Wrinkles in Lacquer

      Recoat window? Catalyzation? What could be causing this defect? December 9, 2004

Question
What would cause wrinkles in curing lacquer, besides oil and surface contamination? I was using my new precat nitro (with a booster catalyst) today and noticed that on a few of my back panels, I got some pretty wicked wrinkles. The lacquer went on smooth, then the wrinkles appeared when curing. I had just finished spraying an entire cab with no problems at all.

The only things I can think of that I did different on these pieces was shoot the lacquer pretty heavy, and I didn't lay down a misted tack coat first. Can this make that much of a difference?

Might this also have something to do with the fact that I'm using a boosted precat lacquer? The lacquer seems to dry really quickly, and I'm getting a lot of overspray. I'm using this lacquer unthinned, too. What should I do - thin the lacquer, or retard it? I'm not getting orange peel, and it seems to be going on just fine. I just don't want any more wrinkles.

Forum Responses
(Finishing Forum)
From contributor J:
I'm not familiar with this lacquer, but it sounds to me that you are dealing with a critical recoat time. That, or… If I remember correctly, didn't you add more catalyst to the second coat or were you just recatalyzing part of the batch from yesterday?

Rule #1 in finishing: Don't celebrate until the job is done and the check is in hand. (It's bad luck!) You've got a solvent reaction creating the wrinkling. Talk with your rep or a finisher familiar with this pre-cat, who will give you advice on what you should do.



From contributor D:
After you boost the pre-cat with more catalyst, what is your pot life? The longer a material is catalyzed and a reaction is taking place, you start losing chemical resistance properties. For example: You boosted the pre-cat on Wednesday and (assuming you are self-sealing) on Thursday, used this material to seal with. Now on Friday, even if you used a fresh batch over Thursday's sealer, you get wrinkling. I know it sounds complicated, but understand that this material will keep reacting in the pot even though it still sprays fine. It may turn out that you only sealed several pieces with the older material on Thursday and had to mix a new batch. In a normal precat lacquer, there is so little catalyst that the true reaction is coming from the air. I still think you can find a regular pre-cat to do your job under normal finishing conditions without having to "boost" it.


From contributor J:
To tell you the truth, I have never heard of pre-cat that had a booster additive. Isn't that why they call it pre-cat?


From Paul Snyder, forum technical advisor:
Wrinkles are caused when a cross-linking finish like catalyzed lacquer is partially dissolved by a solvent. Since the finish cross-links, the solvent can't dissolve it completely and only makes it swell up and wrinkle.

If you put down a heavier coat than usual and then sprayed the next coat before it had a chance to cure enough, that would cause the problem.

Get the technical data sheet for the lacquer you're using and find out the recommended wet mils per coat and re-coat time. If the temperature is lower than listed on the tech sheet, the humidity is higher, or you use retarder, allow more time between coats than the sheet recommends. Check how heavy you're spraying the finish with a wet mil gauge and stay under the limit.

Contributor J, the brand of pre-cat I use can be catalyzed the same way. That basically makes it a post-cat. It cures faster with the added catalyst.



From the original questioner:
I am using the product right after I catalyze. I do not hold any of the product over. It's basically: catalyze>shoot. From what I understand, this should be the best way to do it.

So if I did exceed the wet mils limit, this could have caused the wrinkles?

Do you think that product curing too fast could have anything to do with this problem? Fast cure is the goal, but I don't want to cause any more problems.

Like I said, other than this weird little problem, this stuff is perfect. I'm just trying to figure out what caused it so I don't have to go down that road again.



From contributor D:
Without knowing the formulation, it is difficult to predict if you applied too many mils. The problem I have is that pre-cats are generally a lacquer with a cross-linking resin added to give slightly better chemical resistance. They still have plasticizers in them that need time to dry. My point is that if you speed the reaction up too much, you are not getting a completely even cure. It will be spotty and certainly will open you up to spot wrinkling. If you want to turn a pre-cat into a post-catalyzed product, why not start with a properly formulated product? Add the catalyst when you're ready to shoot and move on!


From Paul Snyder, forum technical advisor:
Wet mil thickness is important for a couple reasons. If you get the total film too thick, it'll be subject to cracking. But for the wrinkling problem, laying down a thick coat, like you described, will slow the cure time. If the first coat isn't cured enough when you apply the second coat, the solvents in the second coat will partially dissolve the first coat and cause the wrinkling.

Keep the first coat within the manufacturer's limits and give it enough time to cure before you spray the second coat. For example, if the manufacturer says to apply a 4 mil coat and allow it to cure for 3 hours before recoating, but you sprayed a 6 mil coat, you'll need to wait longer than the 3 hours.

Contributor D brings up a good point that may be involved. Is there a waiting period before you can use the lacquer after catalyzing (induction period)? Did you measure the catalyst precisely? Stir it in very well?



From the original questioner:
I'm following what Trinity told me to the letter. The lacquer I'm using is LC-209, and I was told it has a lot of hard resin in it. I was told to add the catalyst, 4 oz. to the gallon. Instead of adding all of it at once and having it sit around, I am measuring out the appropriate amount and mixing in the cup just before shooting. I did not know that there could be a waiting time before shooting. I'm usually shooting within minutes. Should I wait longer, for the induction, as you say?

Like I said, the only things I can think of that I did different with the pieces that wrinkled were that I did not tack coat, and I basically just shot a heavy coat on the piece. With my other cabinet, it turned out fine. With that, I just kind of built up the layer slowly - misting on layers till I got the thickness I wanted.

I'm thinking that I should just build up the layers slowly from now on. I'm also considering retarding the mix just a wee bit to get a little better flow out and less overspray.



From Paul Snyder, forum technical advisor
I went to Trinity's web site and looked up the tech sheet for the LC-209. The tech sheet doesn't have much information.

Give Trinity tech support a call and find out if there's an induction time with the booster catalyst, if the LC-209 is self-sealing, what the max recommended wet mil thickness is per coat, and max number of coats (max dry film thickness).

The viscosity is pretty low, so it shouldn't need to be thinned depending on your spray equipment.

Tech support should be able to tell you how to avoid the wrinkling. Spraying a number of light coats instead of a couple wet coats isn't a route I'd want to take; too time consuming.



From the original questioner:
Paul, thanks for the info. I'm not experienced enough to make heads or tails of viscosity ratings - I did note the "no thinning usually required" statement on the LC-209 data sheet.

My paint supplier told me I wouldn't want to exceed 3 coats of this product, as the surface might be prone to crack otherwise (due to high solids). I'm using 2 coats of Trinity's vinyl sealer under this, and he took that into account.

For what it's worth, it was coat number two that did the wrinkling. The first coat had dried overnight.

I don't know… I'm still wondering if this lacquer's super high dry rate has something to do with it. That's why I was considering using a bit of retarder. It would help with the overspray, anyway.



From contributor D:
This is just my concern, but I think you may increase the wrinkle with the addition of retarder. The longer the topcoat stays wet, the more it will wrinkle.


From contributor R:
Sometimes two coats of vinyl can make a finish prone to wrinkle, since the vinyl is soft and catalyzed products tend to shrink aggressively. Something else to think about is sanding burn-throughs, especially with a thick coat. Once you cut through the top skin, the solvent in the next coat will get under it and cause a wrinkle, again compounded by the vinyl, which will remelt. As already stated, shoot a lighter coat and give it a little longer time to dry.


From Paul Snyder, forum technical advisor:
Just to add to the good points contributors D and R made, check with Trinity about using a catalyzed sealer under the lacquer. One coat of sealer is enough and a catalyzed sealer may be the answer to eliminating the wrinkling.

If you have to turn the air pressure up too much to atomize the finish, causing excessive overspray, then a little lacquer thinner will make it atomize at a lower pressure and reduce the overspray.



From contributor N:
The overnight dry is the key piece of information which you've supplied. You are certainly hitting a recoat window. Fifteen hours is just enough for the catalyst to begin to kick, but not enough time for the catalyst to completely cure the first coat. Shoot the second coat within two to six hours and this shouldn't happen. Trinity's Tech Support should have the final word, but this is my best guess based on other precats. Also self-seal. There's no need for vinyl sealer with this product. I had this exact situation with Sherwin-Williams Acrylic Conversion Coating. Overnight just didn't fit into the recoat window, which they of course claimed that the product didn't have.


From contributor I:
I would be more prone to suspect the sealer than the first coat not being cured well enough. It seems to me that if the first coat was still curing, we would be talking about solvent-pop, wouldn't we?


From the original questioner:
Okay, its starting to make sense now. Seems like I would have been okay if I had either waited longer to recoat, or shot a second coat a few hours after the first. It would also make sense that I saw the most wrinkles on the pieces that I shot the heaviest coats on. When I let these pieces dry overnight, I didn't even bake them in our hot room.

I'm going to try again tomorrow shooting lighter coats, and after letting the pieces sit in our hot room for a couple of days.



From contributor J:
I bet your head is going to explode with all this input on your new lacquer. Isn't finishing fun?!

Besides getting a little harder finish with the booster catalyst (this may be also the reason that it dries real fast, besides being formulated with acetone to reduce V.O.C. emissions), why do you feel the need to use this? After all, it is a pre-cat, correct? I'm thinking this booster catalyst is a little too hot and temperamental in its effect within this system. Just cut out this stuff and it saves you a little money. No worries about wrinkling and everything is back to normal with a pre-cat that dries quicker than your previous brand.



From contributor G:
My bet is that it is the sealer. If he's adding catalyst to his lacquer, shouldn't he be doing the same to his sealer? Precat or not.


From contributor J:
Yeppers, I always catalyze vinyl sealer under any catalyzed topcoat.


From the original questioner:
I understand what you are saying about the sealer. It makes sense, but the one reason I don't think it's the sealer is that the first coat didn't wrinkle. It was the second coat of the lacquer that did. That makes me think that it was some sort of recoat window thing.


From the original questioner:
I shot my lacquer today. No wrinkles. I used slightly less catalyst. I also kept the coats light, misting up the lacquer slowly. I'm not sure what the deal was, but it looks like as long as I keep the coats light, and give a good amount of dry time in our hot room in between, I should be okay.


From contributor D:
By keeping the coats light, you are in effect allowing less solvent to attack the previous coat.


From contributor G:
Might be over-catalyzing. Crinkle is also an adhesion problem. Surface tension of the top coat pulls tight as it cures. If not adhering to below, it will crinkle. If the window is wrong, the first coat lets go as the second coat flashes.

Keeping it wet too long on fresh coats at the narrow end of the window is also a problem. Retarder will increase the problem, as it lets the second coat have more time to react or soften the first coat.

If you didn't over-catalyze one coat and boost the other coat, they both have different windows and the hot acid in the catalyst just eats the uncured other coat, again allowing crinkle.

I've never added catalyst to a pre-cat. You can end up with it blossoming, much like a wrong mortar mix will effervesce through tiles forever. You have to just redo it or you might get by with a sand and recoat with a proper catalyzed mix.

If you have a 10-1 ratio, it's even more critical to be dead on with the mix, as opposed to a 1-1 ratio. Being off a little in 1 to 1 isn't much, but being off a little in a 10 to 1 ratio can be 20%!



The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor A:
Chances are you selected the wrong tip size and it became way too heavy causing it to curtain/wrinkle. My golden rules are: You can always put more on but you can't take too much off and always shoot a piece first and wait to see how it is going to react to the environmental aspects (humidity, temperature, etc) as lacquer can be deceiving from day to day depending on your environment.

Also, if you shoot a light tack coat and then come back to it a little later and spray a fill coat it always helps it hang on better. This helps especially if you are shooting clear high solids instead of high build lacquers. Another thought is maybe you used a lacquer sealer like a vinyl lacquer sealer that was not copolymerized with a small amount of amino resins. If you did this there is a chance that the acid catalyst attacked the non catalyzed vinyl sealer. There is so much to know from product to product and it is so easy for things to fail.



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