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In another thread I promised I would give some details about my quest to learn spraying UV finish, so here it goes...

At the end of 2018 / early 2019 I decided I was going to spend a solid year getting better at finishing my instruments. Like most I’ve tried a whole host of methods and materials. Some successful and some not so much. I was (and still am) convinced that my lack of success was because of jumping from finish to finish trying every option I read about online or watched on YouTube. Instead of giving any one option a real chance and learning the finer points I would bail out to the next thing.

Some things I have tried:

- French Polish - I had moderate success with the Tom Bills approach on two instruments ( I forget who taught Tom the method).

- Endurovar over zpoxy - This is what I did the most of prior to UV ( six instruments) and had decent results.

- Post cat Royal Lac (sprayed) - One experience, failed and removed from the instrument.

- Wipe on poly - It’s fine, but didn’t do it for me. I did two guitars, left one and sanded one back to wood to try something else.

- Tung oil on a couple ukes and one guitar.

All of these finishes (maybe with the exception of tung oil) can give a great finish. Like I said, I wasn’t sticking with anything long enough to really learn the skills needed to do it well.

So back to my year of learning to finish.... I had read some here and there about UV cured finishes and stumbled on Brian Howard’s blog about UV that he posted in November of 2018 - http://howardguitars.blogspot.com/2018/ ... s.html?m=1

At the end of the article Brian extended an invite to come spend time with him in his shop and learn about using the UV materials. I mulled it over, and decided I would try on my own first before taking any formal instruction (famous last words right).

I purchased the Cure Buddy system from UV3 - https://uv3.com/product/cure-buddy/

This system has worked really well for me. Simply following the instructions in Brian’s blog I was able to get started quickly and had some success with test panels. I made my own homemade version of the docking station which helps with giving a place to set the wand between coats. The UV bulb takes 10-20 minutes to fully warm up and the on/off cycles are limited to a few thousand and so leaving it on during the entire session minimizes the wear and tear on the bulb.





When using the curing wand you need protection. I use these long gloves and face shield that came with the unit. I also wear a long sleeve shirt. This is because my spray booth walls are all white (by design ) and I got a nice suntan on my arms from the light bouncing around the room.



For materials I’m using the UV topcoat and porefill from Simtec -

http://www1.inetba.com/simteccoatings/f ... nguide.htm

http://www1.inetba.com/simteccoatings/f ... cation.htm

And their two-part isolante (adhesion promoter) as a barrier coat:

http://www1.inetba.com/simteccoatings/f ... x1MSDS.htm



I use the Devilbiss SRI Pro gun with a 1mm fluid tip for the adhesion promoter and a 1.2mm tip for the UV top coat. I bought two of them used from Craigslist. They were not in great shape so I had to clean them up and replace the needle packing and fluid tips. Now they work great.



After trying test panels and one instrument I had moderate success but already could tell I was in need of some training. I follow the schedule laid out on Brian’s blog almost exactly the same. The only change is that I spray the entire body and then cure the entire body at one time.

In March of 19 (feels like two lifetimes ago) I went and spent a few days with Brian. He walked me through the process from surface prep to the buffer. It was immensely helpful to learn all the little tips and tricks and also to confirm which of my habits were good and which were bad. Brian is a great dude and if you have a chance to spend time with him I would recommend it.

I think one of the keys to good results is surface prep. That’s true for any finish but especially true here because the UV topcoat will find any hole or edge and build around it, it does not flow into it. Especially problematic for me is tiny pin holes or gaps in the binding / purfling on the top side of the instrument. The back has the porefill so hasn’t been an issue. Using the optivisor and dropping a bit of porefill into any imperfections I find has helped to work around this.

The number one thing I learned with Brian is that I was using sandpaper way, way past it’s usefulness. This leads to increase in pressure to get it to cut and ultimately sanding through. Seeing this in person, when Brian would swap out paper, was eye opening. Also listening to the paper cut. I had always gone by feel the same as a file. You can feel when a file is no longer cutting. It’s the same with sandpaper, but you can also listen and hear it change from cutting to gliding.

To prevent myself from being tempted to use paper too long I now cut it all up in advance and set it out. That way I don’t have to stop and rip a sheet up. I can stay in the zone, such as it is.

Here is a uke with 400 - 2K pieces of 1/16th sheet of paper.



The process is basically:

- Spray adhesion promoter using a 1mm fluid tip. I do 2-3 coats 30 minutes apart. This is very thin. .5 - 1 mils. After curing scuff with 220.

- Porefill with the UV cured porefill. This is a jelly that is spread on about like epoxy. Usually takes 2-3 sessions. You don’t want to glob this stuff on cause it’s tough as nails and takes forever to sand back. I do the first coat with a spreader and the second (third) with a paper towel. Scuff and cure each coat in between and sanding with 220 to level it.

- Spray first top coats. For this I spray around 2mils per coat, two coats waiting 20 minutes between coats. Then cure. Brian has put a nice visualization of the curing pattern on his blog, that helps to ensure everything is fully cured. Scuff with 220.

- Spray the last two top coats and cure as before. Then sand 400 to about 75% or so level and then work up the grits. I go 400, 600, 800, 1200, 1500, 2K. All dry sanding.

- Buffing is with the SM buffer and Menzerna compounds.

Here are some results. I can go from surface prep to buffer in a weekend, but it’s a long weekend. What I prefer to do instead is give the finish a day after curing and then level / buff a day or two later.



















Hopefully some of that is useful. I’m happy to answer questions if I know the answers.

Brad


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Brad, thanks for walking us through your experience with this.
Your results really speak for themselves - they look sensational. How much do you think you have invested in this now ($ and hours) to get such a great outcome? It looks like it has lifted your building to a whole new level and I am very jealous. But I am guessing that someone like me building a couple of instruments a year as a hobby is not going to be able to get into this?

Really fine looking end result you are getting there Brad.
What final thickness are you getting?
I'll echo Marks query on investment $-wise for kit, and also for materials to finish per guitar, roughly?
EDIT got a warning on the cure kit link from Norton
"Dangerous Webpage Blocked You attempted to access:https://uv3.com/product/cure-buddy/This is a known dangerous webpage. It is highly recommended that you do NOT visit this page."
Not getting that on a google search result - but still getting it inside the site itself - ?
Ouch on the price! $2,395.00, for the starter set, quite an investment, but you're getting the results.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Thanks, Colin. I let them know about the UV3 site. I’m not affiliated or anything, they have just treated me well.

There is a more cost effective unit on their site now that is $1400 that is intended for hobbyist. That option wasn’t available when I ordered mine.

The Simtec materials and cost is roughly:

37X6 UV Cure Topcoat 1 quart $ 30.00 1 gallon $93.50
59X1 UV Cure Pore filler 1 quart $ 32.00 1 Gallon $ 95.50
58X1 And 58X1 Adhesion promoter $ 24.50 Per quart.

I have a quart of the porefill and used maybe 30% of it so far, but that’s with 5 instruments and lots of test panels and a couple of mock up bodies that used several times each while learning.

The cost to get started is for sure high. I’m not necessarily trying to turn to selling my instruments anytime soon although that is a long term goal for sure. I should be clear that I went down this path for a number of reasons:

- I’m a bit nerdy and the gear was enticing.
- The ability to get good results in a condensed timeframe.
- Lower VOC than Nitro, etc.. since I’m spraying at home.

It’s not solvent free though, I do have to add about 5-10% solvent to it. But it’s high solids so takes very few coats. 4 is what I’ve been spraying per Brian’s blog.

The final film thickness is ~4-5 mils. I’m measuring it at the bridge footprint and fretboard extension footprint after routing them off. Following the same schedule of coats on each instrument they’ve all been in that range.

Brad





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I really appreciate you showing us this detail, Brad. The instrument finishes you are getting look fantastic!

The most obvious differentiating factors for UV cure versus the other spray finishes you have tried are the faster cure times at each stage, and the cost of the light source. Setting those two factors aside, do you feel you are getting a better finish in ways that cannot be duplicated with other finishing methods, or do you feel that the other sprayed finishes you have used could be as good as your current finish, with enough work (and putting up with longer cure time)?

I would love the faster cure time, but not the extra cost of the light source. I’m in the middle of setting up a spray booth so that I can move from hand finishing to spray finishing. Your info is very helpful. Thanks!

Hi Mark,

The cost (roughly) I put in the above reply. It’s certainly an investment, even with the now less expensive lamp offered from UV3.

In terms of hours, I would hazard a guess that I’ve spent at least 300 hours over the last year and a half doing test panels and bodies. I mocked up an EIR and mahogany body, 00 sized, and went all the way to the buffing stage on them a few times each. I was experimenting with using a ROS vs hand sanding, using scotchbrite, etc.... to see how it affected the outcome. I know it sounds like a moment, but really cycling paper more frequently was key for me.

Also, this stuff is tough as nails. I was using 80 grit on a ROS to take the test bodies back to wood and it still took forever (and was seriously messy!). I was able to do each test body a couple times before I sanded holes in the top. The last test cycle it was like refinishing Willie’s guitar, Trigger.


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Thanks, Don.

First I’ll say, if it isn’t obvious already, I’m not an expert in really any aspect of finishing. What I can say is that there are lots of guitars and lots of finishing methods on display on Instagram and many of them look fantastic. I would expect, given the focus and investment in time that I gave UV, a builder could have the same success with other materials. Seeing all the beauties here on the OLF makes me 100% sure of that.

The time to cure is certainly a differentiating factor. Another factor is the durability of the UV material. It seems to be really very durable. But honestly the thing I like about it the most is that water clear depth that I couldn’t get until now. I’ve never sprayed Nitro, but I understand that you can get that same clarity with it. I see it in instruments all the time that were finished with it. So that could be a differentiator. Getting that clear deep finish with a lower VOC material. The depth and clarity of the finish is really impressive to my eyes.

Brad

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Great write up Brad. I wish that stuff wasn't so expensive as I would love to give it a try. Especially for clients who want road worthy instruments with strong finishes.

Have you done any experiments with tone? I know this is next to impossible to do but intuitively do you hear anything different about the various finishes you have used and the UV?

Thanks for the write up, very interesting.

Thanks, John.

I do worry about tone because of some reports that UV negatively affected the tone. Even here on the OLF from I think Ed on some of his Halcyon guitars? This is an area where I’m severely hampered to make an informed statement. I’m not a great player, I have bad tinnitus and I didn’t start playing guitar at all until about 7 years ago. The trifecta!! So I don’t have that deep rich history many players or builders have with experience across a wide range of styles of instruments. I’ve made a conscious effort to try to play as many instruments as I can get my hands on though.

What I can give is just my experience. I haven’t noticed any effects in tone on the few I’ve built that I would attribute to differences in finish material alone. I have a few D sized builds but they’re not scalloped bracing so I cannot easily compare them to the Martin D’s I have access to, which I believe are all scalloped. To me though, they pretty much sound like a dred.

Brad



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Thanks for taking the time to share the process, Brad. Extremely interesting!


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Polyester does affect tone fellas. I believe it does lessen the potential of your guitars but by no means at all is this a massive detraction. If you can apply a super thin polyester finish then you can still create an incredible guitar and there is the tremendous benefit of durability and chemical resistance that no other finish can duplicate.

If you are aiming for squeezing every ounce of tone you can out of your guitar, then I can tell you that both French Polish and oil varnish are without question, superior to polyester. Bear in mind, that I'm building at the highest level with guitars that are extremely responsive and vibrant. I doubt a factory guitar would see any difference between thinly applied finish types - but there is a reason you don't see polyester applied on a good classical top as it would destroy the tone. For a classical top, I would probably only use French Polish as you can get the finish on so incredibly thin. I can discern no difference between pre and post finish response of my steel string bodies with oil varnish and French Polish. Polyester always deadened the sound slightly.

I am currently in the process of trying out nitrocellulose lacquer and my discussions with a few top builders recently has given me hope that I will be able to get the same tone from a super thin nitro finish. Applying the finish thin is very important and my initial impression is very good.

I've also spoken with a well-regarded luthier that uses McFadden's urethane. I believe this is the same thing Goodall is using now as well. Tonally, he feels that it is a very good choice if applied thinly. Urethane is quite a bit harder than nitro but nowhere close to polyester. I really do believe that the more "delicate" finishes are better tonal options. Every finish type has advantages and disadvantages and there is no wrong answer so long as you apply the finish thinly.

Personally, I'm glad I chose polyester finish for the first 15 years of my build career. It is only until the past several years that I feel my work is at that level where there just isn't much else I can do to make them any better. I want a hair more openness, responsiveness, and warmth while still keeping everything else my guitars have -- just using a French Polish top does that for me, which is why I'm opting for the more delicate finishes.

Also, forgot to say -- Very nice work, Brad !!!!

Try to keep the polyester under 3 mils everywhere on the top. Ideally, make it 2mils or under but that is definitely more challenging. If you can, then the finish is really not going to effect the tone that much. If you can do a nice polyester finish, you also might look at urethane. It is much easier to buff and will probably have a lesser effect on the tone if your film thickness isn't super thin.

Thanks!

This is very useful feedback (both replies). I will do some experimentation with trying to get the top thinner. The last few I’ve done the finish is 4 mils at the center of the bridge and ~ 5 at the wings. I can try one less coat on the top. With some careful preparation it should be OK.

I also wonder if I’m getting a 100% true reading. I’m measuring the finish after routing off the bridge footprint. I wouldn’t be shocked if my measurements are +/- a mil or more from measuring that way? What’s the best way to get a good accurate reading?

I’ve also considered not doing the adhesion promoter on the top. The two guitars I just finished had wood rosettes of EIR and cocobolo so I didn’t want to skip it on those. Perhaps I can mask off and spray just the rosette or paint it on or something. Will try a few tests.

I truly do appreciate the feedback.

Brad


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With any coating that doesn't burn in (basically, lacquer and shellac), getting a super thin coating can be challenging because of witness lines. Brian H might be the best guy to talk to regarding some tips with the polyester. I'm also considering the McFadden's urethane but those experiments are probably a few years out.

A good way to test thickness is to chisel off the finish underneath the bridge. You can also use frisket tape as a benchmark of sorts in terms of thickness.

Once you run out of your polyester - you might try the urethane. I imagine that if you can do a good polyester, then the urethane will be much easier and I'd think most of the same skills and process will carryover. I've buffed polyester before and it isn't a fun thing to do.

Thanks, you’ve given me a lot to think about.

Technically, I think I can wet stack three coats and cure all three at the same time. I could think about doing this just for the top alone and still doing the two -> cure / scuff -> two on the back and sides. I might have to mock up another body for some tests.

Brad


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These are the only ones that DO burn in.

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Hutch

Get the heck off the couch and go build a guitar!!!!

Hi Banjo,
Yes, that's what I was intending to convey by putting the parentheses right after "burn in". Granted, that wasn't the clearest way to state that sentence - but I'm fairly dumb and don't do no good at grammar and stuff ...

Gdang.

Just accidentally erased a detailed reply which I haven’t the gumph to redo.

Summary, didn’t work for me, ymmv especially if you can reduce film thickness.

Urethane at same film thickness significantly better sounding.

Some people make fine guitars with it so you prolly can too, if you figure how to accommodate it.

It’s the one finish Gore recommends to avoid, he’s right about lots of stuff...

Thanks, Ed. I had recalled reading your comments in previous threads and value your opinion.

For now I will focus on getting what I have as thin as possible, I have a gallon of the material. I will look into urethane as you and Toonces (sorry, don’t know your real name ) recommended.

Truth be told, I’m surely not building such a lightly built / responsive guitar that it matters which finish I use. I will get there eventually.

Brad


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Hi Brad,
My real name is Simon Fay. I've been building guitars full-time for about 12-13 years now. If you are happy with the polyester, don't let us deter you from continuing to use it -- but maybe check out the urethane and see if you like it better. Again, you can build a superb guitar with the polyester. And if you ever do try the urethane - let everybody know what you think.

Nice to meet you, Simon.

Yes, I plan to continue on, but will work hard to make the materials I’m using the best they can be. You guys have given me good food for thought. I will certainly evaluate the urethane at some point.

I do want to say I appreciate the feedback and comments from all. This is what makes the OLF a great place. On Facebook I would have been flamed by some guy who has built exactly one instrument and sprayed nitro from a rattle can. I would get a lecture about the rich history of nitrocellulose lacquer and the many world class instruments that use it, including his one.

Anyway, take care. I’m working on a new uke and dred both in ziricote. Should be fun!

Brad


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Brad, what is that other box with the fan on top?

NM, its a docking station. I see they offer one for $275. Is it cooled like yours?

How much level sanding do you u have to do after application? I assume there is only one application.

The wand has a fan on the back of it that kicks on and off automatically via the power box. This pic was taken under the welding mask. You can see the fan, it blows are into the back of the wand to cool the bulb.



The other fan is for a “docking station” which I made using sheet metal, a microwave filter, and a fan from Amazon. The docking station from UV3 is like 250 or so, I made that thing in an hour with 30 bucks worth of parts. It’s the thing on the right.



Brad


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Our posts crossed streams.

Right, it’s a docking station that draws air out of the box. So basically the wand sits on top and it’s fan blows air into the box and the docking station fan draws it out. It’s not necessary to have the docking station. If you have a place to hang the wand that’s fine too.

That’s right, you level only at the end. Scuff between coats. You can wet stack coats and then cure them at one time. Brian recommends no more than two at a time. Simtec says you can stack more, but I haven’t experimented with that too much. I’m going to try stacking three coats on the top as a single session and see what final film I get. It might be closer to the 3mils that Simon mentioned being more in line with a “thin” application.

Brad



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