Anyone have any advice on spraying nit cel lacquer in conditions of high humidity (other than don’t do it). Are there any additives to minimize the finish fogging? More or less thinner? Buy a dehumidifier? I can’t wait around for a dry day, we don’t have them in NY anymore.
Advise apprieciated.
Replies
Hey RJ,
I'm in N.Y. and I've sprayed lacquer over the last 6 months without much problem. I prefer dry days and really try to spray on those days but when I can't wait I add retarder to the lacquer. Follow manufactures directions and adjust as you need, it works.
Regards,
SA
There are slow evaporating thinners, called retarders, that you can use to avoid blushing. Your lacquer supplier should have a recommended retarder and the recommended amount to use. Use the retarder in place of, or in combination with, your regular lacquer thinner.
Failing that, you can use methyl amyl ketone (MAK) as a retarder. Use MAK in place of 10% of the thinner you usually use.
The slower evaporating solvent will cause the lacquer to sag or run more than normal - spray your coats a little lighter. Wait longer to scuff/re-coat.
Paul
The slower evaporating solvent will cause the lacquer to sag or run more than normal - spray your coats a little lighter. Wait longer to scuff/re-coat.
Very true. To get around that particular problem, I like to substitute MEK or Acetone for lacquer thinner. The hot solvent flashes off quickly and helps very much to prevent sags and runs while the retarder (I like PM Acetate) keeps the surface of the lacquer "open" to let the moisture out so that it won't blush. A great side benefit of using this blend is that overspray and orange peel are greatly reduced. Not only by the retarder helping the overspray to flow out, but also by the MEK (my preference) biting in very quickly and thereby allowing the overspray particles a greater opportunity to flow into where they land. I use this blend year around, personally.
One very cool use for this solvent blend is for fixing runs or sags on dry lacquer. Sand out the run/sag without burning thru it. Finish up with a very fine grit like 400 or finer. Then lightly mist a few coats on the repair spot with the MEK/retarder mixture and it will literally disappear and be as if it had never been sanded on. This is very handy when having to respray to fix a run/sag would mean putting more film build than would be desired. Although I've never tried it... from what I've read about Shellac, I'd bet that something similiar (using alcohol instead of the MEK perhaps) would work the same. With nitro lacquer, the MEK redisolves the surface of the lacquer into a liquid very briefly and the retarder allows it to stay open long enough for the sanding scratches to melt into the surrounding lacquer.
This blend also works great for removing minor white water rings from lacquer finishes too. With higher gloss lacquers it is sometimes necessary to mix a small amount of lacquer in with the mixture. But, only a very trace amount... just enough so that you're applying an ever so thin finish layer.
Regards,
Kevin
"I like to substitute MEK or Acetone for lacquer thinner. The hot solvent flashes off quickly and helps very much to prevent sags and runs while the retarder (I like PM Acetate) keeps the surface of the lacquer "open" to let the moisture out so that it won't blush."
Kevin,
The reason a finish blushes is because the rapid evaporation of the solvent cools the surface to a temperature below the dew point of the ambient air and moisture condenses on and into the finish (while it travels from gun to surface). Acetone is one of the fastest evaporating solvents out there. Adding it make matters worse.
Try this...Soak a rag in a little acetone on a humid day, wave it around a little untill the smell is gone. It will be damp and cold. That's from the moisture in the air condensing.
FWI to all, Try PPG DTL105 for thinning in high absolute humidity situations. If that doesn't work, wait for a better day.
Jon
Edited 6/25/2003 6:22:16 PM ET by WorkshopJon
Edited 6/25/2003 6:24:10 PM ET by WorkshopJon
What I obviously didn't say very clearly was that I don't omit the retarder when I use MEK and/or Acetone. The retarder keeps the surface open and negates the blushing problems entirely in my experience. I've never had any blushing when using this blend, and I've been using it off and on for the last decade+.
If I were using straight MEK or Acetone, sans anything else, you'd be absolutely spot on about the problems that would incur.
Sorry for the confusion.
Regards,
Kevin
Kevin - I'm with you that PM acetate is a good choice for a retarder and misting a coat of retarder on a lacquer surface will release blush or surface water rings, but I wouldn't recommend loading the lacquer with hot solvents (without the supplier or manufacturer's okay).
Lacquer thinner contains a blend of solvents, often formulated for the specific brand of lacquer. Adding a small amount of retarder (MAK, PM acetate) is generally accepted practice, though using the manufacturer's retarder is the best solution. Adding acetone or MEK can cause problems with the film forming process of the lacquer. The lacquer may seem fine, but can fail a lot sooner than it should have.
As a precaution, I'd talk to my supplier and probably post a question on the WoodWeb forum as well as the Wood Finishing Supplies forum before I added any MEk or acetone to my lacquer.
Paul
Edited 6/25/2003 6:52:01 PM ET by Paul S
I've been using this blend for many years and have had no problems. Good quality lacquer thinner usually containes MEK anyway. And I should have stated that I personally use MEK rather than Acetone. A friend of mine prefer Acetone... but uses it exactly the same way with PM Acetate.
I should point out that I don't "load up" the lacquer with any solvents. The max I've ever used was about a 20% reduction and that was when I was younger. Now days I prefer to reduce a total of aprox. 10%, of which MEK constitutes about 80% and PM Acetate the remaining 20%.
I actually first leaned this trick when I got a job painting high-end interior shutters at a relatively high production facility. Ditto for the repair trick that I mentioned. Anyway, this solvent blend with nitro lacquer has literally many thousands of hours of production application history just at this one production shop. These guys are charging the big bucks and selling to very high end customers. To date I've never heard of any failures of any kind associated with the shutters they sell. They've since switched to a water-based finish. But, even there they had problems with the manufactorer's suggested method for using it because the quality just wasn't good enough. So, they threw out the manufactorer's guidelines and reinvented their own system. To date they are still in business and still servicing the high-end shutter market nationwide.
If it makes anyone feel better about it... I've discussed my use of this blend with the local Sherwin Williams lab guys and they didn't express any major concern with it except to quibble about my ratio of retarder to MEK.. The guy who had this particular job (I'm writing this from my work computer) before I did used to work in the local S/W lab and I've inherited tons of formulas for making nitro lacquers (mostly pigmented colors) that he generated over the years. Every one of them includes a dose of MEK before any lacquer thinner is ever introduced.
Regards,
Kevin
Edited 6/26/2003 12:45:40 AM ET by Kevin
Edited 6/26/2003 12:50:58 AM ET by Kevin
Kevin,
To quote you from this and another thread,
"I like to substitute MEK or Acetone for lacquer thinner."
Then you say,
"I've got another book at work that also mentions Acetone's misibility with water in the context of expressing caution about using a lot of Acetone in nitro lacquers because it's misibility with water can lead to blushing problems."
So which side of the fence are you on? I'm just havin' some fun here, but...
Jon
I'd also mentioned in another thread that I prefer MEK to Acetone. I included Acetone largely because I have used it before, but mostly because one of my mentors loved using it and we got in several heated arguments over whether MEK or Acetone were better suited to the purpose for which we were using them. He favored Acetone and I favored MEK. If you look at a listing of properties of the various members of the Ketone family, you'll see that Acetone and MEK are easily the two that are most similiar to each other. So, it's quite natural and appropriate to discuss the two together IMO.
Anyway, the caution with Acetone and blushing is one of how much Acetone one can safely use and under what conditions. Just because Acetone is more prone to blushing problems doesn't mean that it can't be used without incurring blushing problems. It's an issue of proportions and conditions more than anything. I included it because it can be safely used in conjunction with a retarder. I've done so. But... MEK works much better in my experience.
Regards,
Kevin
RJ,
One thing I forgot to ask, Is your compressed air dry. If you are simply hooking a flexible (rubber) hose up directly to the compressor, no change in solvents is likely to help.
The air that comes out of my lines is very dry (100' plus run of gavanized pipe sloped and take offs done properly) Last night I sprayed a coffee table with lacquer during a t-storm. 98% humidity and 65 degree dew point. No blushing.
Jon
Just to give an update of sorts... I was searching thru Mohawk's website for an MSDS on a particular lacquer and on a whim decided to open up the MSDS for their No Blush lacquer additive. http://www.mohawk-finishing.com/mhk_cds/product_msds/M716-240.pdf
It contains both PM Acetate (they call it Methoxypropanol Acetate - same thing) and Acetone.
:-)
Regards,
Kevin
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