Official Luthiers Forum!

I've been working with a local luthier by the name of Greg German who builds archtop guitars, and he has been finishing instruments with the new UV Cured finish that so many builders are moving to. He said that he will offer finishing to other builders for a fee. He is located in Denver, CO by the way. Anyway, to meet him and see his setup and explaination about the finish, go to the link below. The only draw back is that he doesn't do much finish work in the winter becuase he is not set up with heat in the winter. But on warm days he could do spray. Anyway, just thought I'd pass this on for anyone looking for a UV cured finish. His website is HERE

Look at the video titled UV finish...
LuthiersSoundstage

Tracy

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Tracy
http://www.luthiersuppliers.com

Direct Link?

Dummy can't find it...

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http://www.dickeyguitars.com

Bruce,
I know some people have had problems displaying this page if they are using an Apple Safari browser, but I know it works well with IE 7.0. The video does not have a direct link because it is copyrighted. The developer used MS Silverlight do convert the video. Here is a screen shot:


Sorry I can't help you Bruce. But basically he shows you the spray booth and light used to cure the finish, and talks about the benefits if a UV finish...very hard, no yellowing, super thin, and can spray, level and buff all in the same day! He used to spray lacquer, but now he only does UV. I've seen his work and it is perfect!
Tracy

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Tracy
http://www.luthiersuppliers.com

I had no problems going to the link with Firefox..then again I have a fair amount of addons already embedded in my version...

Hey pretty cool. I need me one of those light bulbs for home land security. Burglar comes into the house, don the protective gear and let him have it!

I had to download Microsoft Silverlight software before viewing, and hey, the sound works, unlike YouTube now on my system.

Many good wishes on the new business venture!

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http://www.dickeyguitars.com

Stinking dialup! I miss being able to check out cool stuff like that. With dialup, I'm pretty limited to what I can grab on the net. The price you pay for livin' in the sticks I guess!

While a great deal has been made about UV, most of the same benefits can be had with polyurethane and polyester finishes that are catalyst cured.   The only significant difference is that it's a 24 hour cure rather than a one minute cure.   There is some anecdotal evidence that catalyst cured polyester is actually a tiny bit harder.   Those are the only differences. You can get the same film thickness, same no-yellowing qualities, etc. without the expense of the UV cure booth.   It was Bob Taylor, the king of UV, who talked me out of it...

Joe,
Sorry about the dialup, but I bet your scenery is much better than mine


Rick,
All points very well taken and thanks for that great information. However,
it was my understanding that the catalyzed Polyurethane's do shrink back
a little. I think the UV finish doesn't shrink, but I could be wrong. But
regardless of that, if I was a finisher, imagine how many more guitars I
could finish in a day with a 1 min cure time? I'm not stating UV is better
are harder, but just that I know someone who is now offering a UV finish
at pretty much the same price as lacquer or Poly. Just another option for
guitar builders who farm out the finish work. If I ever built a guitar that
was worth the cost of the finish, I'd go to Greg for the finish.   

Tracy

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Tracy
http://www.luthiersuppliers.com

    I have to say that rick is exactly right here. The catalyzed polyester is ever so slightly harder than the UV cure polyester finish.

    I use the UV cured stuff because I have the cool UV light and protective gear. Otherwise, I'd jump to the cat/poly finish.

    The light is a significant investment and has a fairly high maintenance cost with bulbs for replacement costing a few hundred dollars for the correct wavelength and quality.

   I love the look of my UV cured finishes, but if you've ever seen the work that Rick does on his guitars, you'll love the results that are possible with the catalyzed material just as much.

   As much as I really like the technology and the equipment, I would recommend that anyone considering a jump to a polyester finish check out the catalyzed version first....and always rent a light to try out the UV cured stuff before making a financial commitment to it.

   The UV light is exceptionally dangerous and can, quite literally, kill you if you don't take the proper precautions when using it.

Regards,
Kevin Gallagher/Omega Guitars

The more options that we have at anything, the better.

There is no shrink-back with catalyzed polyester.   I don't know where that myth comes from.   If you see any pore shrinkage with polyester finishes, it's what's under the poly.   Now that I'm pore filling with epoxy, there is no issue.   The acoustic I showed at Healdsburg last summer has a finish that I started on the Monday before the show...I rubbed it out and set the guitar up on Thursday, showed it on Friday, and there is still no sign of pore shrinkage on it.   

So if you really need a three day finish instead of four...spend the dough on UV.   You'll still need to pore fill and if you use rosewood, you'll have to shoot some sort of isolator coats.   This idea that UV gives you a one day finish is just bull.   

The chief advantage as I now see it is that when shooting a lot of guitars, you don't have to mix in cobalt and catalyst; you can shoot stuff from a 55 gallon drum through an airless rig.   

A lot of you are being seduced by razzle-dazzle that in fact saves very little time and costs a lot of dough.   

Bob Taylor didn't figure there was a payoff on UV until you were doing at least 100 guitars a month...

Rick, does the cobalt ever give a blue cast to the finish?

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http://www.chassonguitars.com

Rick, I'm not using a pore filler at all. Seal, and shoot the topcoats. I found, perhaps even by accident, that thinning it further than necessary to spray, allows it to flow nicely into the pores and it sets up on the first coat.

I now try to buff the following day after shooting because I find it a tad easier and faster to buff, and still no pore shrinkage, and if there's a nicer, clearer, glossier finish, I haven't seen it..  In fact, and I swear this is true, with the Chemcraft polyester, I can sand it back at about the 6 hour mark. I haven't tried buffing it then, as my day is over with, but it sands just nicely.

It -is- a one-day finish for me. The Chemcraft sealer also cuts a full day out of the schedule, since I can topcoat it after 20 minutes, no scuffing necessary. 20-25 minutes between topcoats. I've been on it now for nearly a year, and not a single issue has cropped up. It's everything th McFadden's is, and then some. Even in the can, it's clearer.

The only advantage with UV I can think of is the mixing and gun cleaning in between coats.

Kent, the cobalt does make the finish blue-ish, until you mix-in the MEKP, and apply it.  It's quite neutral at that point.

I've kept a chunk of cured finish, from the bottom of a mixing cup, that was over an inch thick. It cured sort of a blue-green, but after a year, turned almost perfectly clear, a touch amber.

So, no, no bluish cast.

Grumpy,
   I'm doing something very similar to your process with the UV poly finish. I found that the UV cured filler was trouble looking for a place to happen at times and it led me into a series of experiments with the top coat being allowed to act as a filler.

    I have really pushed the limits of my sealer/isolation coat by applying topcoats over it at different intervals of dry and cure for it and curing them to watch what happens with it. I've found that 5-6 hour is about the minimum dry/cure time that I can allow before spraying and curing UV topcoats over it so it can all fall into place in a nice long day in the shop.

    I shoot a pair of light coats and cure and those will more than sufficiently level as a filler. They are sanded and followed by my initial topcoats that will be leveled and sanded to provide a good mechanical bond between them and the final coats.

   In my case, too, a one day finish is well within reason with no shrinkage using this method. I've finished guitars in a day, but don't like to simply because I like to move around in the shop rather than spending it all in the spray/cure booth and at the downdraft tables.

   I agree with Rick, though, that the poly finish exhibits no shrinkage in itself. Anytime pore dropping and shrinkage are evident on a guitar finished with it, the problem is in whatever is under the polyester topcoats.

Regards,
Kevin Gallagher/Omega Guitars

sealer/isolation coat by applying topcoats over it at different
intervals of dry and cure for it and curing them to watch what happens
with it. I've found that 5-6 hour is about the minimum dry/cure time
that I can allow before spraying

With the McFadden's sealer, correct? They recommend 24hrs.

  Chemcraft's "Isolante" can be topped in 20 minutes. I asked for clarification a few times after I was told, and the fella just laughed, and said yes, 20 minutes. No issues at all, and it is dry to the touch at 20 minutes. So the sealer just becomes another coat, in the process, as they all are about 20-25 minutes apart. From prep time for the sealer to the last topcoat in under 2 hrs. total.

I try t get it all done in a day because it ties up my entire shop. In the cold months(-28 right now and shooting for -32 tonight!), there's no way I can keep the blower on all the time, so I shut down the blower right after spraying, and exit the whole shop. return for the next coat, and leave again right after.  After the final coat, I just go back and check on stuff and hit the blower for a couple minutes, every hour or so. So, if i had to stretch it out over a few days, it would be  a major bummer... This way, It's just a short morning and then a, mostly, day off. <bg>

Grumpy,

    28 degrees below and heading for 32 below? Wow!

    I'm going to give the Chemcraft Isolante a try under my topcoats. Even though MacFadden recommends 24 hours, I've had good results spraying ove their sealer/isolation coat in much less time.

    20 minutes sounds even better to me, though. Thanks for sharing.

Regards,
Kevin Gallagher/Omega Guitars

heading for 32 below? Wow!

methinks we'll dip even lower. from the last post to now, we've gone from -28.6 to -30.

Here's my handy dandy power monitor and thermometer.

Oh, it's Celcius, but still cold in any language <g> It's around -22 F...

Ultimately it's not the specific cure method that these new finishes are all about...that's just cross-linking throught oxydation, and it can be accomplished several ways... rather, it's the underlying chemistry that makes the "poly" finishes so good, and the slowest we're dealing with is still five times faster than a decent nitro lacquer job, and yields (in the opinion of some of us) a superior finish.

Yes, the cobalt adds a bit of blue tint.   I squirt in a few drops of US Cellulose MEK yellow dye to warm it up, and get a very nice subtle amber tint.   

Great information everyone, and thanks for sharing Mario. Not that I'll
ever
be spraying with this stuff, but many others will gather and use this
information. Great thread guys!

This is information from Greg directly:
Luthiers-
I'm now set up to do freelance finishing if any of you are in the market
for someone to do your spraying.
I exclusively use McFadden's UV cured polyester finish, which is the
same product used by Kevin Ryan, Taylor Guitars, etc. The finish is
probably 10x harder than nitrocellulose lacquer, it doesn't shrink or
yellow, and I've been getting great results at about 0.004" thick. It's
also environmentally friendly: 90% solids (as opposed to 25% solids for
nitro), virtually no VOC's, not explosive, much less harmful to the
luthier doing the spraying.

I'll spray a typical acoustic guitar for ~$375. A few bevels and extra
edges won't change the price, but many tight edges (F-style mandolins
and the like) will cost more.
Tracy

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Tracy
http://www.luthiersuppliers.com

Yeah, that's McFadden polyester...same stuff I use, but mine comes without the UV initiator, and I kick it with MEKP. It can also be dual cured...Tom Anderson does that to get the quick UV and then the slower harder cure with the MEKP.

The finish is
probably 10x harder than nitrocellulose lacquer

oooh, I hates that when someone says that....

Tougher, yes, harder, no.

Does anyone know how the film tech folks define and measure toughness and hardness? Can we assume that scratch resistance : toughness :: dent resistance : hardness?

I'm familiar with hardness measurements (Durometer) for materials but I'm not familiar with instruments nor procedures for measuring scratch resistance.

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JJ
Napa, CA
http://www.DonohueGuitars.com

JJ,
   With a durometer, the testers measure the hardness of a finish applied to a very hard surface that will not give so that the finish can be pressed to several different points of falure. One would be the ability for the durometer to dent or press it thin. Another is the pressure necessary to aplit the finish or crack it under the durometer stylus.

   Grumpy is exactly right and I've been guilty of saying harder in the case of comparing these polyester finishes to nitrocellulose lacquer. They are multiple times tougher or more durable, but not so much harder.

   Another way that testers look at finish durability is to measure its ability to flex and to expand and contract as a skin before it breaks or checks. There are many ways to check these characteristics of any finish and, as builders of guitars, we give any finish a run for its money as we spray it over broad flattish surfaces that provide a very flexible and mobile substrate as they expand and contract with changes in their ambient environment.

Regards,
Kevin Gallagher/Omega Guitars

   

This is great info gents, thank you very much!

I have a question about the sealer that Mario mentioned (Chemcraft)will it work over/on all woods, if I remember correctly there were some issues with some sealers over rosewood, if this one works over any wood then I'm ready to try it on a cocobolo guitar, if not, sounds like epoxy might work.

Greg

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Gwaltney Guitars