learning to spray lacquer

[Dan of SC]

I,m working on the third guitar that I've sprayed Behlen stringed instrument lacquer on. First I sand the wood down to 220 grit. I start with 2 coats clear or amber shellac, wait a day, sand with 220. Clean with a tack cloth, spray with unthinned lacquer to start. I try to put on an even coat, moving the gun just fast enough to not have a run. I wait 45 minutes, spray again and continue until I have 5 coats. I wait a day, sand with 220, spray another 5 coats. I keep going in this manner until I've applied most of a quart. then the last 3 coats or so I thin a little more and more until the last coat is about 1 part lacquer to 3-4 parts thinner. Let dry for 2-3 weeks. I have to start with dry 220 paper and sand a good bit to get all the orange peel off before I can start with the wet paper up to 2000, then buff. The finish looks OK but according to what I've read, I shouldn't have so much orange peel. It probably takes most of an hour with dry 220 to take off all the orange peel. Is this normal? If not, what am I doing wrong? Any help would be greatly appreciated. Danny Gray

[charles Tauber]

Everyone has his or her preferred sequence.

I didn't see anything in your finishing sequence about filling the pores of open-pored woods. Usually, that is done fairly early-on in the spray sequence. If one wants a high-gloss finish, the open pores must be filled either by packing them with a filler material or by filling them with finish, then levelled. Finishers often use a filler, rather than finish, because it saves time and money.

I also didn't see anything in your finishing sequence about levelling the finish, but for the orange peel. A method that I learned from a well-known luthier is to sand the finish about half-way or so through the sequence with very coarse sand paper (120 or so) to completely level the finish - most of the finish build is removed in the process, but not to the point of sanding through the finish. After levelling, a few final coats are applied, obtaining a relatively thin finish. Final sanding is then just to remove any texture from the spray gun. Your spraying sequence suggests a very thick finish.

If I recall correctly, you previously said you were using a compressor with a conversion gun with about 45 psi at the gun. I haven't used a conversion gun and can't tell you much about them - I've used traditional guns (45-60 psi @ 6.5 CFM) and HVLP gun/turbine. (True HVLP guns use about 5 psi, though I do know that conversion guns use a higher pressure.)

You may get better off-the-gun texture with the right combination of the following:

-the right viscosity of finish
-the right distance from nozzle to surface
-the right needle/orifice diameter
-the right spraying pressure
-the right "wetness" per coat of finish
-the right spray air temperature and humidity
-the right mix of air and finish at the nozzle

Finishing is a pain and often involves a lot of trial and error to get the variables just right. You may be able to consult the manufacturer of the gun (and the manufacturer of the finish (Behlen)) for suggestions for best setting for those variables for the particular type of material you are spraying (e.g. nitrocellulose lacquer).

[LouieAtienza]

It would take a lot of.shellac to pore fill an instrument. I'd use some kind of filller or epoxy. Alo, you can use 220 after your build coats but I would sand to at least 800 before spraying your final coats. If the lacquer doesn't flow out enough on the suface you can use a little retarder or xylene, but it will dry a little slower. I would wait at least a week or more before leveling the final coats.

Also, I start with 1000 to level off. A sanding block is a must. Auto body supply houses have one that's foam on one side and rubber on the other. Add a couple drops of dishwashing soap in your water. You have to use a squeegee or soft towel to check your progress at an oblique angle to see any imperfections. If you start with too heavy a grit you will never get rid if the scratches. 800 is the lowest I would go for spot touch up. If you can't get it perfectly flat with 1000 then you might want to reconsider your prep schedule. Once you get it perfect with 1000 you do the same with 1500 then 2000 if you want. Always use firm but pliable sanding blocks, never just use yiur fingers. It also helps to buy a couple extra blocks and cut them for the hard to reach spots.

I also use an HVLP conversion gun. You have to play with the air/finish mix a bit to get a good pattern. But if you you still get excessive orange peel, then

a. Your finish is the wrong viscosity. Your gun might have came with a viscosity tester, basically a cup with a tiny hole that you time.how fast it empties. I do it by feel with lacquer.
b. Your finish is drying too fast. Use retarder or.xylene to slow.it a little. Make sure you get a wet coat, but...
c. Do not make the coat too thick. If you do you should wait longer before the next coat. And if the orange peel is bad, use 400 to knock the high spots down before continuing.
d. Don't ever use cheap lacquer thinner. It has too much crap in it that will screw you up (like water.) Get a high grade thinner from Sherwin Williams. There is a reason it costs three times as much, it even smells different.
e. Back to retarder, a lot of what yiu have to do depends on the prevailing weather. Unless you have a climate control spraybooth. Usually the retarder helps solve the problem.

For the above reasons I moved away from lacquer and use a two part urethane finish from the automotive industry. They make different hardeners based on weather conditions (faster or slower, usuall slower hardener for hotter days.) One I am done with prepping the wood which I sand to 600, I spray one coat. I wet sand after 24 hours, starting with 1000 working to 1500. I then wipe down completely with naptha, then let it sit and dry, then wipe down with a.dry rag. I spray one nice coat, then a flash coat after 10 minutes. I start with 1500 firstm and if there are trouble spots I use 1000 minimum and work up to 1500. I then use 3M Trizact pads in 3000 and 5000, keeping my sanding unidirectional and akways with a block, even the sides and neck. After 5000 i go straight to Perfect-It glaze compound if I want a 'mirror' shine, but I find I love the look of the 5000 grit finish, like a hand rubbed lacquer look...

[jakeiboy1950]

Louie go into a good auto body refinishing shop and watch them go through the refinishing sequence on their jobs they achieve top class finishes with a minimum of fuss useing the correct process for every stage always working towards the next stage which will be finer smoother than the one before the end result will stand the test of time in a very harsh environment but all done in the most cost effective manner possible I only ever used 220 at the filler stage then moved quickly on to far finer grades, orange peel = paint to thick =wrong viscosity = use a viscosity cup and the seconds hand on your watch and read the manufacturers information sheet

[B. Howard]

Proper gun set up and spray technique will go a long way toward getting better flow out. For small objects like guitars I set my gun to give a 4" pattern with the aircap 4"-6" from the surface. Using the right size tip and needle for the material is very important, 1.2-1.4mm for most clearcoats gives good atomization. When spraying its important to keep the gun a constant 4-6" from the surface with the aircap square and parallel to the surface being sprayed. Even speed of the spray pass and proper pattern overlap also make big differences in surface texture of the coating.

Another thing is getting the right amount of wet film down in each coat. If the coat is too light it will flash before it flows and leave a lot of texture. Too heavy and sags, runs and solvent pops can get to be problems. I aim for a wet film of 4-5 mils for each coat. Having a mil gauge to measure this is helpful to get you dialed in on how fast to make the pass to get the desired coating weight.

Your last coat or flow coat is too heavy on thinner. Reduction past 20% is just not necessary and downright environmentally irresponsible. All that extra thinner goes into the air! And this is actually causing problems, as with lacquers every coat that goes on re-wets all the other material already on the surface, with that much thinner everything gets real soft and much of your intercoat sanding could be time wasted. A small amount of Acetone, say 5-10% will actually drop the surface tension much more than a standard reducer and yield better flow on that last coat.

This is only the tip of the finishing iceberg.....it is a whole other discipline requiring a new set of skills and tools.

[LouieAtienza]

Originally Posted by jakeiboy1950

Louie go into a good auto body refinishing shop and watch them go through the refinishing sequence on their jobs they achieve top class finishes with a minimum of fuss useing the correct process for every stage always working towards the next stage which will be finer smoother than the one before the end result will stand the test of time in a very harsh environment but all done in the most cost effective manner possible I only ever used 220 at the filler stage then moved quickly on to far finer grades, orange peel = paint to thick =wrong viscosity = use a viscosity cup and the seconds hand on your watch and read the manufacturers information sheet

What about my particular schedule is not expedient, cost effective, or least fussy? I have two coats basically and a completely finished guitar in 48 hours! An auto body shop is not as concerned with orange peel, in fact they need to.blend with the existing factory finish which can have some. There is also a movement in some shops away from coarser compounds.

I can afford to be a little.more particular because I am finishing a guitar, not an automobile. Also I attach my necks to.my guitars beforehand, which requires some care in sanding. Een then I don't spend more than 10 minutes with any grit sandpaper, if you keep the sandpaper wet and clean it cuts fast. I even considered a powered wet sander but it is really not necessary for.me.right now.

I already brought up use of a viscosity cup, so I don't understand the repeat. My post described some of the issues one faces with lacquer and how to deal with it.

[Howard Klepper]

Louie, I think he got your name confused with the OP.

[LouieAtienza]

Originally Posted by Howard Klepper

Louie, I think he got your name confused with the OP.

Aye, that's a possibility I didn't think of, trying to respond from a "dumb" phone....

I have to say good riddance to nitro lacquer. Now, what to do with about 3-1/2 gallons of it?! I bought a pint of Acme Finish1 and two small containers of hardeners, one fast set (lower temps) and one slow set (higher temps). I sprayed one acoustic (neck already attached) and a few electric bodies, and used not even a third a can of the finish. Very durable, yet just enough flex to move with the wood. The first few strokes with sandpaper is almost like the sandpaper is sliding over the surface, it's that hard. And that's after 24 hours. I even wet sanded and polished one body after three hours, though it is not recommended.

According to the salesman at Sherwin Williams, a properly applied clearcoat should be about 3-3.5mils thickness. Don't have a tester for measuring this however, but my initial impressions is that I do get a very deep gloss over a color basecoat or wood, without the wood looking like it's slathered in thick plastic. And as I love the look of nitro lacquer and shellac, I really have a hard time playing a guitar I feel I need to wear a cummerbund or put a chamois over my lap for fear of scratching the finish.

[B. Howard]

Originally Posted by LouieAtienza

According to the salesman at Sherwin Williams, a properly applied clearcoat should be about 3-3.5mils thickness. Don't have a tester for measuring this however,

You need a wet mil gauge. You use it to determine how thick you are spraying your wet film and then by using the solids content by % you can extrapolate the dry film thickness. One this to watch with modern poly coatings including 2 part urethane is there is a maximum mil barrier, usually about 5 mils total system. Don't exceed it or you risk serious film failure.

[KingCavalier]

Okay, I'm ready to try my first Lacquer job. I must admit, I'm pretty nervous. I bought a QualSpray 125 WB gun from Homestead. It has the 1.0, 1.2 and 1.5 setups. Also, I have Cardinal Lacquer and vinyl sealer. The OP says he sprays 5 coats per session and does so until most of the quart is used. He's concerned with he amount or Orange peel he gets. I didn't know any Orange peel was okay. Sounds like I just learned something very important.

My plan was to sand to 180, pore fill with Z-Poxy, shoot 2 coats of vinyl sealer and then only 3 coats of Lacquer per session. Sand level between sessions with 220 or maybe 320. I wasn't going to thin my last 2 coats, should I? Also, I wasn't going to spray more then 8 or 9 coats of Lacquer total

Any help is greatly appreciated

[LouieAtienza]

Originally Posted by KingCavalier

Okay, I'm ready to try my first Lacquer job. I must admit, I'm pretty nervous. I bought a QualSpray 125 WB gun from Homestead. It has the 1.0, 1.2 and 1.5 setups. Also, I have Cardinal Lacquer and vinyl sealer. The OP says he sprays 5 coats per session and does so until most of the quart is used. He's concerned with he amount or Orange peel he gets. I didn't know any Orange peel was okay. Sounds like I just learned something very important.

My plan was to sand to 180, pore fill with Z-Poxy, shoot 2 coats of vinyl sealer and then only 3 coats of Lacquer per session. Sand level between sessions with 220 or maybe 320. I wasn't going to thin my last 2 coats, should I? Also, I wasn't going to spray more then 8 or 9 coats of Lacquer total

Any help is greatly appreciated

I personally sand to at least 320 and preferably 400-600 on the wood, and no coarser than 600 between coats. You'll see those sand lines thriugh the next coats.

A far as thinning it deoends on the brand. Some are spray ready some not. In my experience, the indutrial stuff always requires some thinning and what you thin with depends on the situation. If yiu spray regular lacquer with no thinner you can end up.with a case hardened finish where it is softer underneath the.surface, because the surface will dry first and the chemicals won't out gas fast enough. Some lacquers are spray ready, thiugh yiu should obtain a data sheet to be sure. Your gun should have a viscosity tester as well, otherwise yiu will spit finish out.

Likewise I would not go more than 3 coats per session for the above out gassing reasons. Lacquer is a very thin finish and the key to to get the wood prep perfect to avoid rough sanding your build coats. Also always use sanding pads, never just use fingers only. Even on tight spots, cut small blocks to use. Use a couple drops.of.dishwashing liquid in yiur water when wet sanding. Wipe dry, then wipe down with degreaser (naptha), let air dry, then wipe, beteen sessions, because finger oils can cause problems.

[GolfSteve]

Originally Posted by Dan of SC

I start with 2 coats clear or amber shellac, wait a day, sand with 220.

One I start finishing I rarely use sandpaper less than 400 grit unless I really screw up. Sometimes 320 grit if I get bad orange peel. 220 works fine - BUT - it is so aggressive that you risk sanding through the finish, especially near the edges, unless you are really careful.

Originally Posted by Dan of SC

spray with unthinned lacquer to start

You need to match the viscosity to your gun settings so that you avoid orange peel. I usually thin lacquer about 10-20%. Viscosity cups are available at paint stores and your gun manufacturer can recommend a nozzle/pressure combination for that viscosity.

Originally Posted by Dan of SC

moving the gun just fast enough to not have a run. I wait 45 minutes, spray again and continue until I have 5 coats.

You don't want to put on too thick a coat - thinner coats are better. The problem here is that you need to give the coat enough time to off-gas before applying the next coat. 5 thick coats applied in rapid succession might be trouble. I spray a "wet coat"...just enough finish to get a wet surface that will flow out, but not "enough to not have a run". I wait about an hour before the next coat (the room is quite warm), and I usually only apply 3-5 coats a day before letting the job sit overnight.

Originally Posted by Dan of SC

I keep going in this manner until I've applied most of a quart.

Your target should be to have applied sufficient film thickness that you can level sand and polish and at the end of the process have sufficient finish left on the guitar.

Originally Posted by Dan of SC

the last coat is about 1 part lacquer to 3-4 parts thinner

That's pretty thin. Shouldn't hurt anything, but why do it? You have to level sand and polish after the final coats anyway. You should be able to get a very good level finish without excessive thinning. Also---a coat that thin is just asking for a run to happen on the critical last coats :-(

Originally Posted by Dan of SC

It probably takes most of an hour with dry 220 to take off all the orange peel. Is this normal? If not, what am I doing wrong? Any help would be greatly appreciated. Danny Gray

Once the initial levelling is done, then sanding goes quickly. The first time I sand (after the first 5 or so coats) takes a while - probably an hour - but after that the intermediate and final levellings probably only 30 minutes with 400 grit paper. Sometimes I use 600 grit for levelling. I always use a sanding block and am very careful near the edges where there is a tendency to sand through the finish. You can probably tell that I have sanded through the finish in the past. For a guitar that isn't too bad a disaster, but on furniture projects where I use stains and dyes more often, a sand-through is a disaster.

Spraying is an art and takes a lot of practice...I don't do that much spraying so I have to relearn my mistakes on every job.

[Jim.S]

As you can tell Danny there is a few ways to spray lacquer. I use pre-catalysed lacquer (nitro with added flexibility).

After surface prep, pore filling which I only go to a 240 grit I shoot 5 coats at 15min intervals thinned around 50/50 or 60/40 (sometimes I use a retarder depending on humidity). I let that gas off for 2 to 4 weeks then level with 400 grit wet. Then another 5 coats at 15 min intervals and gas off again for 2 to 4 weeks. Then I go over it with 800 wet up to 1200 or there abouts depending on what I have around. Buff with one of those 75mm foam pads with a polish on a small pistol air buffer. That's the short of it for a gloss lacquer, if you want the long version Allen on the ANZLF is a pro spray painter and has posted a good tute HERE

Jim

[gpj1136]

I thin just enough to flow evenly 4" to 6" from the surface depends on temp and humidity.
I spray no more than three coats 45 minutes to an hour between coats on the first day and very lightly sand with 400.
three coats second day 600. Three coats third day than let cure for a few weeks than micro mesh. If I'm not real careful I'll sand through with the micro mesh and need more coats.
Seems like it cures faster over the long run with less coats per day.
I am still a beginner but this seems to work well with only a light orange peel that polishes out easily.
I did notice a difference with quality lacquer thinner also. I used some cheap stuff and had some blush even when humidity was low. Switched to a higher quality and it flowed better with no more blush on the same day.

[Dan of SC]

[QUOTE=

Your last coat or flow coat is too heavy on thinner. Reduction past 20% is just not necessary and downright environmentally irresponsible. All that extra thinner goes into the air! And this is actually causing problems, as with lacquers every coat that goes on re-wets all the other material already on the surface, with that much thinner everything gets real soft and much of your intercoat sanding could be time wasted. A small amount of Acetone, say 5-10% will actually drop the surface tension much more than a standard reducer and yield better flow on that last coat.

[/QUOTE]

Brian, I got this final, super thin coat from a book sold by StewMac called "Guitar Finishing Step By Step" written by Dan Erlewine and Don MacRostie. I'm sure these guys know their stuff, but frankly I didn't learn much from this book. It's not for beginners, much of it was downright confusing. Thanks for your and other guys input. Danny Gray