Test Spray Issue

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Test Spray Issue

Post by NAP1947 on July 22nd 2011, 9:04 am

I have got the first door for our MG painted with a couple of coats.
I have been using an HVLP gun and custom mixed Tremclad mixed 2 parts paint to 1 part thinner with .25 part hardener.
The first coat was great smooth, shiny and hard (did take 24 hours to really feel hard)
The second coat has a fine sandpaper like grain to it. I know I have done something wrong but am not sure what.
The first coat had very little overspray paint in the air compared to the second coat, I am wondering if this is indicative of a problem.
The air goes through a dryer, filter and pressure regulator adjusted to 50lbs of pressure.
I adjusted the gun to an oval pattern with what looked to be even coverage on a test wall.
Can anyone suggest what I need to consider before I sand and respray?
Want to have some idea of what I am doing before I tackle the whole car.
Thanks and cheers
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Re: Test Spray Issue

Post by rick howe on July 22nd 2011, 11:59 am

cheers Hi Nap i to am new to this site and just put my last coat on my triumph; i rolled the paint and i have to say it went down great i thought about spraying but with no garage here and i didn't want overspray in the air; i chose to roll it i have to say if your in the 1st stage i would put down the gun and pick up a roller. My rolling took about 2 weeks of mornings to put down 8 coats ;i got lucky the weather stayed sunny and no humid air to ruin the paint; humid air will make the paint look grainy when spraying or rolling only paint early in the day if your outside ; good luck and if you can post pictures let know how i can't get any pictures to show.
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Re: Test Spray Issue

Post by NAP1947 on July 22nd 2011, 12:16 pm

Thanks Rick, it has been very humid here perhaps that is the problem.
I will get the panel ready and spray when humidity is down, if that does not work I will think about the roller.
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Re: Test Spray Issue

Post by cac1967 on July 22nd 2011, 6:36 pm

I think your problem was you waited too long between coats, if the first coat was completly dry, your thinner in the later coat's was lifting the paint underneath , the best process is first coat as a light tack coat, wait about 20 minute's, second coat is a little heavier or call it your color coat,wait another 20 minute's and apply your third coat or your shine coat.I think it was the thinner lifting your previous coat's ,let it dry about 3-5 day's sand with 320-400 and recoat, hope this may help.
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Re: Test Spray Issue

Post by NAP1947 on July 22nd 2011, 6:53 pm

Thanks, I will do that.
Do I really need hardener with this paint?
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Re: Test Spray Issue

Post by cac1967 on July 22nd 2011, 7:03 pm

The hardner makes the paint harden quicker, I've sprayed rustoleum on the door jambs on my 87 ranger, I used 8oz paint, 4 oz acetone, 4oz mineral spirit's , flowed great, shine is awesome, but took a while for it to completely harden , could press it with my finger for about 6 day's so I would use some hardner.
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Re: Test Spray Issue

Post by NAP1947 on July 22nd 2011, 7:23 pm

I have been using hardener, was one of my questions to myself when I was trying to figure what I was doing wrongs.
Thanks again.
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Re: Test Spray Issue

Post by 63Falconconvert on July 23rd 2011, 7:55 am

Question, where is your regulator located? You want 50 psi AT the gun. Remember your pressure will drop from your tank to the gun. If your reading 50 at the compressor you may be only getting 35 to 40 at the gun.
Another question is how large is your compressor.
Check this out, it may be of some help:
http://www.stovebolt.com/techtips/hvlp_paintgun_basics.htm
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Re: Test Spray Issue

Post by NAP1947 on July 23rd 2011, 8:03 am

My pressure regulator is at the end of the dryer filter setup. There is a 15 foot hose between it and the gun. My gun specs 40 to 50 input so I figure I am OK.
I am running a 2.5 hp compressor with a 20 gal tank plus close to 100 feet of 3/4 air line between the tank and the dryer filter setup.

The site was most informative.

Thanks
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