graying after clear over black..

[upncoming]

ok i sprayed plack on a set of shock tower brackets and let them cure for 15 minutes then i hit them with clear and let them cure for another 20 minutes. when i pulled them out one of them had a thick gray tent in it but the other one is perfect. where did i go wrong? could it be in the clear? temps where 375 for both cures.

[bzer1]

There are several things that could have gone wrong.

1. Over cure on one piece(most likely)

2. Not enough powder(potentially)

3. Blooming on one piece(least likely)

If I were to hazard a guess I'd have to say that it's most likely over cure. You might have a hot spot in your oven or the clear might be curing too fast. I've had problems in the past with milky clear coats. It turned out that most clears are low cure formulas. You might want to lower your cure temp a bit and your dwell as well. you might also let your oven temp drop below your cure temp...say 100* and put your parts in at something like 225* and cure at 325*, the check them at about the 10 min mark. I currently have 10 lbs of clear that has a cure temp of 275* for 10 mins. It will have significant over cure problems if I try to cure at 300*.

[upncoming]

i will try the 275 for 10

Originally Posted by bzer1

There are several things that could have gone wrong.

1. Over cure on one piece(most likely)

2. Not enough powder(potentially)

3. Blooming on one piece(least likely)

If I were to hazard a guess I'd have to say that it's most likely over cure. You might have a hot spot in your oven or the clear might be curing too fast. I've had problems in the past with milky clear coats. It turned out that most clears are low cure formulas. You might want to lower your cure temp a bit and your dwell as well. you might also let your oven temp drop below your cure temp...say 100* and put your parts in at something like 225* and cure at 325*, the check them at about the 10 min mark. I currently have 10 lbs of clear that has a cure temp of 275* for 10 mins. It will have significant over cure problems if I try to cure at 300*.