So let’s say I have extra slow activator and I’m spraying universal on an 80 degree day. I really wouldn’t need the retarder? But if it was 85 or above like you mentioned retarder would help?
Or if I only had slow or normal activator on a hot day that really calls for a slower activator I could add some retarder to the mix to slow down the flash ? Enabling me to keep it wet long enough to not be spraying into a dry edge or dry spray settling on my clear before I can finish?
Main use is for hot weather. Secondary use is for getting the clear to flow more. Flow coating, is one example but something I wouldn't recomend someone try unless they have a lot of experience spraying. 80 degree day no real need especially if you are using slow or very slow activator. I would never use anything but slow or very slow at 80 degrees or over irregardless if I used some retarder with it. The fast activator shouldn't be used above 75 and even then only with small jobs. Motorcycle tank, fender, etc.
The retarder shouldn't be used as a substitute for the correct activator for the temperature you are spraying in.
Summary: Universal Activators and Retarder
Fast activator= Sub 75 degrees single or two panels maximum 65 or so (coldest I will shoot clear at) it would work well for multi panels. Personally I will not shoot an overall with fast even at 65-70 degrees. I would go with slow instead. (I would not use retarder with fast activator.)
Slow activator 75-85 degrees multi panels, can be used for overall especially if closer to 75 than 85. Retarder can be added in smaller amounts to help with open and flash times and to allow for the clear to flow as intended or slightly more.
Very Slow 80-95+ degrees and higher, Lower temps will flow more (be careful) above 85 should be considered mandatory if doing an overall. Retarder can be added in larger amounts to help with open and flash times and allow for the clear to flow as intended.
Retarder is not intended to be a substitute for the proper activator for the temperature you are spraying at. If you try that you are own your own so to speak. Might be ok or it might not work very well.
That's about all I can tell you about retarder.