Winter/summer season adjustement

serjik911

Promoted Users
Hello everyone!
For last two months my main clear was spi production. On first 5 gallons of it I did small adjustements, while spraying, found the best one for me, and the last 10 gallons of it I sprayed almost the same adjustment. So, I got pretty used to it, always had it the way I wanted and no runs, no dry spots. Today, however, something changed.
Today, I got 2 cars, 2 Dodge caravans, both front ends, both same color - pbu, dark blue. The first thing I noticed- got too much overspray from sealer. Second - base dried a bit too quickly. But didn't give it too much attention. And then clear. It sprayed way different than it was yesterday and and any day for last couple months. The drops were too big, and I had to readjust the gun. After finishing the second coat, I found one light run. And again, for the last 2 months I didn't have any of them! So I was mad at myself that probably I did a mistake somewhere and slowed down for a second. But next car, I'm doing same stuff and getting a run again! So now I pretty sure it's not just me, but something is changing. I have always same clear-production, same hardener, I have always same temperature- 65 while spraying . The only thing that really changed outside- we getting warm temperatures and snow starts melting. The humidity goes up and even at my home yesterday I turned out humidifier.
So my question is- does humidity affects the way how you spray? And if it does, what adjustments should I do?
Thanks
 

serjik911

Promoted Users
so googling and searching didnt give me a lot of info, but devilbiss has interesting small graph on their website. based by it, humidity does affect the spraying. wonder if i can adjust it by adding a bit more reducer. gonna try 1.2 tomorrow
 

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texasking

Promoted Users
Humidity will make it dry faster. Warmer temps will make it dry faster, but also reduce the viscosity. Adding reducer would be going the wrong direction. If you're getting runs, try bumping up the pressure at the gun 2-5psi.
 

serjik911

Promoted Users
Humidity will make it dry faster. Warmer temps will make it dry faster but also reduce the viscosity. Adding reducer would be going the wrong direction. If you're getting runs, try bumping up the pressure at the gun 2-5psi.
bumping pressure up but its already dries too fast?
 

serjik911

Promoted Users
26 psi for tekna te20, fluid and fan all out. On second coat tried to close fluid a bit and didn't give me much better result
 

texasking

Promoted Users
Did the material just come off a truck? If the clear or hardener was cold, it could cause the problems you were having. It takes a long time for the material inside the can to reach room temperature.
 

serjik911

Promoted Users
Did the material just come off a truck? If the clear or hardener was cold, it could cause the problems you were having. It takes a long time for the material inside the can to reach room temperature.
No it wasn't. It's was sitting for last 2 months same as a other 17 gallons I bought of spi production clear.
The only thing is different is humidity in the air
 

jlcustomz

evil painter
Temperature of product itself put into gun could be different now. Viscosity may have been thicker before & now is closer to more normal average.
Less fluid into gun or smaller tip gun is first thought there, however other changes may need to be made now , such as slower hardener or adding a little retarder to what you have now to slow it down. Always good to have retarder on hand.
Everything needs to play together & temp & humidity changes will trip you up in many various ways. You may have been compensating before for colder fluid temps. Fluid temps are as important as air temps & should occasionally be checked with infared gun also.
EDIT

Just as an example with unrelated commercial water acrylic paint I spray at work around this time of year , in early morning I may thin twice as much with alcohol to both thin & dry faster, then by later morning the same mixture dries in gun tip & need to go back to usual average water & product to slow drying.
 
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AAE

Learner
You're in Minnesota? Can't be that much of a temp/humidity change yet. The product isn't the issue. Go back through your set up steps. Maybe the tip or air cap has some dried product choking it. Maybe, the gauge got bumped and changed pressure. Maybe, I don't have a clue.
 

jcclark

Oldtimer
If you want to slow it down but not reduce the viscosity because of runs,
replace a little of the reducer with retarder.
You can actually use less total reducer/retarder mix (upping the viscosity) and
still get it to slow way down and increase flow a lot without the runs.
 
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