A query- I've not used polycarbonate before, but have a 6 ft square lightbox to reface.
The old 1/4" perspex faces were continually broken by vandals, so I suggested using 1/4" lexan or makrolon instead, for impact resistance.
It's all opal stuff- with green lettering. I want to spray it, (in mid green) instead of using translucent vinyl.
Possibly dumb question, but I'd like some opinions, please...
What's best- would krylon suffice? Automotive lacquer touchup cans? Enamel?
Any cautions & workarounds I need to be aware of?
(edited to add it won't be back-sprayed, it'll be done on the outside face.)
TIA!
[ May 13, 2010, 06:06 PM: Message edited by: Ian Stewart-Koster ]
Posted by Bill Davidson (Member # 531) on :
Well, it should be back sprayed. But, I had done vinyl front and back combinations. Remember, painting translucent is like painting candy apple top coats. This is why the back painting technique is a first up and down stoke, top to bottom across the panel, then a back and forth stroke across the whole length of the panel. Always wiping with a damp shammy between coats. Spray in a darkened room, with a light source Behind the panel to See the weight of the coat being sprayed. Plus if you can SEE the color being sprayed, it is TOO heavy a coat. Color is built up gradually. Then spray white over all to diffuse the light. HOWEVER, if the color is not Dense enough, reds will turn pink. Good luck! Bill
Posted by Mark Matyjakowski (Member # 294) on :
does it have to be a certain green that there are no vinyl colors close?
seems like less work to me to cut vinyl than to cut mask to/and paint ... unless set up to do it right (any of the paints you mentioned will either have to be fully opaqued or will look spotty)
Posted by Bobbie Rochow (Member # 3341) on :
Ian, I worked in sign shop about 20 years ago, spraying the lit sign faces. I remember mixing the paint SUPER thin, & it was a special kind of paint that was translucent, to let the light come through.
Bill is right, it was sprayed from behind, with a light source behind the panel so you could see how your coats were on the panel. We used a liquid mask I think called Gripflex, pink bubble gum smelling stuff. You had to use a respirator to spray it, & when it dried, we layed the pattern behind it & cut it with an exacto.
It would be so much easier to use translucent vinyl. Krylon would dry opaque, & no light would shine through it.
Posted by Ray Rheaume (Member # 3794) on :
If you can get the right color, translucent vinyls is a pantload easier.
Spraying's a bear on lighted signs. Too much and it becomes opaque. If the spray's not even, it'll look blotchy when lit. Krylon Fusion will stick, but it's too opaque. Candies adds a lot of cost and you need a clear adhesion promoter like X-I-M or PPG One Choice...more cost. Throw in the masking materials, clean up of the spraying equipment...I think you can see where this is going, Stewie.
Most jobs can be done in vinyl or paint, but truth be told, illuminated signs got more cost effective and far less labor intensive when translucent hit the market.
Now if we could just insure that it didn't get into the hands of those who think everything looks good in Brush Script.... Rapid
Posted by Ian Stewart-Koster (Member # 3500) on :
Thanks for the comments-I wasn't planning on using any masking materials- just cutting through the coversheet, peeling off what's to be removed, and spraying, using the remaining protective liner as the mask.
It'll be opal material, so I can't backspray it- the other undamaged side of the sign was done the same way: vinyl-over-opal-background.
Most of the time the lights are off- they only turn them on at night- it's a motel- so opacity isn't too much of an issue- if the writing looks a bit dark at night, the background will be white, so it'll still be legible.
Two rows of text are wider than I can do in our plotter- that's why I shied away from trans.vinyl
As it's 6 ft square, I can put the piece down on the bed & plot the design in the cover material on the cnc router, or even project & hand cut it in not too much time. That's why I was thinking of paint, rather than vinyl.
(edited to add I've done perspex back-lit signs years ago, hand-cut, and sprayed with lacquers. I just wasn't sure about the polycarbonate & any difference in material treatment. I'm told it gets 'tortured' by lacquer thinners...!)
[ May 14, 2010, 12:07 AM: Message edited by: Ian Stewart-Koster ]
Posted by Bill Davidson (Member # 531) on :
Yes, it does get Tortured by lacquer thinners. It tends to Melt the layers off, as poly is just layers of Saran wrap and this is why it will not break. It's like metal folded many times for Japanese swords or knives. Spraylat and Gripflex are two brands for back painting. You can use Gripmask for any paint the uses thinners as it is water soluble. Just wet it when everything is dry and it will peel of quite easily. If you do want to front paint. I would paint black opaque first, then the color over the top so you don't get a motteled globbey light thru the color. cheers, bill
Posted by Dale Feicke (Member # 767) on :
I'm with Bill on this one, Ian. If you have to paint it on the outside, I'd use a black coat first, so the light won't come thru the lettering. No splotching that way.
I personally would tend to stay away from aerosols. They just normally don't hold up well, long-term....especially out in the sun and weather. I'd be more tempted to cut the liner, like you said, and roll the paint on.
Do a test on a corner though. I did some aluminum sheets a couple of weeks ago, that must have been from two different batches. A couple of sheets had a blue cover sheet, a couple had green....for whatever reason. When we rolled the paint on (industrial enamel), the green cover sheets lifted around the edges of the letters, the blue didn't. Go figure.
Posted by Brad Ferguson (Member # 33) on :
Ian,
I bet that Krylon would work just fine. Its adhesive is very aggressive and should bond. Since color is not an issue, spray black first to opaque it, like Bill said.
Am I correct that Opal is a color of Perspex? It is a white?
..........
Regarding lacquer thinner and polycarbonate: not even all the GripFlex thinners are recommended. Some are too hot. I think the one we usually use for back-spraying polycarbonate is T2003.
.........
We recently had to duplicate a logo on a back-lit Lexan face. The logo color was a gradient, blending from ivory to fire red. The 8'x8' faces wouldn't fit in the booth, so the decision was made to spray the GripFlex color onto clear vinyl, then plotter-cut the logo and install it second surface to the clear plastic. The vinyl sheets (4'x10') were full of static, especially after I DA-sanded them with 400 paper. But after stapling the sheets to a wooden frame and thouroughly washing them with water followed by a quick lacquer thinner wipe, I removed most of the static with an alcohol/water mix and a chamois. I then wetted the entire back side of the vinyl, the liner side, with water in a plastic dish soap bottle just before painting the vinyl side with GripFlex. This totally removed any static left from handling. The vinyl sprayed beautifully and the gradient turned out very smooth. I then back-sprayed the entire sheet with GripFlex white, though I may not have needed to, since the entire back sides of the faces were eventually covered with translucent vinyl.
I regularly wet the back of plastic when I back-spray, a trick I learned from Paul Berkshire of Peoria in my early days. This goes a long way to remove the splotchiness that is often caused by static in the plastic. It can be disconcerting, though, when a drop of water decides to run down the back side as your spraying. It looks exactly like a drip running down the FRONT side and it makes your heart stop for just a second.
Caution: Be careful that you staple the vinyl to the frame with the correct side exposed, else you will be spraying the liner. I will not admit that I did this in case my boss is reading.
Brad in Kansas City
Posted by Ian Stewart-Koster (Member # 3500) on :
Hi Brad, nice helpful little tale!
Thanks, yes, opal is the colour- it's a semi-opaque & semi-translucent white, as opposed to a dense white.
I think I've been convinced to use translucent vinyl- it's a colour like Kelly green.
Any opinion on wet or dry application? Normally we do everything dry.
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