Spraying lacquer

When spraying lacquer, is it recommended to maintain a wet edge - as one would do with paint - or is it OK to apply mist coats. Have applied two coats of lacquer and there appear to be a small number of anomalies in the surface. Wiped the surface thoroughly with mineral spirits before spraying - temp was approx. 75 F and the humidity was low, approx. 20%. Regards, Doug
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wrote:

A mist coat is a misnomer. It is still a full coat, simply thinner than others. If you don't believe it, mist some finish over your dried lacquer and take a look at the texture.

OK... white spots, dog hair, orange peel, dog tracks, the face of Charles Dickens?
Seriously, this is like saying, "I don't think my car is running right. Can you fix it?"

Was it water based lacquer?
Was it solvent based lacquer?
First problem, mineral spirits. Unless you allow it to dry completely (depends on conditions) you will get bad spots in your finish where it will separate. You should clean your surfaces with naptha or better yet, lacquer thinner. In any even, wait a half hour AFTER you are SURE it is dry to apply your finish. This is the time you mix your finish and set up your gun.
With no details, no one can help you. Did you spray from a rattle can? Did you use high pressure? HVLP? A CAS gun?
Have you sprayed lacquer before?
There are a lot of finishing guys around here, but no one can help you unless you take some time and properly and completely describe the problems, what kind of finish you are using and your equipment.
Robert
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Robert,
Thanks for your reply - should have known to provide more information in the original post.
As you previously suggested when I inquired about finish recommendations for red oak, used the shellac sanding sealer and rattle can semi-gloss solvent based lacquer, brand is Watco.
The surface anomalies appear to be very small circular areas - likely very small bubbles (?).
The surface is clean to the eye and touch before spraying and the work area, while not a clean room, is free of loose particulates.
If I use lacquer thinner to wipe the surface of a solvent based lacquer - will that tend to remove / soften the previous lacquer coat?
Have not previously sprayed lacquer wood finishes - although have done airbrush painting of models with enamel and lacquer and painted a full size motorcycle with catalyzed urethane.
From your comment regarding the use of mineral spirits, suspect there may have been slight residual mineral spirits that caused the indications.
Surface appeared dry - however did not wait a min. half hour before spraying - although at approx. 20% humidity the mineral spirits appeared to dry quickly.
Regards,
Doug
wrote:

A mist coat is a misnomer. It is still a full coat, simply thinner than others. If you don't believe it, mist some finish over your dried lacquer and take a look at the texture.

OK... white spots, dog hair, orange peel, dog tracks, the face of Charles Dickens?
Seriously, this is like saying, "I don't think my car is running right. Can you fix it?"

Was it water based lacquer?
Was it solvent based lacquer?
First problem, mineral spirits. Unless you allow it to dry completely (depends on conditions) you will get bad spots in your finish where it will separate. You should clean your surfaces with naptha or better yet, lacquer thinner. In any even, wait a half hour AFTER you are SURE it is dry to apply your finish. This is the time you mix your finish and set up your gun.
With no details, no one can help you. Did you spray from a rattle can? Did you use high pressure? HVLP? A CAS gun?
Have you sprayed lacquer before?
There are a lot of finishing guys around here, but no one can help you unless you take some time and properly and completely describe the problems, what kind of finish you are using and your equipment.
Robert
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Now you're going. Watco rattle can solvent is a good quality finish, and is now made by Rustoleum. I don't know of a Rustoleum product that isn't pretty good to excellent. Good choice.
> The surface anomalies appear to be very small circular areas - likely very

Since rattle can lacquers don't need to be shaken, we can rule out infusion of bubbles from the can.
Given the facts you described, I would GUESS, - key word there - that the bubbles were due to the mineral spirits continuing to "outgas' or dry under the lacquer. The lacquer has a much higher VOC content and will skin over rapidly.
Any remaining heavier oils (lower VOC) that is in the wood will continue to outgas, but at a slower rate. The gas is trapped under the drying skin, and then you have bubbles since the gas has no where to go but out. Leetle bitty ones.
But the gas has to go out, right? I won't stay trapped, that's for sure. And since mineral spirits are much lower VOCs than the one found in lacquer, you may have the culprit.

That would support my best guess above.

NO! You will have a mess you cannot fix unless you are ready to belt sand your project! This is what I would do (YMMV, right?):
1) sand the surfaces in question as smooth as possible
2) Brush the surfaces as clean as possible, then blow them off with your compressor and and nozzle.
3) Clean the surfaces with naptha. It isn't as hot as lacquer thinner, so if you are fast with just enough naptha to get your tack cloth damp, you can get your surface clean with no surface melting
4) Apply a coat of lacquer (not sanding sealer) and allow to dry 24 hours. Remember, you are repairing a damaged finish, not starting a new one. Be patient.
5) Sand this coat as smooth as possible. Still see the bubbles? Sand, clean, and repeat #4. Don't forget to wait the 24 hours. This allows the resins to harden enough to make your sanding cleaner with less tiny scratches, and help prevent "pilling"
6) When you are smooth, apply another coat or two to get the desired finish and call it a day

Same principles. You are probably just a little off track in your prep.

Me and mineral spirits have a frustrating, checkered past. In some cases, it can prevent good adhesion and even sabotage finishes that is is actually used to thin. I will use it as a thinner or a brush cleaner, but nothing else.
It is thin enough to get surprising penetration into wood, but it doesn't wick away and evaporate quickly leaving you to guess what you will have under your finish when using it as a cleaner.
And if you have uneven amounts on your cleaning rag (like a wet corner or side) you can even see your cleaning stroke marks when dying wood or with some clear finishes. This is particularly true when refinishing. Imagine my horror (nothing less...) when I saw this happen on an antique mahogany door I refinished.
I was so embarrassed I stripped it, dyed it, and refinished it again on my nickel.
Good luck, Doug. Let us know how you come out.
Robert
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Robert,
Thanks! for the excellent advice.
Appears the problem was self induced - really hate it when that happens.
However, now I know better and will no longer use mineral spirits as a wide down aid.
What is the preferred method for spraying lacquer from a rattle can?
I understand to not apply heavy coats - just not sure if maintaining a wet edge when spraying is considered a heavy application.
There are no doubt degrees of wet edge - and will have to learn the best application method in the school of hard knocks.
Thanks again for the benefit of your experiences.
Regards,
Doug

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Glad to be of some help, Doug.

Read on....

When you spray lacquer, you may need to spray more material than you think to get a professional grade finish. Most solvent lacquer recommended applications are in the 3 mil range wet, which will dry to +/- 1 mil dry. It is so accepted, it's almost universal. If you don't have a painter's mil gauge, try to spray the thickness of a dollar bill. It's about right.
If you are spraying less, especially consider the low humidity, you may starve the previous coats of the ability to resolvate (blend) into the the new coat, as well as negate to the new coat's ability to dissolve the fine lacquer dust overspray.

Like I said earlier, I am glad to be of help. I have had to learn a lot of this stuff the hard way, the expensive way, and the frustrating way.
Once you really get in the middle of it, you realize the complexity of it all and understand the finishing is a craft unto itself.
Anyway, good on 'ya for not giving up and getting back in there to fix your minor (remember... everything is relative!) mistake.
Check out this link for some good info. At the bottom third of the page is a good, illustrated description of how to spray.
Note the illustration of keeping your wrist perpendicular to the work. VERY important. No arcing, no other movement should be there; your arm should look like it is going back and forth on a rail when you spray.
It will also tell you to adjust the spray pressure. Obviously, you can't do that with a rattle can. The way you adjust pressure from a rattle can in regards to the disbursement of the material is to find how far from the target you hold the can. In this case, depending on the nozzle, it could be anywhere from 6" to 10", again, depending on the nozzle.
Practice your distance and pattern on a piece of finished cardboard. You know, the shiny stuff with the color pictures on it like appliance boxes. Don't bother practicing on a brown, cardboard box. It will absorb your solvents so fast you will never get an accurate read on your pattern.
Once again, good luck.
Hey... don't you owe us a picture from last time?
;^)
Robert
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wrote:

Jeez... I can't even keep my train of thought to the bathroom and back...
The link:
http://www.rentrain.com/content/1/56/280
Remember, the bottom third "for excellent results" sis what you are looking for on this page.
Robert
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Robert,
Again - this is invaluable advice and greatly appreciated.

When spraying the lacquer, I placed a bright light so I could clearly see the reflection off the wood's surface, and see whether the material was going on light or too heavy. Luckily got no runs - may have been too light on a pass or two.
Low humidity down here (Houston) is not the norm - although the past several weeks we have been getting regular cold fronts through that drop the humidity way down. 20% RH is really rare.

Need to get this finished - and done right, best I can - it is part of a present for my dad.

I did move the can parallel to the work piece surface, as I watched the wet edge progress - so remembered something from the past.
Results should be more rewarding next coat as mineral spirits will not be used for cleaning.

Can sure provide a picture - where should these be posted?
Any required limitations on file size?
Best Regards,
Doug
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wrote:

Great technique. This is called a "rake light", and for that purpose I have 4 sets of "two on a stand" adjustables on hand for use when I am painting or finishing. They are good even in the daytime.


Hey... you're over there with Swing and Leon. I am up the road in San Antonio, a scant 210 miles away. Similar weather here this week, and the Chamber of Commerce couldn't invent better weather. Clear sunny skies and 72 today. 70 tomorrow.

Anything else comes up, post away. I think you are over the hump, though.

I would say go with any of the free services. At the barbecue forum, they like Imageshack. At the knife forum, they like flikr and photobucket. All have free areas. There are lots of them available.
Your ISP may even have some space set aside for you. Just post the link here to the pics and we'll find them.
Robert
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doug wrote:

No, it won't "tend" to soften/remove the lacquer it WILL do so.
You didn't say what you were spraying. If it is small enough, try this to perhaps fix your problem...
1. spray a wet coat
2. put it in a closed box, small as possible
3. let it sit for an hour or two.
The new wet coat dissolves/blends with the previous messed up finish. The closed box slows drying time to enable the dissolving/blending. If it doesn't work, just sand the messed up surface smooth and spray again.
BTW, the closed box thing is also useful if you get blushing. "Blushing" is a whitish appearance on what you sprayed and is caused by trapped moisture. It occurs mostly during periods of high humidity and is caused because the can propellant (LPG) cools the lacquer when it (the propellant) goes from liquid to gas and that causes condensation.
--

dadiOH
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To get an idea of how lacquer reacts with mineral spirits try accidentally mixing the two. My experience is that lacquer thinner will thin oil base paints with usually no problems but mix mineral spirits with lacquer will cause it to curdle. So when finishing with lacquer, you really don't want any trace of mineral spirits to damage your finish.

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On Tue, 20 Jan 2009 00:27:44 -0600, "Douglas R. Hortvet, Jr."

I found that misting creates a bumpy surface. Lacquer dries very fast so there is little time for leveling. Best to spray onto a horizontally flat surface. Your humidity is somewhat low, temperature OK.
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Thank You for the reply.
20% humidity is rare in Houston - although the regular colds fronts making their way down here lately - much lower than normal humidity has been somewhat routine.
Using a can there is no way to adjust the material for temperature and humidity - per the instructions the temperature should be above 55 F - the high end is not a factor now.
Recalled from the instructions for paining models to first apply light mist coats, to facilitate adhesion. Once these are dry - go back and spray a full color coat.
Thanks again for your helpful comments.
Regards,
Doug

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I have found the two tricks to succesful lacquer are first proper thinning and conditioning, which is different for different days and different projects and second dual direction lay down (Just my made up name for the operation.)
Example of lay down on a table top. Spray with overlapping strokes from one end to the other making sure you get an entire wet surface. Immediately lay down another coat of overlappig strokes at 90 degrees to the first strokes. This is most important for non-flat surfaces where you have moldings or crevices to make sure things are covered from all angles but also very important for flats too to ensure total coverage and emough material for flow uot to flat.
Of course proper spray technique, keeping the gun perpendicular to the surface all through the stroke, not changing the angle at the ends as is the natural tendenancy. Also, spray lots of test on cardboard or something that really shows the pattern and loading and tweak the spray adjestment to get a nice smooth laydown. Keep in mind that you will lay down two coats so your output can be just about not enough after one coat.
On hot days use less thinner and maybe flash control additive. On cooler days thin more but don't spray when it is too cool and use a blush control additive to let the moisture get out before it is trapped under the filming surface.
The only time I use "misting" is if ZI have a problem with the laydown and then I just mist with pure thinner or 90% thinner to try and get blush out or flatten heat bubbles of wash off flash or overspray powedreing.
wrote:

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Thanks for the detailed comments!

Since I am using a rattle can - thinning and conditioning are not options - must make do with the material as is.

Would using this technique be a problem if the first passes were already mostly dry / tacky?
The work piece is flat and approx. 7" x 18" - rather small, and have been spraying along the long direction.

Will sure remember this - although would have to upgrade from using rattle cans!
Thanks again.
Regards,
Doug

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Douglas R. Hortvet, Jr. wrote:

With standard nitrocellulose lacquer, you can "flow coat" it with a highly thinned coat that will remelt the existing coating into a very smooth surface.
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Yup... that is the ONE thing that bugs me about WB lacquers. No melting. That, and not catching a buzz during the cleaning of the guns....*sworf*
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Robatoy wrote:

Me too...
There _is_ enough melting for rub-out, but far from enough for true flow coating.

That is such a *guy* smell. I love that smell! For hours and hours after the real solvent is gone. My wife freaks out about "that smell"...
Then again, I like the smell of burnt Avgas, burnt Racing gas at the track, and burnt JetA, while it makes the ol' lady sick!
WB just doesn't have the attraction...
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B A R R Y wrote:

All quite nice, I'm sure. What I like is the smell of boats... that "marina" smell. What is it that makes it so unique? Oil and gasoline mixed with fishy stink? I've never been able to figure it out.
--
See Nad. See Nad go. Go Nad!
To reply, eat the taco.
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