Time Between Coats
 

When Ive done DIY paint in the past, I have always just followed the TDS of the product. Which for urethane products like I am using, will usually say 15ish minutes flash time in between coats of Single Stage or Clear.

Ive been lurking on the SPI (Southern Polyurethanes Inc) forums. Both the forum users and a tech guide on the page often recommend much longer flash times between coats. Including letting an epoxy seal coat sit at least 6 hours or even better overnight before applying the color. And the same with letting it sit for longer before applying the clear.

The talking point that I have seen is that the directions in the TDS are usually geared towards shops where time is money, so they are giving you the minimum time required for flash etc. But for the hobbyist where you arent losing overhead for every minute that passes there is a benefit to longer times between coats. They are especially adamant about letting the epoxy sealer sit for longer.

To me, the only big benefit for someone like myself painting outside of a real paint booth, is if I let it sit longer I can then tack rag between coats more safely to reduce dust contamination.

What say you guys?

Snips from the SPI "Perfect Paint Job Tech" https://www.southernpolyurethanes.co...ect-paint-job/

When all the primer blocking, and any necessary primer repairs are finished it is always best to use the epoxy as a sealer. Mix up enough epoxy to go around the car with one wet coat and adding a double shot glass of SPI 885 Urethane Reducer per quart. Let the epoxy sit for 30 minutes. Stir one more time and strain. Spray one full wet coat of epoxy over the entire car. The epoxy should sit for 6 hours before spraying basecoat, the best option is let it sit overnight.

It’s very important to use the slowest urethane reducer in your basecoat that you can get away with regardless of outside temperature. Even if you spray at 70- 75 degrees, use slow reducer in the base. Just allow enough extra time for the basecoat to flash off and dry. The difference between a slow grade and medium grade reducer will show up in the final gloss.

Spray the first coat and let it totally dry before spraying the second coat. It is best to wait 30-45 minutes between coats of base. Always wait 45 minutes between base colors that contain a lot of black pigment.

Random supplemental question.

How to I keep a wet edge in the middle of the station wagon roof? On the sides I can walk the side of the car, but with the middle of the roof where I have to use a stand then get down and move the step ladder how should I go about that?

The time to wait after applying the SPI epoxy, before the base coat depends upon how much you reduce it.
https://www.spiuserforum.com/index.p...-sealer.10040/

As far as using SPI epoxy as a sealer I usually mix 1:1:1 which is 50% reducer (8oz epoxy:8 oz activator:8 oz reducer)and can put down base in about an hour or so after depending on temperature.
The “perfect paint job” suggests 2 shot glasses of reducer (3 ounces) per quart of epoxy that was mixed at 1:1. A quart of epoxy mixed has 16 oz epoxy and 16 oz activator so adding the 2 shots (3 oz) is roughly a 10% reduction. That ratio would take longer to be ready for color so it’s suggested to wait 6 hours or if you can wait let it wait overnight.
If you’re on the SPI forum questions are best asked there as there are helpful people who have been using SPI products for years more than myself.

Im sorry I should have specified, Im using Kirker epoxy which doesn't suggest more than a 20% reduction in the TDS. SPI just has active forums and it was making me think.

If I were using SPI products, I would have just asked there.

The Enduro Prime Im using says up to 20%, which is what I'm planning on, and waiting 30 minutes. BUT as with the SPI epoxy, you see the answers all over the place, in that thread linked, dude says 2-6 hours. And Ive seen several other threads say overnight is even better.

My primer says 30 minutes to topcoat, but can be topcoated without sanding for the next 5 days.

Honestly, I think Im going to do the epoxy, let it sit, come out and tack it in the morning. Then do coats of color and clear with 45-an hour in between the next day. Longer than the min flash time on the recoating, but it should be a little more dry which means I can tack it between coats with a little less worry I think.

Caveat to this would be if I only look like Im going to get one day of agreeable weather. Then Ill just rumble through it all.

Be very careful about your re-coat time with your clear. I would not wait beyond 20 minutes with your last coat. Waiting too long for the last coat can lead to major solvent popping. And if you're thinking about tacking between coats of clear, forget it.

Copy that

I thought solvent pop was from rushing coats and trapping the outgas?

It’s done.

It went……medium. Car is 1 color now which is good. No matter how much you clean and try to make your garage into a paint booth it still gets dirt and trash in it. So it’s not perfect. But the car is far from perfect. I really don’t want to wet sand so I’m probably just going to live with it. I might throw a polish compound in it and see what that removes.

I’ll do a more detailed write up in a separate thread later with lessons learned and the like.

In brief, I was right to be afraid of that long roof. It was really hard to keep an even overlap on that roof and hood being from the “wide track” era. I just wasn’t tall enough. So with the metallic paint I do have some tiger striping. In those areas. Sides of the car are fine. Metallic single stage is def harder to spray than solid color.

The other huge bummer was In my last coat of single stage on the roof I got some drips in the hood. One bad one and several smaller ones. I honestly don’t know what happened. Which bothered me even more. I think I just overfilled the cup and it dripped out the vent. I only sprayed 1 stage of clear after because if I try to fix it I didn’t want to have to razor blade off multiple coats of clear like I had intended to lay down. You gotta be pretty close to see them but still it bothers me.

Typo earlier. The drips are only on the roof. But the hood has the worse stripe. I think I’m going to scuff and repaint the hood at some point. Just pop it off and prop it up so I can paint it standing in front of it.

Good job on the Paint job.
Painting a Car is a HUGE accomplishment.
All of us that have painted our cars can see the flaws in them, others rarely notice or comment. And, Paint can always be repaired.
I say, Pat yourself on the back, Have a beer and enjoy your new car.
Congrats, Your wagon is very cool.

Thank you. I’m def going to repaint the hood, and I’ll eventually find some time for some low level wet sanding and buffing. Probably just 2000>3000 trixact then a two stage buff.

It looks better with all the trim back on it.