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Old 06-25-2005, 04:52 PM
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Got solvent-pop. What to do now?

I painted my 69 Vette with PPG Global DG single stage (Daytona yellow) and I have a problem I need some advice on. This is the 3rd time I have painted with SS acrylic urethane but the first time to use the Global and the first time I've had this problem. I know it is my fault for not following instructions, but I've done it the same way before and gotten away with it.

The product sheet said to put on 2 coats or to hiding. Since I was intending to sand it and buff, I decided to put 4 coats on. Well, I got some solvent pop. I also did fairly heavy coats and that probably exacerbated the problem. It's not everywhere but it came up where I put it on the heaviest. It took about 15 - 30 minutes after I stopped painting before I noticed that they were showing up.

At first I didn't think it would be a problem because I figured it would smooth out when I color sanded.

Today, I started to color sand the car. When I inspect the sanded areas and get my eyes down close to the paint, I can see tiny (and I mean very tiny) pin-holes in the areas where the solvent pop took place.

OK, what to do now?
I have plenty of paint left over. I figure I'll sand the whole car with 400 or 500 and shoot it again. Will these pin-holes fill with the new coat? After shooting it again do I need to make sure I don't color sand thru the new coat to the originally laid down paint. Should I put one new coat on or two?

Now, this leads to another question. I wasn't able to lay down the paint without some orange peel. I would like to get the next coat or coats down as smooth as possible so I don't have to do much color sanding.

I used a cheapo Harbor Freight 43430 gun (gravity feed, 1.4 tip). However, it is one that people on this forum have had good luck with. Should I buy a better gun? If so, can you recommend the best one for the SS paint?

I'll appreciate all advice.

Roger

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Old 06-25-2005, 05:46 PM
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What reducer were you using D870? probably D871?
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Old 06-25-2005, 05:48 PM
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What temperature are you spraying in and how much humidity?
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Old 06-25-2005, 05:51 PM
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4 coats (wet) of Global, thats a lot of paint!

I would wetsand with 600 until all the holes are gone, than sand with 1500 and maybe even finer again and buff.
I would do this because of the amount of paint you have on the car.

If you sand and repaint you still must get the pinholes out or down the road they will soak up.

If you do recoat I would use slow or very slow and only spray one coat to prevent more popping from coming up as can happen very easily if you spray two coats unless you spray back to back with out letting the first coat flash.
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Old 06-25-2005, 05:52 PM
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Quote:
Originally Posted by baddbob
What reducer were you using D870? probably D871?
I'm using D872. It's hot in Austin this time of year so I went with that. It's says it's for 77 to 95 deg. and it's somewhere in the mid 80's in my garage.

Roger
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Old 06-25-2005, 05:57 PM
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Quote:
Originally Posted by baddbob
What temperature are you spraying in and how much humidity?
It's always in the 90's outside and I have 2 big fans for cross ventilating. The humidity is usually in the upper 30's in the afternoon. However, the day I shot the car it was probably in the 40's or maybe 50.
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Old 06-25-2005, 06:00 PM
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D872 is what I was going to suggest, I've never seen pop with 872. You must have a lot of paint on there. If you sand it down with 600 then step it out to 1500 or finer like Barry suggested it would buff out OK if there's enough material left on the car, I bet it'll be alright. Did the first 2 coats go on smooth or were there texture problems on every coat? Do you have good airflow-is there much of a cloud in your spray area after you apply a coat?
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Old 06-25-2005, 06:20 PM
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Quote:
Originally Posted by BarryK
4 coats (wet) of Global, thats a lot of paint!

I would wetsand with 600 until all the holes are gone, than sand with 1500 and maybe even finer again and buff.
I would do this because of the amount of paint you have on the car.

If you sand and repaint you still must get the pinholes out or down the road they will soak up.

If you do recoat I would use slow or very slow and only spray one coat to prevent more popping from coming up as can happen very easily if you spray two coats unless you spray back to back with out letting the first coat flash.
Thanks, Barry.

In the areas where the pop was the worst I have already sanded quite a bit and the pin holes are still there. I haven't sanded through yet but I'm almost sure that I will if I try to get all the pin holes all the way out. I am also afraid that even if I don't sand through, it may get real thin and I may buff through it afterwards.
I think I would feel better to take your second option and sand all the pin holes out and then re-coat.

Yes, I put a lot of paint on the car and that was my intention as I didn't want to sand or buff through. The only thing now is that now I will not really know how many mils I'll have on the car total. But, I will be removing a significant amount when I sand. I figure I'll use my long board with 320 dry and then go over it with 400 or 500 wet before re-shooting.

Btw, what so you mean by soak up?
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Old 06-25-2005, 06:31 PM
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Quote:
Originally Posted by baddbob
D872 is what I was going to suggest, I've never seen pop with 872. You must have a lot of paint on there. If you sand it down with 600 then step it out to 1500 or finer like Barry suggested it would buff out OK if there's enough material left on the car, I bet it'll be alright. Did the first 2 coats go on smooth or were there texture problems on every coat? Do you have good airflow-is there much of a cloud in your spray area after you apply a coat?
I would say that even my first coats weren't that smooth (not horrible though). However, I am not that good at adjusting guns or with spraying technique. That's why I am not sure whether I need a better gun or just need to learn to adjust and spray better or both. I've read Barry's "How to adjust a gun" post but I still feel like I'm just guessing.
Yes, I have good airflow. Those 2 big fans are blowing the air out and I have furnace filters mounted in the doorway on the other side of the room.
There is not much of a cloud, it clears off pretty fast.
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Old 06-25-2005, 06:33 PM
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Roger, you'd be fine prepping with 400 then 600 before paint. I think what Barry meant is if you did repaint without sanding out the holes and the paint flowed over they would eventually show when the cure is done and it shrinks down.
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Old 06-25-2005, 06:52 PM
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Quote:
Originally Posted by baddbob
Roger, you'd be fine prepping with 400 then 600 before paint. I think what Barry meant is if you did repaint without sanding out the holes and the paint flowed over they would eventually show when the cure is done and it shrinks down.
I guess my question here is do I have to sand enough to get every trace of the holes out? After I sanded what I thought was a lot, I can still see traces of holes. However, I have to get my eyes about 3 inches from the surface to even begin to see them. If I use a magnifier, I can see them but they are very very small.

I really do want to re-coat. If I know there are pin holes, it will bug me, even if nobody else sees them.

I used my long board a little already with the 320 dry and it works real well.
I'll finish prepping with 600 like you say.
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Old 06-26-2005, 03:48 PM
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Quote:
Originally Posted by baddbob
D872 is what I was going to suggest, I've never seen pop with 872.
After thinking about this, it seems more logical that a fast reducer would flash faster and would be less apt to cause solvent pop after following coats. I know this must be incorrect, but maybe you can explain it?

Update:
I've been doing more sanding today but I don't seem to be able to get to the bottom of the pin holes. I really wanted to take Barry's/Bob's 1st choice advice and not do a re-coat, but I think I would just have to sand too much.

I will probably do some testing before I do the re-coat to try to spray as smooth as possible even though I still intend to color-sand and buff the final finish.

I may try my old Binks 2001 siphon versus that Harbor Freight gravity gun. I always had good luck with the Binks but maybe I just don't now how to adjust the gravity gun.

Roger
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Old 06-26-2005, 08:09 PM
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i have had this problem also years ago, ill tell you from experience, if you dont get them out and do have to repaint , they will show, my advice would be to sand with 400 wet paper completely until there gone then 600 wet paper and repaint, even though it may sound crazy, i find it to be alot easier.
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Old 06-26-2005, 08:43 PM
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The holes may have been in the primer, I've seen this happen when primer was applied really thick and skinned over fast, usually guidecoat will show any though when the sanding was done.

Your thoughts of a fast reducer working better because it evaporates faster sounds logical but actually doesn't work and leads to more trapped solvents-pop. The slower reducer will keep the surface open longer for more solvents to get released. Took me quite awhile to grasp this theory but I've proven it to myself many times. The clear actually dries faster in the long run with slow reducer because less solvents are trapped. Up untill about four years ago I always thought fast reducers made the paint cure faster- I was wrong Not that you can't get by with fast reducers but you open the door for solvent pop, slow dry times, cloudiness, and dieback. Temperature also factors in,55- 60 degrees D870 might be perfect for a complete paint. Bob
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Old 06-27-2005, 04:55 AM
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Quote:
Originally Posted by roger1
Those 2 big fans are blowing the air out and I have furnace filters mounted in the doorway on the other side of the room.
There is not much of a cloud, it clears off pretty fast.

Pulling air across your painted surface increases your solvent pop
chances, the top may be "Skimming" over before the solvents are
evaporating. Use a slower reducer and wait longer between recoats.
If I have airflow I use the slowest reducer I can find,when it's hot
I may add a little retarder as well, I have to wait a long time for
it to flash but it flows beautifully.
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