I work for a mobile auto paint company that has been using PPG for years but is switching over to Transtar and I'm the Guinea pig for trying out the system for this franchise. The bosses ordered all the paint system for me but I didn't get the reducer for transtar. I had to go paint a bumper for a dealership and after painting the bumper with clear the basecoat blushed horribly and I am sure I had waited long enough for the basecoat to flash. But without the transtar reducer I had to use PPG reducer. I didn't like this. I have never intermixed paint systems before and had no idea what could or would happen.

My question is can using a different reducer from a paint system cause basecoat blush? It wasn't that humid and the clear coat had the right activator for it. I tried twice to correct the problem but it happened again. I even waited longer the second time before spraying the clear coat. Please help! I have to go back and fix this bumper and don't want this issue to keep happening! Also the clear coat would get a ton of little bubbles or like pimples and looked bad even though it looked good at first. As it dried it got worse.

Blushing would be from humidity, too fast of an activator/reducer.
Sounds like there wasn't enough flash time for solvent to escape and it was trapped thus the little bubbles.

I was thinking that the first time I painted the bumper so I was told to cover the spots that blushed with basecoat again and wait longer. I waited about 20 minutes for the basecoat to flash the second time. I touched the surrounding masking paper and it was dry to the touch not tacky. I cleared the whole bumper again and the blushing happened a little again near the top of the bumper where it happened before and really bad on the left side of the bumper where I didn't reapply basecoat. When I cleared the second time the pimples showed up eventually. I do the painting outside in direct sunlight the company has an epa exception to do this and they've been doing it for like 20 years but I don't know why it wasn't flashed enough. Should I have waited even longer? It was like 85 degrees out and moderate humidity. The reducer didn't say anything about Temps and the activator was for the 80-90 degree range.

WKD_DRGN wrote:The reducer didn't say anything about Temps and the activator was for the 80-90 degree range.

Check the ppg product again. The reducer speed is indicated in the part number, last two digits. For example dt870 is a mid-temp (70 degree) reducer.

What exactly is the part number you were using? Also, blushing in the clear is usually an issue with the clear especially if the base was good and dry.

I would try and slow your reducer down or get the correct Transtar reducer the PPG should work but who knows. also when painting outside like you are I would get it out of the direct sun light. that bumper in the direct sun could be well over 100 deg. it will be interesting to see what you come up with as a cure. I've sprayed urethane clears of different brands for years in all conditions and never had this problem. I have seen some blushing with the base coat though, but very light.
Jay D.

WKD_DRGN wrote: I waited about 20 minutes for the basecoat to flash the second time. I touched the surrounding masking paper and it was dry to the touch not tacky. I cleared the whole bumper again and the blushing happened a little again near the top of the bumper where it happened before and really bad on the left side of the bumper where I didn't reapply basecoat. When I cleared the second time the pimples showed up eventually. I do the painting outside in direct sunlight the company has an epa exception to do this and they've been doing it for like 20 years but I don't know why it wasn't flashed enough. Should I have waited even longer? It was like 85 degrees out and moderate humidity. The reducer didn't say anything about Temps and the activator was for the 80-90 degree range.

You not only have blushing but solvent pop also. If the dew point and temps are high, the base and clear can blush when choosing incorrect products. You are popping because the clear is skinning very fast in the conditions you are shooting. It will not matter how long you let it flash; the clear is not drying as it should to allow all the solvents to escape. What Transtar clear are you using? They have many available.

The clear coat is euro spot & panel clear coat. I believe the reducer for the basecoat was 870. All of the painters paint outside for this company and pretty much in direct sunlight. No issues so far for them just me having issues but they are using full ppg systems. I also have a Turbine sprayer that has been rebuilt and it feels like the air pressure is extra low even for the system. I have brand new accuspray spray guns. So I spray two coats of clear coat every time maybe I am not giving that enough time to flash? I painted a mirror that day and everything went fine with that. Great even. I just don't know what I did wrong.

WKD_DRGN wrote:The clear coat is euro spot & panel clear coat.

What product number? What you provided is a spot and panel activator for two Motor City Euro clearcoats offered. Spot and panel is faster than the overall. You keep mentioning flash time but if the product is too fast for conditions you will have problems.
Slow it down with the right activator and try 5% reducer (for conditions) as recommended on the TDS. Thin wet coats. Reducer is optional and you will have to allow for that reducer to escape.
You must know what basecoat reducer you used. It was 870 or not. 870 is too fast for your heated conditions.

That's all the info I have right now cause I am not at work this weekend. So you are saying to use a different activator that is for the right temp AND pour reducer into the mix? Or also use a slower reducer for the basecoat? Sorry really confused. I have gone to school for this but have not been in the field as a painter for long at all. I used to work as a body man helper at a body shop so this is still fairly new to me.

And I only actually have the one activator and reducer I don't have a selection to choose from for different Temps which I informed them about.