humidity and epoxy primer
 

Are there any strict humidity limits when shooting epoxy primer. I have a window of opportunity to get some primer done but it's going to be very humid out.

Thanks

If it’s SPI call the tech line and ask Barry. Or send him a text. He will answer.

Don

I sprayed my cowl, firewall, and frame rails from the firewall forward last night. If I was lucky the humidity was only 90%. I knew I’d have a good chance of spraying in not the best conditions (humidity) so I gave it a longer induction (12+ hours) and sprayed straight with no reducers. I think dragging reducers into the mix only complicates things with high humidity.

The biggest issue I could see is if you’re shooting it as an only/top coat in a visible area, doing it in bits and pieces, and the humidity is all over the place each time you shoot a piece. Your finished gloss/sheen levels on all the finished parts might not match.

BTW that was regarding SPI primer. I’d hate to see someone induce other primers for that long!

It would be non-visible areas, basically some covering coats over filler before the final coat. They would only be shot in high humidity and then brought back into a shop with a dehumidifier that keeps things around 55%.

When it comes to something as important as primer, this is something that I would play it by the book and do what is recommended by the manufacturer. Shooting in high humidity can affect how the material leaves the gun and hits your panel, so it's not just about the humidity of the environment where it cures if you are moving the car around. I've had high humidity affect spray painting with cans before, so I don't see why priming with an HVLP gun would be any different in that regard.

As far as I know humidity just affects the level of gloss with the SPI epoxy.

Don

I’d be more worried about my air source humidity than the actual shop humidity where I’m using the epoxy primer. With high humidity air being drawn in by the compressor and the heat created by the compression process you’d need to have a good setup to trap the water and oil created.
Personally I have my compressor (automatic tank drain) in a separate building that is air conditioned (hate the noise of compressor in the shop) and run 1” pipe underground about 80’ where it enters shop area into a drop (to drain water) then a large Motorguard filter then 25’ of black pipe with drain drops for general air and finally a Devilbiss 3 stage desiccant filter for spraying, blast cabinet etc.
The long underground run of pipe is cool and gives the air a chance to condense any humidity drawn into compressor.
Of course you can wait until the humidity drops in the fall but you need epoxy and substrate to be at a minimum of 60 degrees.
I haven’t had any problems using clean dry air while painting in humidity of Long Island. My biggest problem is me sweating onto a panel lol.

If you call/txt Barry at SPI I believe he’ll just mention the longer induction time that I mentioned above. I think he’s posted that a time or two.

His premier definitely has impressive and “unique” qualities. I wouldn’t try spraying any other primer in less than ideal conditions.

My compressor is inside the dehumidified shop, not to mention having a super duper forced air after cooler and double separation before the tank, more separation and a MotorGuard filter after the tank. So supply air will definitely be dry. I'm a big fan of drying the air before it goes in the tank, the inlet to the tank is ambient temp even after 10 minutes of continuous running.

It's about 80 degrees and sunny out right now, humidity about 65% ... I should go out and shoot some today.


https://i.imgur.com/wtND8Bw.jpg

https://i.imgur.com/MQxpTot.jpg

Thanks for sharing your condenser setup I am doing something very similar. Can you tell me what you used to drop the voltage from 220 to 12 volts to run the fan. Thanks

Tim,
The fan is 120v, I split the 220v in the pressure switch and ran one leg of the 220v, and the neutral to the fan so when the compressor comes on the fan comes on at the same time. Fan has three speeds, I just leave it on high all the time.

In the second photo you can see the large gray 220v line going into the pressure switch, and a smaller black cable, the smaller black cable is the feed to the fan.

Really happy with the way this setup is working, seems to be much easier on the compressor, not sure why that would be, but it seems to be the case. It's quieter and seems under considerably less stress when pumping at high pressures (set point is 175 psi)

In this setup the additional fan not only cools the aftercooler it also blows additional air across the compressor heads.