Please let me blame my tape error…

G

GeoffW65

Promoted Users
Ok everybody. I’m on my first paint job.

I shot the jambs with base and clear over spi epoxy that was shot approximately 36 hours before. I have learned a lot since then, but hear me out:

- I then masked these areas to shoot primer on the exterior of the car and left the masking tape on for weeks and weeks because I had a lot of priming and sanding to do. I have learned a lot since (!)

- I then pulled the masking tape and had a few areas of the jambs pull the clear and base off with the tape.

It’s not the end of the world because I can still re shoot the jambs if needed. I took a much more conservative approach for the overall paint job and shot base over 2 hour spi epoxy with a bit of reducer in it.

I am chalking up my experience on the jambs to my idiocy of leaving masking tape on for a long long time (just didn’t know. Costly mistake). But my question is this: was 36 hours too long for the epoxy to cure before spraying the base? I know it was that long because I have pictures. Note that it was also in hot SC temps.

Thanks for any help or advice. I’m probably more apprehensive that the same thing is going to happen on the body panels…though the paint job came out looking pretty good for a first shot.
 
36 hours is fine.
The masking tape is best removed shortly after you are done painting. This will allow the "edge" to lay down and adhere better.
Getting the knack of pulling the tape takes a bit of practice. I find pulling at a slight angle towards the wet edge gives a cleaner pull.
 
dhutton01 said:
Never leave masking tape on fresh paint long term. Remove it asap.

Don
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This was worse. I masked over fresh paint in the jambs to start shooting primer, and left the tape in the jambs for weeks. Just a rookie mistake.

I'm glad the first two responses blame the tape. That's what I was hoping. Just painted the body this weekend and pulled all masking within hours.
 
GeoffW65 said:
But my question is this: was 36 hours too long for the epoxy to cure before spraying the base? I know it was that long because I have pictures.
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Too long, even worse used as a reduced epoxy sealer. IMO, after reduced epoxy getting it back on base after 2 hrs is enough. Don't wait spraying your jambs until all exterior primer is finished. The long term masking is a problem, but long term epoxy before base needs the chemical adhesion.
 
texasking said:
Too long, even worse used as a reduced epoxy sealer. IMO, after reduced epoxy getting it back on base after 2 hrs is enough. Don't wait spraying your jambs until all exterior primer is finished. The long term masking is a problem, but long term epoxy before base needs the chemical adhesion.
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The jambs were over regular unreduced epoxy but your point still stands.
 
IMO, base are the normal refinish products lower than chemical adhesion. Any base likes chemical and/or mechanical advantages. Sanding likes 400-600 mechanical under base. Mechanical any finer can cause adhesion problems. Chemical, if the epoxy starts to lose too much of the cure, the base will start to lose chemical advantage. Unreduced to reduced epoxy can change a lot. The sealer reduced 1:1:1 will need very little cure (as little as 30 minutes), 1:1:25% needs more time,(1+ hour) 1:1:10% more yet.(2+hours). Personally, I wouldn't wait reduced epoxy longer than 8 hours before base.
 
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I've been using SPI epoxy for a long time, but posts like this raise questions that I don't have answers to, party because I have never left tape on anything that long, and partly because I, like most of us, do not fully understand the physics of adhesion. There are other pieces missing, like true surface temps throughout the process, brand of base, speed of reducer, type of reducer, there are many places where this could have gone wrong. Of course, there are always places for our processes to go wrong. The trick is to stack the deck in our favor.

I have always been told that epoxy has a 7 day window, but as it turns out, it is sandable way before that, anywhere from 16 to 48 hours later depending on temps, and at my shop we have decided to always take advantage of that, to sand and add mechanical adhesion to whatever chemical adhesion exists. It's not cheap insurance, as it takes a lot time and grunt labor. But if you want to ensure an excellent result, it's worth it in my book. Sanding also reduces texture and offers an opportunity to fix imperfections.

As far as I am concerned, the 7 day window is just insurance for areas that can't easily be sanded. That doesn't necessarily go along with the science or with the Tech Manual, it's just my opinion.
 
I think what I'm learning from this is the following:

- Never, ever, leave masking tape on paint longer than is necessary...

- When spraying over epoxy, err on the side of "too early" vs. "too late" to ensure the preservation of chemical bonding.

- Reduced epoxy cures a lot faster than unreduced epoxy (knew this, but it's a lot faster than I realized).

- When in doubt, re-shoot a sealer coat before proceeding with base / clear.

Any more?
 
crashtech said:
I have always been told that epoxy has a 7 day window, but as it turns out, it is sandable way before that, anywhere from 16 to 48 hours later depending on temps, and at my shop we have decided to always take advantage of that, to sand and add mechanical adhesion to whatever chemical adhesion exists. It's not cheap insurance, as it takes a lot time and grunt labor. But if you want to ensure an excellent result, it's worth it in my book. Sanding also reduces texture and offers an opportunity to fix imperfections.

As far as I am concerned, the 7 day window is just insurance for areas that can't easily be sanded. That doesn't necessarily go along with the science or with the Tech Manual, it's just my opinion.
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I remember many years ago Barry said, the best adhesion is full strength epoxy sanded and top coated within the 7 day window.
Wouldn't matter so much if adding more epoxy, but it would before base coat.
 
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