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Vinyl Image Cracking After Clear Coat

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SW101

New Member
Hey guys,

I have an MDO sign with a large printed image on it made of 3m vinyl that is laminated. I clear-coated the sign with automotive clear and now (2 years later) the printed image is starting to develop tiny cracks under the clear.

I know I recently read on one thread the best thing to do is to not clear, which is advice I may start using if there is no way to clear and make the sign last longer for the customer.

But my question is do you think this image is cracking because of the clear I used? Maybe I should have used Frog Juice or something similar instead of automotive clear? Or could it be more of an issue of not spraying the clear correctly?

The wood and the paint on the wood and my sealed edges are holding up beautifully but not so much the main vinyl image.

Obviously, I want to do better and make my printed images last as long as possible on my signs so what suggestions and advice do you all have? How long do you guys tell customers a sign with a printed image will hold up?

Any help is greatly appreciated. Thanks!
 
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SW101

New Member
Unclebun, never thought about this but that makes good sense.

Weyandsign the vinyl was IJ-35C and the laminate was Scotchcal 8518
 
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unclebun

Active Member
Although I have never clearcoated a sign that was installed outdoors, we have made digital prints on cast media, NOT laminated them, and they were used on vehicles and helmets that were then clearcoated. We have never had any problem with durability of those. Our go-to media for those is Avery 950 (a cut vinyl) or Avery MPI 1105.

I have never actually clearcoated a sign because dating back over 30 years ago when I started, the people who taught me to paint and letter signs said that clearcoats actually accelerate the aging and damage of paint and lettering.
 
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somcalmetim

New Member
Laminates and Vinyls have to be paired properly so they expand and contract at the same rate or you will run into de-lam problems.
Adding a painted clear coat on top of that only adds to a three layer sandwich you are trying to hold together with glue. If your clear coat doesn't expand/contract at exact same rate as your vinyl you will also run into problems.
If your print is cracking under the clear coat I would assume the vinyl shrinks in cold more that the clear coat.
 
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rcali

New Member
I agree with somcalmetim.

I am newly in the vinyl world but old in the paint and finishing world. From my painting knowledge and what I understand of substrates and materials, rates of expansion and contraction may be your issue.

Was the sign specked for automotive color and clear coat? I am not saying you did anything wrong, I am just curious because with a surface like mdo (mdf, wood, anything porous really) I was trained to try to use lacquer and not automotive paints. I do not know if it would have held up better over the vinyl but it would move better with the moisture and temperature fluctuations on the mdo than automotive paint does.
 
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citysignshop

New Member
Lots going on there....a photo would probably help us armchair trouble-shooters!
a couple of observations;
-auto clear has a LOT of solvent, assuming you sprayed it.
(Don't ask me why Frog Juice seems to be better, it's like frickin' magic or something. gotta be the good deadly isocyanates in there!)
-the solvent will soak into the laminate, and vinyl, and attack the adhesive, causing some issues.
- the lam and clearcoat are kind of duplicating the same function. If you use a higher grade laminate, like 1170c you avoid all the mess and cost of spraying some incompatible clearcoat, and it can be eligible for various MCS warranty by 3M.
- the decals you see clearcoated on helmets....usually the painter is a pro, and dusts on several dry coats, so most of the solvent flashes off in the air. the rough pebbly coats serve as a barrier to the topcoat, which is put on wet and results in the gloss desired.
- for the most durable outdoor sign, is all the prep and cost of MDO really the solution? Look at your finished cost, and compare to a properly supported sheet of aluminum or .....? Most wood signs I see are painstakingly sealed with many coats of paint and edge sealer, and are then destroyed by the chimp that drills a hole and installs with his 187V cordless HeWalt drill!
Moisture invades at fasteners ...unless properly sealed and given space to expand and contract.
Just sayin'. :)
 
Gino

Gino

Premium Subscriber
Most of the answers here are kinda spot on for various reasons. However, I believe the real question is your technique of applying the liquid clearcoat. When clearing over a motorcycle fender or police car door via spraying, ya generally do it in many many light coats and build up over a period of time. In fact the first two maybe three coats would be what we call dry coats..... barely a mist. After that, we would start to build it up. After doing van murals and sh!t for years, we could have 25 coats of clear on those things. You wouldn't need that many, but your first approach must be small until you have the vinyl sealed properly. If you do it in just 2 or 3 coats and close together time-wise, you're dead in the water.
 
Modern Ink Signs

Modern Ink Signs

Premium Subscriber
Never clear coat over vinyl. You are just asking for trouble a few years down the road.

Case in point - the problem you are having now.

Vinyl/Lam does shrink (yes even cast). Your clear coat is not. Thus the cracking. I believe manufacturers say not clear coat over their products. Not 100% sure as I have not looked at this in a very long time.
 
Christian @ 2CT Media

Christian @ 2CT Media

Active Member
Modern Ink Signs said:
Never clear coat over vinyl. You are just asking for trouble a few years down the road.

Case in point - the problem you are having now.

Vinyl/Lam does shrink (yes even cast). Your clear coat is not. Thus the cracking. I believe manufacturers say not clear coat over their products. Not 100% sure as I have not looked at this in a very long time.
Click to expand...
This is not true, entirely. While traditional paints and clears would have an issue, they make automotive paints and clears that can expand and contract for body panels like urethane and copolymers designed to flex instead of crack. You can clear coat over vinyl; you just have to use the right ones. A better option would be to find a flood liquid coater for your panels.
 
visual800

visual800

Active Member
you cannot us automotive clear over laminates on prints. I have done this before. When i clear over prints i scuff them very lightly and laydown a very fast thin coat of clear, let that cure and then flood it, I dont know what is it about learing over laminates but it does not work. In the past when i first did this the clearcoat would eat up the laminate but it will not not affect the print and will last a very long time.

automotive clearcoat is slightly felxible it has to be to adhere to urethance bumbers and other components
 
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