What did I do wrong? Black epoxy primer.

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danford1

What did I do wrong?
I paint some pianos and pieces for a local piano shop.
I use SPI black epoxy primer and PPG DCC solid urethane and haven't had this problem before.
I'll list the steps I took then post a picture of the result.

I sanded old paint and Evercoat Gold body filler with 180 grit.
I mixed up black part A and B in equal parts, stirring well.
I then clean off sanded surf with SPI Waterborn Wax and Grease remover. I wiped it dry.
I stirred epoxy again as it sat for about 20 minutes at this time.
I prepped my garage for painting which took about 25 more minutes. I stirred the epoxy again.
I then got busy and didn't get to spray it for about another 1 1/2 hours. The total induction time thus far was
just over 2 hours. I stirred it again before pouring it in my gun and noticed the bottom was thick and gooey but it seemed to stir OK. I think the pot life is supposed to be about 24 hours so I figured is was OK.

I used a Diamond brand tack cloth to remove any dust that may have fallen on surface then sprayed on the epoxy. Right away I saw areas about 3" long and 2" wide where the epoxy was mottled looking.
I'm pretty sure I can sand it flat prior to painting but want to know what I did wrong?
The temp and humidity during the whole time was about 80 and 80. (Michigan summer).
Here is a picture of one of the areas.
Danford1 2014-09-05 12.43.08.jpg
 
too wet and likely too little pressure . i have had this before and it was always a wet area or i left the pressure set low after using a different gun. epoxy gets finicky when shot wet at low pressure.
 
It sanded out :)
I let it cute 3 full days then block sanded it with 400 dry and it looked fine.
I then top coated it with DCC ,
Wet sanded and buffed it. The piece came out great.

Danford1
 
Also I have stumbled while walking along and the gun has gotten too close and caused that same effect.
 
exactly as shine said!! I have found it best applied with a 1.4 tip the 1.8 on my primer gun does this to me every time with epoxy and the first coat or two does not like to be glossssssy wet or bingo moon crater city.
 
I have 1.8 primer gun and if I start putting it on heavy this happens. I learned to make sure the air pressure is not low as shine stated and just put on medium coats..
 
danford1;39708 said:
It sanded out :)
I let it cute 3 full days then block sanded it with 400 dry and it looked fine.
I then top coated it with DCC ,
Wet sanded and buffed it. The piece came out great.

Danford1
Click to expand...

Thanks for the update.
 
I get this all the time with epoxy too. Like the others have said, if you get it too heavy or wet on one spot it will do this. It's no big deal, just block it out and it will sand out fine, but you will end up sanding most of it off so you'll need to go over that area again.
 
I lost air pressure while shooting SPI Epoxy and got a heavy shot of paint in a small area. Pretty much repeated what Danford1 did. I believe it was too much paint with no pressure, or a pass too close and spray pattern out of square with the surface. I got the two coats applied, let it sit for 24 hours and block sanded it smooth. Went thru on a couple places. I want to shoot the whole thing again with another coat anyway. It will be before the 7 day window. Is 180 wet sanding the area I block sanded ok to do the recoat (doing nothing to the rest that was not sanded)?

So If I have a little sanding dust on the previous coat of epoxy, how do I clean before the next one or two coats?

- - - Updated - - -

I lost air pressure while shooting SPI Epoxy and got a heavy shot of paint in a small area. Pretty much repeated what Danford1 did. I believe it was too much paint with no pressure, or a pass too close and spray pattern out of square with the surface. I got the two coats applied, let it sit for 24 hours and block sanded it smooth. Went thru on a couple places. I want to shoot the whole thing again with another coat anyway. It will be before the 7 day window. Is 180 wet sanding the area I block sanded ok to do the recoat (doing nothing to the rest that was not sanded)?

So If I have a little sanding dust on the previous coat of epoxy, how do I clean before the next one or two coats?
 
The 180 spot should be fine as well as the rest inside the 7 days, I always go ahead and hit epoxy with a red scotchbrite after 24 hours just because it doesn't take but a couple minutes and its cheap insurance, also when I work on an area I pretty much always just go ahead and take the wax and grease remover to it, once again cheap insurance, I'd rather take 10 minutes scuffing and wiping than have some problem down the road because I got scatterbrained and missed my recoat window or had my dirty hands, or one of my little demons dirty hands touch something I had forgotten about.
 
45 lbs when trigger is pulled works good for me, but Im far from experienced.
 
That is probably another thing I did wrong when this happened. I had the gun (old style gravity fed Devilbiss) pressure about 30 psi with trigger pulled so I wouldn't have as much mist floating around in the air. I didn't have any exhaust fans on...
I now know I did a few things wrong and will learn from my mistakes. I have another piano coming tomorrow.
I'll be squirting more black epoxy later this week :)
Danford1

- - - Updated - - -

That is probably another thing I did wrong when this happened. I had the gun (old style gravity fed Devilbiss) pressure about 30 psi with trigger pulled so I wouldn't have as much mist floating around in the air. I didn't have any exhaust fans on...
I now know I did a few things wrong and will learn from my mistakes. I have another piano coming tomorrow.
I'll be squirting more black epoxy later this week :)
Danford1
 
Shine, I obviously spoke too soon when I posted 45 pounds, Ill try 35. I didnt want to mislead anyone so I deleted that post. Thanks for correcting me. I have to be a little more careful about sharing my experience when I have so little.
 
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