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Now that you mention it, I do see that reference to low temperature in the link - thanks to DuPont, btw. That's something I wouldn't have expected. Usually it's the higher temps and faster reducers that lead to orange peel. I have no experience painting below about 65 deg and I prefer to be up in the 70's, at least for topcoat. However, I think you should have been OK at 55-60. I just don't like to go that low as a precaution. The 70 deg indicated in the tech sheet is pretty much universally accepted as a standard reference temperature to predict paint dry times. Generally, cooler would take longer and hotter would be faster than noted. About three weeks ago, I applied some 170 to one of my AC-B fenders. We had three or four nice days that were well into the 60's, near 70. I was able to apply the 170 and 182 surfacer at that time. I wouldn't have attempted it at all below 65, but that's just me. I never got a chance to apply the topcoat. The weather turned cooler, down into the 40's and 50's during the day and has stayed below 60 since then. I am hoping to get the color on this week since the forecast is for temps up into the 70's by midweek. I guess you could say I really haven't experienced any temperature problems since I just don't paint below about 65 or above about 85. I paint outside so I have to work with the weather. I have no choice. The 170 I used hadn't been opened since last year. It took a lot of stirring to get everything uniform. Perhaps that could be some of your problem. Since you didn't have the problem with MTK, then the tip size and air pressure would not appear to be causes. You mentioned that it appeared a little thicker than you remembered from the last time. That could be due to the cooler temperature, but I don't know. I think that the painting surface, the paint itself and the ambient air should all be about the same temperature for the best result. I do have trouble with a cooler paint being the cause of orange peel. I would expect just the opposite. On the other hand, I understand there will not be a proper chemical reaction with the catalyst below 50 deg. I don't know if that would affect the flowout - possibly it could. However, you could make the same argument with the MTK (assuming it was also in the barn) and you didn't have a problem with that. Sorry to ramble here - just throwing out some thoughts. Did you say (or mean to say) you used a new batch of 175 catalyst for the mix? I know it's extremely poor to blame materials but it is possible, although unlikely, that you got some bad catalyst. If you have some of the old catalyst left from last time, you could try it out on some scrap just to eliminate the catalyst being the possible culprit.
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