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 Post subject: UV cured finish update
PostPosted: Fri Jul 19, 2019 10:06 am 
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Brazilian Rosewood
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For those of you already into these finishes and those of you thinking about using them. Here is a comparison that illustrates how different these materials can be and how there is a formulation that will work for you no matter your preferences.
https://howardguitars.blogspot.com/2019/07/uv-cured-finishes-differences-in.html

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These users thanked the author B. Howard for the post (total 4): Durero (Tue Jul 23, 2019 1:05 pm) • bcombs510 (Fri Jul 19, 2019 11:29 am) • Clay S. (Fri Jul 19, 2019 11:04 am) • bftobin (Fri Jul 19, 2019 10:29 am)
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PostPosted: Sun Jul 21, 2019 1:53 pm 
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Great article Brian, Thanks for posting. For me I might try a 2K finish latter this year.

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PostPosted: Sun Jul 21, 2019 5:52 pm 
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Koa
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I've had a love it/hate it relationship going on with the Cureuv stuff for several years now. As you discuss in your article, it does not hang well on vertical surfaces. However, what works for me, and has turned out to be a game changer, is building up to a required thickness by doing partial cures. I spray on a coating, expose it to the light just long enough so it doesn't sag and then spray on the next coat. I do this five or six times before doing a final full cure. With this approach, spraying the guitar is quite a quick process - about 30 minutes to get all the coats completed. From there I go to sanding and buffing.

Cheers,
Pat
PS I will add that the single most important thing I learned about the cureuv stuff is to do five or six coats of the sealer/adhesion enhancer before going near the wood with the uv pore filler or top coat. This is required to prevent the uv finish from wicking into pores and/or end grain where it will not get cured. Later, it will weep out and make for blotchy looking pores.

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PostPosted: Mon Jul 22, 2019 5:49 am 
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Brazilian Rosewood
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Pat Hawley wrote:
I've had a love it/hate it relationship going on with the Cureuv stuff for several years now. As you discuss in your article, it does not hang well on vertical surfaces. However, what works for me, and has turned out to be a game changer, is building up to a required thickness by doing partial cures. I spray on a coating, expose it to the light just long enough so it doesn't sag and then spray on the next coat. I do this five or six times before doing a final full cure. With this approach, spraying the guitar is quite a quick process - about 30 minutes to get all the coats completed. From there I go to sanding and buffing.

Cheers,
Pat
PS I will add that the single most important thing I learned about the cureuv stuff is to do five or six coats of the sealer/adhesion enhancer before going near the wood with the uv pore filler or top coat. This is required to prevent the uv finish from wicking into pores and/or end grain where it will not get cured. Later, it will weep out and make for blotchy looking pores.



I have just started using their wipe on UV cured isolante or adhesion promoter. I agree it does not seal quite as well as the stand alone 2 part isolante from others but the advantage of good shelf life and ease of application make it a winner so far. I haven't noticed any real bleed through or absorption but based on your words I am going to run some tests.

I have heard of this partial cure before, maybe it was you? I may investigate this some as well but I have a few questions. What light set up are you using? Approximate exposure times? What is your actual coating weight per coat?

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https://www.howardguitarsdelaware.com/


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PostPosted: Mon Jul 22, 2019 7:59 pm 
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Koa
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I think I have mentioned the partial cure approach once or perhaps twice at the most. It's worth giving a try on a test board. I have one of the older 1100 series hand held lights from Cureuv.com. I don't think they sell this particular light any longer. It seems to work fine. To do a full cure I pass the light over the guitar relatively slowly twice. By slowly I'd say I'm moving my hand at about 2"/s. To do a partial cure I'm going at about twice that speed only once. After that it is still easy to smear with a finger but it doesn't droop. There seems to be a fairly generous window of speeds for doing the partial cures. I'm sorry, I don't know the actual coating weight per coat. All I can tell you is that by necessity with this stuff, I put on relatively thin coats. Aside from it not hanging well, it tends to back away from edges so if you put it on too thick, you end up with hills close to the edges that must be sanded out. Putting a radius on the guitar edges helps with this. I can also tell you that I use a mini HVLP air gun and after I am done my 5 - 7 coats, most of one reservoir that came with the air gun will have been used for a guitar body. By the time I am done sanding, based on crude measurements using a caliper, my finishes seem to be around 3 mil.

Please trust me and/or do some tests on the bleed through in order to save yourself some heartache. I was advised by the people at Cureuv.com that only one or two coats of the adhesion enhancer were required. Big mistake. Perhaps only one or two are required to get the adhesion, but 5 or 6 are required to get the sealing that you need on deep pores or end grain mahogany. And if the uv stuff (either the pore filler or the top coat) get to where it can't be cured by the light, it's a real problem. To that end, I pore fill very carefully making sure to leave no ridges that must be sanded out because I fear sanding through the sealer (my fears are well justified). Instead of sanding, I rough up the surface of the pore filler with a green scotch brite pad only prior to starting the top coats. It works well and I've never gone through the sealer with it. Once I figured this all out, I was happy with the sealer because, as you say, it's very easy to apply and dries so fast that putting on 5 or 6 coats is no problem.

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PostPosted: Tue Jul 23, 2019 6:47 am 
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Brazilian Rosewood
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Pat Hawley wrote:
. And if the uv stuff (either the pore filler or the top coat) get to where it can't be cured by the light, it's a real problem. To that end, I pore fill very carefully making sure to leave no ridges that must be sanded out because I fear sanding through the sealer (my fears are well justified)..



That is why Hentzen pushes the dual cure for the pore filler, Taylor had may problems with uncured filler....,But that adds new problems that to me are worse than the one we are fixing. Also why I do the 4 pass cure pattern every time.

as for the isolator I have used it so far on rosewood and mahogany at a single wipe on heavy/ wipe back of in 30 seconds application without any noticeable issues. I even re seal any sand throughs when pore filling with a quick wipe and have had no issues other than it doesn't seem to quite seal the oil in the rosewood ass well as the 2 part stuff Which that and you comments will have me doing at least double coats on oily woods. Got a mahogany guitar finishing up this AM and I'm gonna look over the whole thing with a loupe!

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You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/


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PostPosted: Tue Jul 23, 2019 10:37 am 
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Koa
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I hope you have no issues but I'm sorry to say that with only one coat of the isolator, I think there is a good chance that you will. In the event that you see the pores or end grain no longer looking "crisp" you will know that some of the uv filler or top coat got deep into the wood and didn't get cured. It is now bleeding back out of the pores under the finish that did cure. The best, but not perfect, solution I found to this problem was to sand right back to the wood to sand off the bleed out and re-apply isolator quickly to try and lock-in whatever un-cured finish is still deep in the wood. Alas, even then I have found that over time, the pores will again start to look fuzzy. These problems were eliminated entirely on subsequent guitars with up-front multiple coats of the isolator.

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


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