2 stage urethane flash times

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PostPosted: Sat Apr 25, 2015 1:16 am
Hey guys, I'm preparing for my second attempt at painting a car with urethane paint. I want to avoid the problems I had the first time.

The worst of which was drips forming. When I got to my final coat of clear, it felt like it was a fine line between forming a drip and not getting a good finish. I was thinking my flash times were to blame. The tech sheet on my paint tells me flash times, but doesn't tell me how long to wait before I clear.

Whats longest I should wait before I start to clear over the basecoat? Also, whats the longest I should wait between individual coats of the base and clear? I think the tech sheet said recoat in like 20 min or so, but I'm thinking that's not long enough.

Last time I painted, I think I did clear like 3 hours after the basecoat. If I were to wait longer, I may run into the issue of having to go into the next day before I clear. That could easily be 10-12+ hours past the basecoat, is that too long?



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PostPosted: Sat Apr 25, 2015 7:08 am
what was the temp in the garage, and what temp of reducer where you using ? there`s fast , med, and slow temp reducers

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PostPosted: Sat Apr 25, 2015 11:32 am
For base coat, depending on the temp, usually 10 min between coats. Also base coat has a 24 hour recoat window before having to scuff it again. Clear coats, a few factors play in this, temp in garage, speed of reducer, how fast your air flow is for ventilation, your spraying techniques. But the tech sheet will tell you 20 min @75 degrees with med reducer. Your air flow if there is too much can cause a "skinning" effect. The top will create a "skin" and under that will still be wet. Your spray techniques are a big factor, spraying too thick each coat, spraying too close, going back over a light dry spot, spray guns travel speed. Because your in a garage will be different anytime you paint. The best thing to do is to have msds sheets for all your products see what environments they work in best and make the best decisions based on your environments.

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PostPosted: Sat Apr 25, 2015 12:51 pm
I wait a half hour between coats but I am not in a production shop. I also let the base flash off over night.
in the immortal words of Frank Sinatra "That's Life"

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PostPosted: Sat Apr 25, 2015 1:59 pm
It would help if you told us what brand of products you are using.
Clears are different in solids content and solvent make up so a "one size fits all" spraying advice won't cut it.
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PostPosted: Sat Apr 25, 2015 7:46 pm
I'm using Starfire brand

So given that I have medium speed reducer, and the temp won't be super warm when i spray (maybe like mid 60s), i should be able to let the base flash over night without problems then?

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PostPosted: Sun Apr 26, 2015 7:34 am
Read and follow the tech sheets for the products you are using, if the info you need is not on the sheet you need to contact the paint company and get your answers. I like to paint and let the paint cure when temps are in the 70-80 degree range, if it's colder I use a space heater to be safe.

For clear and SS topcoats, I stick my finger on some masking near where I started, the paint should be sticky but not stringy, then I know it's safe to put on another coat. If it says 20 minutes, I might wait 30 to 40 to be on the safe side... haven't had any problems so far

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PostPosted: Sun Apr 26, 2015 8:24 am
Paint for Cars doesn't strike me as the best place to buy paint. If they have tech sheets I couldn't find them.
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