Plexiglas painting anomaly

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Re: Plexiglas painting anomaly

Postby Ms Wolffie » Wed Sep 02, 2015 10:25 am

LittleGreyMan wrote:Sorry if my post sounds harsh, no offense intended. My English is not polished enough to smooth things.


BINGO, I suddenly realise why some people get offended by what I say or what I write.
I was not born to speak English either (Danish) and I know I will never lose my accent when I speak.
When writing, I may be grammatically correct but like you, not polished enough to smooth things. (Never heard it like that before)
I believe that with English as another language, we never learn to beat around the bush :P
We become a little bit too blunt.
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Re: Plexiglas painting anomaly

Postby scottp55 » Wed Sep 02, 2015 2:51 pm

Xxray,
Zero experience with your material or paint, so probably out of line, but:)
"Orange Peel" used to be the biggest source of "Factory Seconds" when doing canoes/kayaks/sailboats/etc. when doing gel coats in both epoxy and polyester. It always turned out to be pushing the curing time, surface contamination, or static on the molds in winter months.
Usually several wipes with denatured solved two of them.
sorry for butting in :)
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Re: Plexiglas painting anomaly

Postby Xxray » Wed Sep 02, 2015 5:45 pm

Thanks for the input everyone, have read all with interest. Don't mean to get sensitive about anything, with me it is often the case of not what was said, but how it was said. We are all adults here, I treat people accordingly and only expect the same in return. Anyways, it was not even you LGM that I was addressing.

This for me has been an ongoing problem for years, but as I said earlier, sometimes they have come out fine doing nothing, so was never really motivated to find a solution. My interest in doing these very recently started again as I see a market for these, and all of a sudden old problems were back at my feet so I look for a solution.

As stated, more testing is needed to find a repeatable solution. My 1st test was to simply clean the surface, and that one came out perfect, not a single wrinkle.
2nd one with the same cleaning turned out near perfect, but with just enough flaws to make it scrap ... Really, with these as with many other CNC projects intended for sale, no flaw is acceptable, especially one that is so visually obnoxious as wrinkling. Most other mediums can be worked on and "fixed" after a cut, usually by sanding. But with these you are locked, if it wrinkles there is nothing feasible that you can do to fix it, it is ruined.
So it was stated that perhaps I did not allow enough cure time - Maybe, maybe not. I think I will try a test on some semi scrap [these are various plexi pieces I have that still have the protective paper on them, but will likely never be used due to their size].
One I will paint without cleaning, one I will paint after cleaning. Will let cure 3 days then scratch a couple X's in them to simulate an etch, then coat with clear and see what happens. If the cure theory is correct then they both should be fine. If the contaminant theory is correct then the cleaned one should be fine, the uncleaned trashed.
Would also like to do the same test but with only a 2 hour cure - With the other test, that should expose if both cure & contamination are factors, will update when able. But as also stated, there could be other factors at play, atmospherics, temperature and humidity to name a few. I am hoping is it not that complex, and I will not have to build a regulated chamber to produce perfect results every time !
.

Thanks again for comments and suggestions, I hope reading this inspires others to experiment and make their own. When they come out right they are very elegant and unique.
Last edited by Xxray on Wed Sep 02, 2015 5:54 pm, edited 1 time in total.
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Re: Plexiglas painting anomaly

Postby LittleGreyMan » Wed Sep 02, 2015 5:54 pm

Xxray wrote:I hope reading this inspires others to experiment and make their own.


Absolutely. This one in the to-do-list, but unfortunately, it is already too long. Experimentation is a long process which has to take place between customer orders.

Thanks again for sharing your process.
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Re: Plexiglas painting anomaly

Postby Mobius » Wed Sep 02, 2015 6:00 pm

Good luck with the testing. I hope you will post your results so that others may possibly avoid the hassle.
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Re: Plexiglas painting anomaly

Postby Ms Wolffie » Thu Sep 03, 2015 8:27 am

Perhaps this is your answer
viewtopic.php?f=29&t=23145&sid=9702ed615375460c6ff9d459363280b0#p165509
Apparently you can get the same paint with different bases.
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Re: Plexiglas painting anomaly

Postby Xxray » Thu Sep 03, 2015 8:31 pm

Thanks for the link, I'll read through it.

I'm not convinced cure is the prime factor, or a factor at all. There have been alot of good theories here, but none to explain why this only happens with plexiglas and not other materials, using the same paint/cure times.
This one pictured below as an example I did the other day. You'd probably never guess what it is composed of. I took some .5 mdf as a core and glued a piece of chimney flashing [which is very thin aluminum] on it. I spray painted it black, 2 coats probably hour cure for each if that, then clear coated it. I then etched the design, scraped away areas are metallic, or actually metal.
Not a single crackle and, like plexiglas, aluminum is not porous ... So if it was purely a matter of curing time or pooling, to my mind anyhow, this would happen every time, all the time and not just with plexiglas.

I think it is a matter of residue left from the protective film having a reaction with the clear, I have partially proven this but more testing is necessary.
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Re: Plexiglas painting anomaly

Postby Ms Wolffie » Fri Sep 04, 2015 10:49 am

Here is one reason why paint crackles:
Avoid Spraying When It’s Too Cold - Colder temperatures and rapidly dropping temperatures can cause the paint to crackle as it’s drying. Crackled paint can also be a real pain to fix, so if possible. Try to warm up the space that you are working in and keep it at an even temperature as the paint is drying.
Another one is here:
Lacquer paints will melt the underlying paints and cause this issue,(It's Hot) switch to an Acrylic and i bet you will not have any problems

And then again, everybody seem to have a theory but no answer from the manufacturers :(
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Re: Plexiglas painting anomaly

Postby LittleGreyMan » Fri Sep 04, 2015 4:29 pm

Of course, there is no major difference between aluminum and plexiglas as both are metals, except plexiglas, which is a plastic material :mrgreen:

AFAIK, aluminum is much more porous than plexiglas. Not at our scale, but at molecular scale, which is important with painting.

I also think the risk of painting incompatibility is higher with plastics.

And once again, you can have electrostatic repulsion with plexiglas, it won't happen with aluminum. Did you paint immediately after removing the protective film? This operation can generate electrostatic charges.
If results were better after "cleaning" the plexiglas, maybe it's because this operation discharged the plexi, not because it was actually cleaner.

BTW, the chimney flashing trick is a nice one!
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Re: Plexiglas painting anomaly

Postby Xxray » Fri Sep 04, 2015 4:51 pm

"electrostatic repulsion" I think is possible, yes I do tend to peel em and paint em.
LGM, you might be a borderline genius !

Flashing is handy to have around, cuts well too with a sharp bit and slow speeds. Nice when you want something to look like metal without actually being all metal.
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Re: Plexiglas painting anomaly

Postby Ms Wolffie » Sat Sep 05, 2015 1:39 am

I love my multilayer material.
Sometimes aluminium on top, sometimes aluminium as a second layer.
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Re: Plexiglas painting anomaly

Postby Xxray » Wed Sep 09, 2015 1:37 am

Finally read the directions of the rattle can.

Says dry to the touch in 20 minutes, dry to handle in 2 hours, fully cured 24 hours.
It says to apply 2nd coat within an hour. So far so good, but then it says if clear coat is used, apply within 1 hour OR after 48.

I would never be able to apply within an hour. I have to let it dry longer than that to get a good clear etch, which itself takes almost an hour.
I have also never waited 48 hours, so I'm going to try that and I will post back with the results.
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Re: Plexiglas painting anomaly

Postby Ms Wolffie » Wed Sep 09, 2015 3:23 am

I tried to do exactly that and sure enough, after 1 hour and before 48 hours it crackled and got as wrinkled as a chicken's backside :D
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Re: Plexiglas painting anomaly

Postby Xxray » Wed Sep 09, 2015 3:34 am

I do epoxy floors on the side, and have for years. I have done floors from 20x20' garages to 100,000+ square ft factory floors and stadiums. I know there is a "window" for applying a second coat of epoxy, and if you go outside of that window bad things can happen. That usually manifests itself as "outgassing" with epoxy, and it will leave 100's or 1,000's of variously sized bubbles all over the floor. Only fix is to regrind the entire floor and recoat, quite an expensive and time consuming diversion.
Stands to reason the same concept would apply for other paints, hopefully this will solve my problem. I will no longer be able to make them at a moments notice, but I could always stockpile a few pre painted blanks to have on hand when needed.
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Re: Plexiglas painting anomaly

Postby Ms Wolffie » Wed Sep 09, 2015 8:25 am

Great way of looking at it :D
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