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First post. This forum has been invaluable as I've taken up the sport and I thank you all. Recently retired (early) and just finishing...and finishing...my 6th. Reasonable success with French polish, varnish, EM6000 and, now, lamp-cured polyester. Hoping to pick "best one" for thin/tough/beautiful before further climbing the learning curve(s). With the poly, have had at least my share of dust craters, sand-throughs, repel spots, cure failures and witness lines. Started brushing - am pretty decent with a brush - but resorted to shooting outside a couple of weeks ago to try to overcome fatal dust craters. Have had a couple of near-perfect shoots to buoy my spirits but dust and flies convince me to build that booth I've planned for some time. Have read a lot - especially here - that has helped me to lay it out but some important questions remain and include...

Size of output fan(s)...and perhaps input fan
Will uncured poly foul a direct drive motor
Is positive pressure "better" than negative and what about a hybrid - using smaller/cheaper fans front and back
If I have fans at both ends, do I add the cfm to estimate the effective flow through the booth
What dust particles really matter (how big/small) and, with that in mind, best bet for inlet filter material/thickness/porosity
How much filter area front and back

My primary objectives are preserving health and improving quality and I absolutely will not shoot anything requiring "explosion proof" equipment. Not here, at least.

My shop is in a large finished basement that is above grade on one side. Central NH where is warm/humid now but mainly cold/dry. "Finish Room" is 10 by 15 room off the "Machine Room," with a door that will be weather-sealed. The exterior long side of the FR has a typical 12" by 30" basement window in the center of the wall about 6' off the floor through which I hope to exhaust. The opposite long wall shared with MR has a 4' door cutout in the center (and opposite the window) that I plan to board up to include a filter bank to inlet air from the machine room...and the rest of the shop that is heated by baseboard - about 1600' in all. The ceiling is 9.5' off the deck so I plan to build a platform between the inlet and output, effectively raising the booth floor 30" so that I will be shooting directly toward the window with the air inlet over my shoulder. So, the booth will be an open-ended affair about 5' wide, 7' tall and 8-9' deep. The output filter area could be 5' wide by 4' high...or less. This size in a commercial rig would probably have a 2000-2500 cfm motor. The input filter area might be the same, larger or smaller. To minimize dust, I'm thinking that more cfm on inlet and less on the outlet will pressurize the FM so that I won't contaminate it much when I go through the door, presuming I remember to turn on the inlet fan first. Or all that inlet fan business may be a waste of time. Dunno.

Okay, if you haven't nodded off yet, can you offer answers to my questions or, if you think I'm on the wrong track, suggest how I can most easily meet the objectives - health and quality - in the proposed space? I'm particularly concerned about the poly which, if uncured, might continue to be a hazard. Clearly, I can cure with the lamp anything that doesn't get through the outlet filters.

Now aren't you glad that I've confined my earlier forum participation to look, don't touch? :>)

Jeb

Hi Jeb and welcome to the forum.

Sorry I can't answer your questions about setting up a room for spraying, instead, I have a couple of questions for you. What kind (brand) of polyester are you spraying? I am intrigued by your "near perfect" shots as I have not yet found an advantage to spraying with the stuff from cureuv.com. Although I am told it can be done, I haven't found a way (including by spraying) of applying it thick enough to level out but thin enough not to run. So I've been brushing it on one surface at at time. This works, but I don't think it's the optimal approach. Ideally (and I've been told this also can be done) one should be able to go right from spraying to buffing. That would be nirvana.

Thanks,
Pat

_________________
There are three kinds of people:

Those that make things happen,
those that watch things happen,
and those that wondered what happened.

Jeb,

Explosion prof fans are still a smart move. If I had a place for building a booth, I would get the explosion proof fan as a must, regardless of the medium being sprayed. I recently saw a great booth that was part of an enclosed room (very clean) with an air filter in it, an explosion proof fan pushing air out of the building, and an entire wall built with HEPA filter material. Even the door was a big filter. The filters weren't thick, just good enough to keep everything on the other side. There were no air handling vents or ductwork on the inside of the booth area, only in the remainder of that room, so they kept all contaminants from getting in as much as possible. Of course the caveat is to not have the fan running when the door is open, or all that is a moot point.

_________________
"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."

My simple solution to the $700 explosion proof fan issue was to create a positive pressure rather than negative. I push air into the booth rather than suck it out.
The toughest part is sealing the room up tight enough so that fumes don't escape into my main shop, but other than that it works like a charm.

Good Luck.

Dave

Using the Greenlight Coatings stuff that came with the CureUV guitar package, Pat. I had similar experience to what you and David reported with brushing. Nibs and dust craters. With those attempts and the first few shoots, I think I cured too quickly in order to head off some of the dust issues so the finish hadn't flowed out as well as it will if you leave it for 10-15 minutes. I would level what looks like subtle orange peal but that mottled pattern seems to telegraph right through the whole coat so I'd get sand throughs before I had eliminated the defects. Tried buffing out without sanding out all of that mottled stuff and it just gets uglier.

Kept at it tho. I'm using P400 Fre-cut followed by green ScotchBrite and tacking off with a commercial tack rag. (Seemed much of my dust problem was caused by particles on the surface before I applied the finish.) Then shooting (outside) immediately with the guitar sitting flat. When I saw no dust craters after I put the gun down, I rushed the guitar into what will be my finish room and left it for 15 minutes and came back to find that nothing had disturbed the finish. Cured it and was able to start rubbing out with 1200 - CAMI, not P. Then 2000, then Buflex. Nice. This coat was heavy enough that it would have sagged a bit on a vertical surface. As it was, it tended to hill a bit at the rim, though I read that you can head that off by shooting the rim lightly before laying down rest of the coat.

I got a good coat on the sides before the one good experience with the back, mainly because the vertical surface didn't pick up any dust. With the guitar laying flat, I shoot the rim quickly and then the sides with overlapping horizontal strokes. Then shoot the top and take the guitar in to level. Cure the top only so I can bring it back out and lay it down on the cured side and shoot a bit more on the sides and then the back. Back inside to level, then cure the back and sides. The finish on the sides pools a bit at the bindings which is fine if it doesn't sag. I'm using Homestead's small gravity gun with a 1.2 mm needle at 29 PSI; three quick coats in a box pattern.

My present theory is that, by roughing, carefully tacking and immediately shooting in a clean booth, one can get a coat that's good enough to buff out without going through. Holding the guitar in one hand and shooting the whole thing may help to get enough finish all over, then keep it moving to preent sags. I'm not confident that a coat thin enough not to sag is thick enough to rub out, however, unless you get it just right. I've been hoping that you'd try the SimTech and report that it hangs better. If I understand the literature, it has more solvent in it so it will flash off enabling one to shoot another coat or two before curing which would solve the build issue. I'd try the Solarez if I lived down near Woody. Was 50 degrees here Monday night so any outdoor shooting will be restricted to deer pretty soon.

So, onward with the booth where I'll tackle this again, allowing for the possibility that catalyzed poly may be more expedient. Any thoughts will be very welcome, Pat. Good luck!

Jeb

Probably good advice, Don. As I mentioned, there's 4' by 7' doorway in the back wall - in addition to the side door - that could house 28 sq feet of filter. Think that's enough? Overkill?

Yes, the positive pressure notion is intriguing. I only have two doors to worry about - the one for continued use will be weather-sealed and the other will be the air inlet. All the walls and ceiling are painted sheet rock. Floor has carpet now but will be painted concrete. Any advice about how big the inlet filter panel needs to be, what sort of filters, etc? How should I house the motor so that it utilizes the whole filter panel and doesn't try to push 2000 cfm through a twelve inch section? Thanks, Dave!

Jeb

Thanks for the info Jeb. I'm currently in the process of re-finishing a guitar, changing over from a French polished finish which has worn, to the cureuv stuff. As I said, I've been brushing one surface at a time. I have found that the little bits of contamination sand out faster than the areas of not being level, such as the hills that you mention around the edges. I have also found that because the finish is so hard, it takes a lot of buffing to get it to a high gloss.

In an earlier post, I had mentioned the idea of using a BBQ rotisserie to rotate the guitar while the finish is leveling. I did rig that up and try it for the sides where vericle surfaces are unavoidable. It seemed to help, but not as much as I would have hoped. I still had some runs/sags that needed to be sanded out.

The folks that claim complete sucess and who apparently worked with cureuv to develop the product are at Third World Guitars near Miami, Florida. The main contact there is a fellow named Omar Jana. He says that they spray the whole guitar in three thin coats with about 5 minutes between coats. After the last coat they let it sit for about 20 minutes before curing with the light (they have one of the cureuv curing booths). He also says that they don't have any problems with runs or nibs. Omar is great to talk to on the phone, but not so great at answering email questions. They may do a video of how they do their finishing which would be nice. If I lived closer to Florida, I'd ask to go see their operation. I think he'd be OK with that as he seems to want to endorse the cureuv product. Perhaps I'll have to take a vacation this winter...

Despite the challenges, I am still mostly positive about this finish because of its durability. I can actually finish a guitar and then do final assembly without any wait time and without inadvertently marking it somewhere with a fingernail. The sanding out and buffing is more work than I had expected. I did try going from cure to buffing on a test board and it worked better than expected. I was able to buff out small bits of contamination and the finish looked great. Of course one of the absolute truths about finishing is that it's far easier to do a test board than it is to do a guitar and I don't know a way of getting the finish on the guitar as level and clean as I can on a small test board.

I am also interested in trying other uv cured finishes since I have this light. The one that I am most interested in trying are those from Admiralty Coatings as they, like the stuff from cureuv, have zero VOCs. They have three different coatings that have different properties with respect to how thick they can be applied and hardness. It would take some experimentation to find the best combination for finishing a guitar. The problem is they only sell by the gallon and at $200. per gallon, that's getting into a significant amount of money to try out their three products. If there were enough people interested that we could share, that could be something to explore.

Cheers,
Pat

_________________
There are three kinds of people:

Those that make things happen,
those that watch things happen,
and those that wondered what happened.

While you were responding, I shot what I hope will be the final coat on the top. But for a few nibs, I'd be tempted to slap a bridge on it and declare victory.

So, 3rd World shoots three light coats 5 minutes apart. Hmmm. Two light coats wouldn't sag and, if the wait allows the stuff to set up a bit, I can see how the third wouldn't either. Would have to ensure nothing dropped on the finish before the subsequent coat or it would be trapped. Well, I'm committed to the booth once I get more feedback on positive or negative pressure and the filter configuration. If this top buffs well, I'll know that I'm on the right track. If not, expect I'll be willing to participate in a group investigation.

Pat/Jeb et al,

I got talking to one of the Cardinal guys at the Healdsburg Guitar Festival. Not 100% sure it was "Cardinal" (it's the people LMI are going with shortly), plus I forget the guy's name right now, but I have his card somewhere, so I can dig that out later. He has worked at the "doing" end of the finishing business for 35 years. When I explained the problems we were seeing with our UV finishes (nibs and pits) he laughed and said the fix was easy! He was very helpful in general and said he'd be more than happy to answer any questions we may have in the future - I told him we'd definately take him up on his offer!

The nibs are caused by tiny bits of dust from the atmosphere landing on the wood prior to the finish being applied, and sometimes after the finish is applied - the fix is a clean room/booth, but we knew that already, right?! Time to build a booth!!

The big news (for me, anyway) is that the pits (little volcano-like holes that seem to go all the way down to the wood, so no amount of sanding gets them out) are caused by WATER in the compressed air. Apparently, teeny tiny amounts of water from the HVLP turbine or HVLP conversion gun air line get introduced into the finish and don't cause any issues until we use the UV lamp to cure the finish. Then, the heat from the UV lamp evaporates the water in a small puff of steam, at the same time the polyester finish cures, leaving a pit where the steam burst through the finish (just like an exploding volcano!)! I've actually seen these small puffs happening as I use my UV lamp - I thought that I was just too close to the finish and the puffs of "smoke" were just little bits of overheated finish. This explains why I've not had any pit issues when I brush the finish on - no water!!The fix is to put a water-remover (air dryer) inline with your HVLP gun. This isn't going to work with a turbine (real) HVLP - I've not ever seen any air dryers big enough (do they make them?), but it should be an easy fix for an HVLP conversion gun using off-the-shelf parts. I'm going to get an air dryer and give it a try at the weekend.

HTH,
Dave F.

_________________
Cambrian Guitars

"There goes Mister Tic-Tac out the back with some bric-brac from the knick-knack rack"

Dave your friend's got the right idea.
First, the air supply. Full time finishers, (like Joe) as well as automotive finishers have air line filters that cost a BUNCH. Maybe Joe can tell us exactly what filter he has, but I suspect it cost several hundred dollars. I've got a ~$40 water trap type filter at my compressor, and another inside my booth. I also use a disposable filter at my gun like this one. http://www.tcpglobal.com/spraygundepot/itemdetail.aspx?itemno=SHA+8100 I change the filter at the gun every couple guitars.

Reguarding dust. Super clean booth. I've got a BIG (explosion proof) fan, and a small booth. You need to filter the air entering the booth. I turn my fan on, full speed and blow out the entire booth with an air hose, and kinda let the fan suck all the airborne dust out before spraying. Wipe the guitar down with a tack cloth, or whatever method is approtiate with your finish. And there's one more....trick. Tyvek suit. My first several finishes, as well as a bunch of re finishes on factory guitars were Nitro. It seemed like I always had dust problems, reguardless of how good I cleaned everything up. I switched to (catalyzed) Polyester on my necks, and also done a few bodies with it. I never had any dust problems when using Polyester, even though Nitro dries dust free quicker than Polyester. For my safety I was using a Tyvek suit, and hooded respirator with Polyester. I finally figured out that dust off my clothes, and out of my hair was getting in the finish.

Pat, try thinning your finish. I don't know what thinner you'd need to use. Most Polyester finishes thin with MEK. Some will also thin with acetone, but I'm not sure about the Cure UV stuff. (Doesn't cure UV has some waterborne uv cured finishes???? Maybe thin with water????) If the finish has a thinner consistancy you'll be able to spray a thinner coat, without the orange peel or dry pebbly texture. Be sure and give it enough time for the thinner to off gas before curing with your light though. Manufacturers often ship finishes that are too thick, and recommend spraying as shipped to meet VOC standards. Check your film thickness. It may take an extra coat of 2 since the thinner finish won't build quite as fast.


Reguarding safety. Make sure you get the MSDS for whatever you're using. It will have all the information you need reguarding PPE, but can be hard to read. If needed I'd recommend taking your MSDS to a big automotive body shop, or automotive paint supplier and seeing if they have someone who can outline what safety equipment you need.

Be careful with those bright UV lights too.

_________________
I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

Yup, I figured the nibs were caused by pre-shoot dust on the surface cuz they largely disappeared with careful use of a tack cloth. Liberon ones seem to work well removing the dust and don't seem to cause problems. I've seen the puffs of steam too. Makes perfect sense. I have a water trap at the gun and at the tank but apparently there's a reason the pros don't rely on a $20 item. And I bet my bunny suit explains some of my improvement, as Woody suggests. Guess the suit should be part of the booth cleaning procedure before finishing.

I think that Woody makes a good point about thinning as well. The coat I shot earlier today didn't flow out perfectly even after 20 minutes. Still had a subtle orange peel or mottled look indicating a surface that isn't quite flat and that seems to cause the whole coat to refract light accordingly. It just won't come out with sanding, whether I use 2000 ANSI or P1200, before I go through that layer somewhere. Please tell me whether I'm interpreting my experience correctly.

If a booth and line drying will get rid of the contamination, and I/we can get this stuff to flow out better, we'll be in business. Still wonder whether another formulation will hang on a vertical surface better. Oh, well. First things first. Gonna start fixing up the finish room tomorrow; remove carpet, paint floor, weather-seal door. I think my space is well-suited to Dave Livermore's suggestion for a positive pressure booth. Hopefully he'll see my questions about filter panel and housing the fan. If you, Woody, or anyone else have thoughts on the matter, would love to hear 'em.

This has been a struggle but I guess if it were easy we wouldn't be making all this money. Uhh...spending all this money. Wish I were younger. :>)

Jeb

The only problem I see with a positive pressure booth............I'm lazy. My "use the fan to suck the dust out of the booth" method is really easy. Reguardless, be sure to filter the air entering your booth.

_________________
I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

Well look at it this way... if your fan is exhausting at a given CFM, you want the inflow to be capable of keeping up with it or you lose efficiency and the fumes and overspray aren't evacuated as they otherwise could be. I have no idea of the math there though.

Of course if you're evacuating air out of the house/shop, then you need to consider the need to provide replacement air. Meaning you need an open window or something so that you don't create a negative pressure environment that works against you.

_________________
"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."

A fun thing to try: go into a dark room with a flashlight. Hold the flashlight up to your temple pointing forward. Adjust until you can see the dust in the air. Now give your hair a tussle.... Makes you appreciate the hair nets that people preparing food wear.

Pat

_________________
There are three kinds of people:

Those that make things happen,
those that watch things happen,
and those that wondered what happened.

I suspect Joe and any other pro finishers are using a proper air dryer, like the one I have. It handles 18CFM @ 90PSI (the entire output of my compressor) and there's a filter inline that catches all the oil in the air. Without the dryer, the oil filter would get clogged up with water, so they're much more effective together. The dryer cost 20% more than the compressor, and they're both from the same industrial product line.



They're essentially very powerful dehumidifiers. They're got refrigeration units in them and they spray out the excess water every ten minutes or so at line pressure to make visitors to your shop jump

_________________
Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

I suspect Joe and any other pro finishers are using a proper air dryer, like the one I have.




Took your tip to heart, Bob, and found a refrigerated dryer on ebay to match my 10 CFM compressor for $400 new which is less than many of the more capable desiccant units. I will have more finish problems but I expect they won't be caused by water in the lines. Thanks! Spray booth is well underway...

Jeb