Official Luthiers Forum!

I was about to let this issue go but I honestly think people need to be made aware of this particular UV curing system. First let me state that I hope no one will question whether I was using the product correctly. I spent twenty years developing molding and finishing processes for my own manufactuing company. I followed their instructions to the letter on 6 test panels. In addition, I did an additional 28 discreet tests in which I isolated and progressively altered single variables. Lastly I did a series of controlled impact evaluations and compared that to tests panels finished conventioanlly with nitro.

I returned the system for three basic reasons:

1. The topcoat cannot be sprayed onto a complex surface without running. It is mariginally thixotropic...meaing it thins out under a shear load...like when it goes through a spray nozzle...but it needs to be far more so. It doesn't atomize well as a result. It's not psuedoplastic at all...meaning it will not thicken as it lays back out into a film when sprayed. So it runs very easiliy.

2. The handheld light will work for most situations but in order to acheive reliable cure I would have to use a large reflective booth....like the big companies do. Trying to get into the concave crevices of my electric guitars meant that the light would have to be held in that spot fro a few moments...but then the light is very close to other points on the guitar and the risk of burning the finish there is just too high to rely on this method. The booth they sell is $20,000.

3. The worst thing was the fact that the sealer never dries or cures. I became aware of this toward the end of my experiments when the sealer seeped all the way through a .2" test panel of mahogany. I took some pics of the problem and confered with CureUV.com about this and their reply was, "that's how it was designed". It was then I decided to return the system. This guitar sat for three months after having gone through the full CureUV.com system. I decided to sand it down yesterday. This morning I went out to my shop and saw this...which I expected.

I just thought I'd share the pic with you to let you know that if you are using this system you have liquid trapped under your topcoat...if using porous woods.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

Wow. I hope your guitar is not ruined. Thanks for the heads up on this product.

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http://www.CostaGuitars.com
PMoMC

I've got no comment on any of the UV systems people are using, but I'd recommend getting the isolante sealer from Chemcraft regardless of which topcoat you're using. Mike Collins (Selmer Mike Collins) has confirmed that you really can spray topcoat a very short time after spraying the sealer, which I believe is about 30 minutes. They say it's tack free in 15 minutes and sandable after 60.

I've experienced the joy of sanding off a product that didn't cure, myself, so the fact that the Chemcraft sealer is so eager to cure puts it on top of my list

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Bummer dude. I was planning on investigating cureUV as well but might cross it off the list unless they get this sorted out.

As to a save, I think with a good masking job, you could go full black on the center slab and it would be a pretty good looking guitar.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Oh....definitely look into other brands and systems. I know for a fact that many of them have solved the major issues with the topcoats. Several companies have developed their topcoats to allow for three coats to be stacked prior to curing....which means the psuedoplastic properties are developed and controlled. I would also assume that the sealer issues are more refined if the company has worked on their topcoat to this degree. This UVCure product strikes me as having been marketed by folks who haven't done that much finishing...on instruments..therefore it was marketed to luthiers prior to being truly useful for everyone.

When searching for a system ask very specifically, "Can you stack three wet topcoats before you cure it?" You'll be on a good track to success if only this one thing is resolved.

Companies like Paul Reed Smith and Taylor, who utilize UV cure systems have process engineers on staff that have worked out all these issues. Although CureUV.com likes to drop the names of PRS and Taylor, as they did with me when selling it, and also when defending their system when I wanted to return it, neither one of those companies are using their products as supplied in their kit. Both companies have spent a considerable amount of time and effort to develop their UV finishing processes.

I finished two guitars with this system. It remains to be seen whether they are both ruined by the eternally uncuring sealer but I was able to seemingly seal the material inside with shellac. The sealer seeps out from open pores but it gives you a bit of time before it shows on a freshly sanded surface. If shellac is applied immediately, the sealer doesn't seem to appear again. We'll see though. I can't send these two guitars to anyone for a while...that's certain. I'm very worried about adhesion in these areas.

"That's how it was desinged." Ya....right.

_________________
I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

Along the lines of what Bob said. A UV cured sealer sounds like a problem waiting to happen. The sealer will soak into places where the UV can't get, even with an expensive reflective booth. I suspect that if Taylor is using Cure UV finishes they're also using a catalyzed sealer, not a UV cured sealer.

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

Yep...I believe that very thing...though polyester is inert when fully cured so I don't know how they are getting a crosslink with the pore filling gel. Could be that they apply the pore gel when the catalyzed sealer is in the B stage during its cure cycle. In the B stage the film is partially cured and the surface molecules are receptive to crosslinking. I don't know if crosslink can occur between systems that are catalyzed differently. I do know that Taylor and PRS are certainly NOT using the CureUV products out of the box using their instructions. That's just nonsense.

There's no way Taylor is going to risk having a sealer flow through to the inside of their guitars...not a chance.

One of my experiments was an attmept to pre-seal the pores with shellac so that the uv sealer didn't flow further than the pore depth...which worked ok though adhesion did not improve (another minor issue with the UVCure.com system was less than optimal adhesion). Then I dropped the sealer entirely and used the pore filling gel directly over the shellac...which also sort of worked (with no adhesion improvement) but by that time I knew the topcoat and light issues would not be resolved so I was disenchanted by then.

_________________
I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

I suspect if Taylor, PRS ect are using Cure UV stuff it's their cabinets. Back when I knew what Taylor was using it was Mcfadden UV cured Polyester. They used Mcfaddens "Rosewood sealer" under it. I have no idea what they're using since Mcfadden is out of business r even how long they used it. I don't think the top coat actually burns into the sealer. Mcfadden recommends sanding the sealer with 200 grit. I suspect this was to key it for adhesion.

From Mcfaddens PDS sheet for UV cured Polyester

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

As many of you are aware, I have also been working my way up the learning curve with the finish from cureuv.com and have been slowly resolving the issues I've had. I feel I am getting close to being able to get consistent, decent results. What follows is in no way meant to be a critic of Zlurgh's comments, just my own thoughts to offer a different point of view for the benefit of the forum.

I have seen the phenomenon that Zlurgh has described in cases where I did not pore fill with the gel pore filler either initially or where I sanded back to bare wood but did not re-pore fill with the gel filler. It seemed to me that it was some of the top coat, not the sealer that had made it into the pores and not curing. I think it is related to the issue that was brought up in another thread that described how Solarz would not cure if it was applied very thin such as in a wipe on, wipe off method. I found the same with the cureuv top coat finish. If it is applied super thin, it won't cure. My other observation in support of this theory is that the sealer seems to dry well just in air as described in the instructions whereas the top coat will seemingly stay uncured forever if it isn't being cured by the light. My lesson was to make sure I did good pore filling with the gel filler.

As Zlurgh said, the finish does not apparently hang well and I can't seem to get it on thick enough to flow out but thin enough so that it doesn't run. My work-around has been to do one surface at a time. Sides are more of a challenge. With respect to curing something with the tight curves in a cutaway - just did it. Yes you have to vary your time and distance with the light to negotiate the curves and get an approximately even cure, but I didn't find it that difficult. I just don't see this as one of the bigger challenges associated with this finish method.

The work to finish a guitar with this is much more than I had anticipated - mainly due to all the sanding to remove nibs and get a surface ready to buff. Then you have to buff for a very long time to reach that "wet" look.

I will also say that the folks at cureuv really do need to get some better support going on and be less mis-leading. Despite what you may see on their web site, neither PRS or Micheal Greenfield use their finish product (they use their light). I don't think they get the fact that their reputation is taking a beating. They desperately need to get out the video they have promised to do with Third World Guitars (which is the only company I am aware of that state they are using this product successfully).

Finally, here is a picture of the back of a guitar I just re-finished using the cureuv product:

[img]<a%20href="http://s274.photobucket.com/albums/jj247/Pat_Hawley/?action=view&amp;current=P1020365.jpg"%20target="_blank"><img%20src="http://i274.photobucket.com/albums/jj247/Pat_Hawley/P1020365.jpg"%20border="0"%20alt="Luc's%20Guitar%20Back"></a>[/img]

This was brushed, not sprayed. It's getting there and despite the challenges, to me, the advantages offered by the system still make the pursuit worthwhile.


Pat

_________________
There are three kinds of people:

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

Let me try again to get the picture up:

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There are three kinds of people:

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

Ya....I would suggest the only way to apply the CureUV topcoat is by brushing it on. Furthermore....if the system is going to work at all it's going to work on things that have defined edges and flat surfaces....like the box of an acoustic guitar. Defined edges so you can do it in sections and flat surfaces so you can keep it level and it doesn't run off.

But trying to brush this particular topcoat onto a complex surface is basically hopeless.

The sealer is going to cure in some situations and has no chance in others. The variable is the porosity of the wood...best I can tell. I just need to say that there is no chance that it's uncured topcoat seeping around in that wood. I'm not being defensive, Pat...it's just I'm an anal retentive ex-engraver who could write the Lord's Prayer on the head of a pin. The supplied procedures were followed to the letter and it's not very hard to see when you've sanded through the gel/pore/fill coat in the right light...it basically pokes you in the eye....lol.

And, of course, when confronted with pictures of the seepage, CureUV.com admitted the sealer didn't cure...suggesting rather, that it was designed to be that way.

All that said though, Pat....that back looks very sharp. I got flat panels to do that...but never the face of my guitars. How did you handle the sides on that? Small sections at a time?

_________________
I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

Just an idea - what would happen if you waited until you had a decent amount of seepage and then hit it with the light? That might seal of the pores that have collected "sealant" so that it won't weep any more. Throw some shellac over that and hit it with opaque black.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Stu,

I will have to do some more experimenting with the sealer to see if I can replicate what you are getting with just sealer by itself. My experience has been that the sealer does seem to dry in 15 to 30 minutes but after all the issues I've had, I'm certainly open to the idea there's stuff I haven't noticed yet.

For the sides I had set up the guitar with a BBQ rotisserie to keep it moving while the finish leveled out. It didn't work perfectly so there was more sanding to do to level things out but I got there. Curved surfaces are the toughest but I have managed a few necks. I must admit, I'm not sure I want to attempt your style of guitars with this finish. It would be difficult to get a reasonably level surface to start with and you would have to follow up with a lot of careful sanding. It could be very frustrating indeed.

Omar at Third World Guitars sprays and claims to have no issues at all. He does all his surfaces with the guitar hanging and waits up to 20 minutes prior to curing. How he does this, I don't know but he has said I can visit his shop if I go to Florida. I may have to do that.

Pat

_________________
There are three kinds of people:

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

Taylor is not using CureUV. Many folks are using Simtech or Axon. And PRS is using an oven from SPDI.

SPDI is the parent company of cureuv.com

Pat

_________________
There are three kinds of people:

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