I've got some summit 2k urethane high build primer that I'll be spraying onto my satellite in the next couple of weeks.

The data sheet says that the pot life is 15-20 minutes. Every other high build 2k urethane primer I've looked up online says it's an hour or more.

http://static.summitracing.com/global/im...ld%20primer.pdf

So I'm a little concerned that the stuff will be unsprayable after 15-20 minutes, which might not be enough time to get around the whole car. I plan on 2 or 3 coats.

Assuming the pot life is that short, should I plan to clean the gun out every 20 minutes? If the whole job takes 1+ hour (3 coats), should I clean the gun out during the process? Or just mix up more primer/hardener and keep going?

I've not painted with this stuff before so just trying to make sure I understand how it's supposed to go.

I would say that if the pot life is that short mix just enough for 1 coat, and then mix a fresh batch for every coat you want to do. The little bit of time that it takes to mix should not cause a problem with the gun.

It says dry time 120 mins, but spray pot life 20 mins? Seems odd to me, maybe just for compacts.

My advice is if you are not sure if you can trust the pot time.
Mix a small batch and see what happens
20 minutes is a very short pot life.
Body filler can be that slow in cold weather.

Might call Summit or Global before you ruin your gun

Summit's paint line is made by Kirker. All the tech sheets on their website shows 2k primer with a pot life of 1.5-2 hours at 70F. You will have plenty of time to do a complete. If you are really worried, reduce some with the slowest reducer you can. I've never seen anything with that short of a pot life at 70.

Well I sprayed it today. I have nothing to compare it to, but I guess it laid down OK using the Harbor Freight 94572 gun with the 1.4 tip. The sheet says 1.0-1.3, otherwise I would have tried the 1.8 tip.

I started sanding part of it already with 180 grit, and even after 3.5 hours (at around 78 degrees F), it's easy to sand. I'll pick it up again in about 1.5 days.

The pot life wasn't an issue. I was surprised how little material I used.. about 60 oz of primer/hardener for 2 coats of the car. I have a lot of primer left. I see a bunch of pinholes and sand scratches to address. My plan is to have that done, spot primed, and the car painted in a couple of weeks.

Where do you plan on having it painted?

Give even 2k primer time to cure before you start sanding{preferably days not hours}...The longer the better you don't want any sand scratches to reappear... The manufacturers info on "can be sanded within X time" is for a shop to get it out the door not for an award winning,smooth paintjob...

I'm going to paint it myself. I'm going to use Kirker single stage urethane in an off white.

Single stage is Kirker and 2 stage is Sherwin Williams

Nice! Post the results when you're done. I'd love to see the finished product.