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Old 10-21-2012, 10:18 PM
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humidity question

I recently flaked a roof with sg100 and before I added the clear a notice the center was getting a haze look. I felt it and I was able to feel moist. Now I live in so cal and we don't get a lot of humidity around here. So my question is at what level of humidity should I stay away from spraying. Now I sprayed around 5pm and the day was around 95 I really hot day.

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Old 10-21-2012, 10:39 PM
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Quote:
Originally Posted by angel85lx View Post
I recently flaked a roof with sg100 and before I added the clear a notice the center was getting a haze look. I felt it and I was able to feel moist. Now I live in so cal and we don't get a lot of humidity around here. So my question is at what level of humidity should I stay away from spraying. Now I sprayed around 5pm and the day was around 95 I really hot day.
95 is extremely hot to be painting. A couple of questions, what temperature of reducer where you using? Also your compressor, with high temps you will get condensation in your tank and your lines. Usually the humidity in the air just adds to the humidity generated when spraying. With the heat and if you where using the compressor it could be a combination. Do you have a drier on your compressor?
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Old 10-21-2012, 11:11 PM
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Originally Posted by 69 widetrack View Post
95 is extremely hot to be painting. A couple of questions, what temperature of reducer where you using? Also your compressor, with high temps you will get condensation in your tank and your lines. Usually the humidity in the air just adds to the humidity generated when spraying. With the heat and if you where using the compressor it could be a combination. Do you have a drier on your compressor?
95 was the high for that day when I started it was around 75 in the car port. I was using mid temp reducer. I have a water trap and a motor guard final filter. No drier.
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Old 10-21-2012, 11:12 PM
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Old 10-21-2012, 11:13 PM
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At that point I checked the temp on the roof and was 75
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Old 10-21-2012, 11:17 PM
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When you paint you almost need to be a weather forecaster and anticipate what changes you may have as the day wears on. If I was in Southern California I would slow my material down. With a medium reducer and the temperature getting warmer any moisture is going to show up. Did your compressor work hard before any painting?
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Old 10-21-2012, 11:21 PM
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Checking the temperature on the roof is fine but, it's the ambient air temperature and moisture content you have that makes a difference. The higher the temperature the more moisture it holds. Fore example, I live in Canada and we get a pile of snow every Winter. If our humidity content in Summer would be what it is in Winter, most of Canada would be a dessert. I hope this makes sense.
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Old 10-22-2012, 12:12 AM
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Originally Posted by 69 widetrack View Post
When you paint you almost need to be a weather forecaster and anticipate what changes you may have as the day wears on. If I was in Southern California I would slow my material down. With a medium reducer and the temperature getting warmer any moisture is going to show up. Did your compressor work hard before any painting?
It does since its only a 25 gallon 5hp
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Old 10-22-2012, 06:24 AM
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There's your problem...5 HP is usually fine, it's your reserve capacity that's killing you. Now I said 5 HP is USUALLY fine. In the compressor world many manufacturers lie and call their motors 5 HP when they truly should be rated at maybe 3 HP. The other thing you need to look at on a compressor is CFM out put. Paint guns use a lot of air and your compressor should put out at least as much or more CFM than the paint gun manufacturer recommends. 10 or 12 CFM isn't enough unless your using an air brush. 25 gallon reserve is excellent for filling a tire, not painting. When you paint you will drain that reserve tank very quickly and your compressor will run constantly...causing heat, causing moisture in your tank, causing moisture in your air lines and ultimately hazing off your paint work.

I just checked my portable compressor for my air brush and it's running 8.3 CFM and I can almost put that compressor in my pocket.

So in short...it appears to be a moisture problem. The moisture is coming from an undersized compressor, coupled with a warm ambient air temperature to really heat up the air your using causing condensation.

The fix, acquire a compressor that will more than handle the CFM requirements of the equipment (if you get a compressor that will handle more CFM and reserve capacity than you need it will last longer, reserve capacity should be minimum 50 - 60 gallon) your using and your problem will be solved.

I understand, simple, if only it didn't cost so much right.

Hope this helps
Ray
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Old 10-22-2012, 06:47 AM
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Another thing you should be concerned about in SoCal is the quick drop in temperature in the evening. It usually drops below the dew point at night, and with those high temps, the dew point will probably be higher also. So spraying outside in the evening is not a good idea.
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Old 10-22-2012, 06:59 AM
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Originally Posted by Chevymon View Post
Another thing you should be concerned about in SoCal is the quick drop in temperature in the evening. It usually drops below the dew point at night, and with those high temps, the dew point will probably be higher also. So spraying outside in the evening is not a good idea.
Absolutely correct, especially outside. When the air temperature dropped it condenses all the moisture held in the air from the earlier warm temperature. Think of it this way, an air conditioned car needs a condenser and an evaporator. Without these pieces when you turn on your AC you would get a cloud of fog inside your car. This is because you are quickly changing the temperature and releasing the moisture trapped in the warm air you're trying to cool.

Make sense?

Hope this all helps.

Best of luck
Ray
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Old 10-22-2012, 07:03 AM
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Quick note...on a hot and humid day my AC unit in my house can create a fog cloud so thick you'd think Charlie Sheen and Fidel Castro where having a cigar smoking contest in my living room.
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Old 10-22-2012, 09:11 AM
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Ok good info guys. I have a 60 gallon compressor but I have no 220 in my garage. Now it I had to paint small parts like I still have two what can I do prevent this. I have a few pieces left that need to be painted. The thing is I work 7 days a week and get off till 500 pm. Will days with less humidity or using a heat gun during coats help.
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Old 10-22-2012, 09:28 AM
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Quote:
Originally Posted by angel85lx View Post
Ok good info guys. I have a 60 gallon compressor but I have no 220 in my garage. Now it I had to paint small parts like I still have two what can I do prevent this. I have a few pieces left that need to be painted. The thing is I work 7 days a week and get off till 500 pm. Will days with less humidity or using a heat gun during coats help.
OK, I'm going to try and give you a cheaper fix for your problem. You still have to paint small pieces and you have a 60 gallon compressor but no 220 in your garage. Why not run a line from your 25 gallon compressor to the tank on your 60 gallon compressor. Let your little compressor fill up your 60 gallon tank. Now, I don't know what CFM your small compressor puts out so you may have to run it for a little while, shut it down, let it cool off and repeat until the 60 gallon compressor is full. Let your little guy cool off completely and start to paint. This should help with your mechanical moisture issues.

Days with less humidity will help and would be recommended...heat gun...NO...NO...NO. Your asking for more problems. It's way to easy to surface dry and not cure your paint with a heat gun. Body shops with an air make up unit don't bake their paint in-between coats, and neither should anybody else. If you do this you stand the chance of top drying your product and when you put more product over top the solvents will react with what you just painted and crack and blister and mess up what you just painted. Even after your last coat, leave the heat gun alone. You say you paint after 5 PM, well, paint your pieces, go to bed, let nature and the chemicals do their job and admire your painted parts in the morning.

Thanks
Ray
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Old 10-22-2012, 10:49 AM
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Good advice widetrack. I wired it for 110 but after it fills to a certain point the motor will come to a stop. As the motor is not getting enough amp to fill the tank. I was reading other threads and.some recommended using a hotter reducer.
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