tend to swirl thinner in them if I haven't used hardner and give them a wipe out and re use them for collecting/ mixing dust etc for inlays and things too

[bob123]

O.o

Here i am cleaning my glasses out for no reason lol. Good to know, ill grab some.