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Ready to start lacquer on my fourth guitar. The first two showed problems in the lacquer around seams/glue joints after close to a year of playing. Been playing #3 for almost two years, and it is beginning to feel rough in similar places. All three were glued with titebond orig, pore filled w Z-poxy, and then I can't remember how well I covered with the single coat of StewMac vinyl sealer before the cardinal lacquer (and on #2, I don't think I used a sealer at all).

So on #4, (after getting online very helpful advice from this group) I'm using the LMI glue that's supposed to be UV visible, Pore filling with the West Systems epoxy, and plan to spray a couple/few coats of Cardianal Vinyl Sealer before lacquer.

But I have a few questions:
1, Should I thin the vinyl sealer to 50% (LMI finish notes). I usually use 20% with a few % retarder for the lacquer. How many coats?
2. At one time I had a recommendation for a better spray gun in the 400 range, but I can't find it. Appreciate any recommendation.

Roy

blushing happens when you lock moisture in the finish , so be aware of humidity. I don't use vinyl anymore I use shellac flakes. I only use 1 coat as sealer is just that. I don't use epoxy I like aqua coat but be sure to follow the manufacturers advice.
When using any filler be aware that some fillers will look cloudy so do your prep well.
Using nitro I do thin the nitro and do not put on thick. Light coats are better than heavy.

thinning
I mix my thinner with a touch of retarder if humidity is above 50%
8oz thinner 1 oz retarder
many use too much retarder

thin mix 35 to 50% you have to find that for your area. I would suggest to start with a 50% mix , then do
a 40% and then 30%. See what works best for you.

Often they tell you allow 1 hr between coats I do 2 hr and place some tape under your fret board extension
measure your coverage after 4 coats. you want .008 to .0012 green coats. After a bit that shrinks more than
you may think.

if you do get blush you can use everclear and spray that lightly to allow moisture out. I have found most times
the cloudiness will go away on its own in 24 hr.

watch your humidity in your spray area and keep well ventilated till dry

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Thanks, John. 50% humidity would be a swamp for this area. 25% is our normal high humidity.
Never tried any shellac flakes, unless there's something wrong with using the Cardinal Vinyl sealer, I'm gpnna try it first. I do appreciate the inputs, and will follow your thinning advice. Roy

Roy, I remember one exchange we had where you were getting white stains around joints mostly in the butt graft area of the guitar. I said it looked like residual glue staining and suggested more prep sanding to get rid of glue residue on the exposed surfaces. I seem to recall you did this and then got better results.

finish is more about prep and details.
there are no short cuts

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Barry, You remember correctly. I've been playing my third guitar for well over a year or so happily, but have recently noticed some of the same symptom starting around a couple of glue joints, but so far they just show up as a feel rather than visibly. I'm hoping that combining the blacklight glue inspection with more consistent coverage of vinyl sealer will stop this problem...seriously doubt that changing the pore fill has any effect, but I was willing to try anything that might fix this issue. It's always frustrating to get an issue that doesn't show up for what seems like a long time. Appreciate inputs, thanks for helping me chase down another of my deficiencies. Roy

If you can rule out that surface prep is an issue, then it must be something with your finishing process. I would suggest simplifying so it's easier to rule out other things. Like the vinyl sealer is definitely not necessary so skip it next time. Just do a thin coat or two of lacquer which I often use for sealer.

Roy, could it be possible that you are sitting the guitar on any surface during the finish process, including during sanding between coats. I am suggesting that surface contamination might be a contributor to the problem.

Wow, I'm uneasy about eliminating the vinyl seal, or if not that, then a spray of shellac, which I've never done before since I've never dealt with flakes. I could eliminate the retarder, but since it's only at glue joints where I see the problem, I doubt that is the problem or surface contamination which should show up in other places. I would be more inclined to think I don't really understand how to tell if I've completed the prep perfectly around glue joints so I decided I'd ask for help before plunging ahead with spraying. Is there a better way to tell the glue joints are ok other than a blacklight? And if I see places I think could be a problem, can't I just make sure I have them covered with brushed on Zinzer shellac before spraying the vinyl sealer?

For the sake of clarity, do you mind sharing which vinyl sealer and which lacquer you're planning to use? Sorry if I missed it above.

FWIW, I've always used Z-Poxy and have never had problems. I love the way it pops figure.

I've specifically sprayed a few guitars using Cardinal vinyl sealer and lacquer. Not all vinyl sealers are the same. For example, McFadden's needed to be scuffed unless fresh. Mohawk and Cardinal need to be scuffed, period.

I don't recall whether or not I thinned Cardinal sealer, but can tell you I had adhesion issues when I didn't scuff and had to re-do the finish.

Do you have a pic of the issue on #3?


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Blush is gonna happen. Just be prepared for it. I keep a small gun on low pressure to spray small amounts of blush retarder when I see it. Key is, small amounts. Also put in lacquer to help minimize. But if humidity is up, you still gonna need the backup gun. Vinyl sealer: only use on spruce tops. I never spray it. I rub it on with a clean cloth. Reduces need for post sanding cleanup. My 2cents (in my book pore filling a sealing are two diff things). Pore filled wood does not need a sealer)

Cardinal Lacquer, thinner and vinyl sealer..There are no pix to show for #3, it's just that the edges of the end wedge which were perfect to the touch originally are now starting to raise enough that I'm expecting visible problems in the future since I can readily feel that interface line. I'm not even sure blush is the right term for what I've been experiencing. I could certainly show a pix of #2 around the rosette, I know I've shown that in previous posts. I've never had a problem with the purfling where I use CA for adhesion. I do spray 3 coats in a day typically, then use 360 grit lightly before the next day's spray. When I'm done, the guitar hangs for 3 a month before I start wet sanding/levelling.
Mike, you rub on the sealer, is that straight or diluted? If that's the case, why couldn't I just rub same over all the glue joints I suspect might cause a future problem? And, come to think of it, why do you use sealer on the top? Some previous problem that was fixed that way? Thanks, folks. I'm not panicking, I'd just like to make sure I've corrected problems with each successive build, and I'm not totally sure I have on #3, although it is the best I've done so far. Roy

I just trying to think of ways to rule out the issue, and vinyl sealer is not really necessary. For years I shot just straight lacquer and never really had a problem due to a lack of a sealer coat.

This doesn’t sound like blush - a milky or whitish haze of moisture trapped in lacquer - but like the sinking of lacquer over a glue line, a totally separate issue that no amount of retarder will help with.


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It can be left orver glue as stated above or even some of the epoxy. Learning to prep properly takes time. I find wiping down with Naphtha will help show points of excess filler and glue.
Can you post pics?
tite bond has been being used for years. I have seen sinks in finish at joint lines. Vinyl sealer is softer than nitro. I stopped using that and use shellac flakes and ever clear.
Humidity causes funny things from swelling and expanding

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

The LMI glue can be seen with a black light but I don't think Titebond has that property. Sufficient observation should be good enough though imho. Perhaps with the aid of magnifying glasses. Naptha sounds like a good idea. I use a damp rag since I want to raise the grain anyway and that often times shows some flaws.

You can def rule out blush if you spray (lightly) some retarder on and it does not go away. One problem with this is if you sprayed several layers over the "blush". Releasing moisture is best done as soon as you see it (after coat flashes). I pore fill with epoxy. I see no need for a sealer on hardwood (that has been epoxy pore filled). In fact, my last coat over epoxy is a super thin washcoat of epoxy (roughly 50/50 epoxy/DNA). But you gotta let this cure a good day before you spray lacquer. AS for the top? I like rubbing the straight-out-of the can vinyl sealer. I can't give you a solid reason why. I like the bit of hue it provides. So, I guess it is because I like it.

I gave up spraying vinyl sealer. Looks like peach fuzz. Too much rework to get it right. You really should post pics. ask how if you don't know how. You got some big dogs in here paying attention (me excepted). THey can help better with some visuals.

I don't have any visible issue on #3 so far, just an area where the end wedge interface line has developed a 'feel' which was originally perfectly smooth that had me a bit worried. Here's a pic of the typical problem I had on #2..always at a glue line. Not the light reflection, just the purfling interface.


Calling it blush was clearly a mistake, it's more that I'm not clear how to make sure I don't have residual glue still there even though I can't readily see it before I start spraying. I'll try some naptha as John suggested.

It does make sense that the back and sides should not need a sealer, unsure about the top at least at the rosette and whether it would be good insurance at the end wedge. I suspect the original process with Zpoxy is probably ok once I learn how to make sure the prep during sanding is perfect. Thanks for the inputs. Roy

Looks like delam to my untrained eye.

What is the white, is it plastic?


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It looks like it starts on the plastic. The finish also looks very thick which could be a part of the adhesion issue.

What kind of glue do you use with the plastic purfling?

That was my first thought, too.

Is this Cardinal vinyl? Was it scuffed before the first coat of lacquer?


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that is a delam it isn't blush.
so did you sand with grit finer than 220 on the body? I found 150 is sufficient. You need to let some tooth for the finish to hold on to.

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

oops, thought i answered this last night...yes, the worst spot in that pic does flex, so it is a delam. It wasn't until my third guitar that I realized I should sand in between each day's coating of lacquer, and I have been using titebond on the end wedge, partly because those wedges were so large. Yes, it's Cardinal brand. I believe I had sanded with 320 before I started any spray. I'll stop that at 220. Also, I started out thinking I needed quite a few coats to keep from sanding thru on the edges. I think I had done like 12 coats. So by the fourth, I was sanding with 360 or 320, don't remember after each days coating, usually 3 sprays in a day. The next morning I would sand lightly, then spray again, with a little extra spray on the edges. (Sounds like I should let each day's spray rest a day before I start scuffing?) I kept spray records, but only on scratch paper, so not sure how many coats I did on #3, but I'm pretty sure it was still 9 or so. I've never scuffed with anything coarser than 320, sounds like I can go to 220 anyhow. On my first tries I could still see sandpaper tracks thru the lacquer, so I wasn't sure if they were all from wet sanding or mebbe earlier. 150 sounds a bit too rough for my level of competence. At any rate, I think I can get started spraying with the inputs y'all have provided. I'm still thinking I'll do some shellac or sealer by hand on the end wedge edges; possibly the rosette too although I don't remember needing to do any glue there, just CA.
Be back with pix in a few months, working with my normal alacrity and 2-3 hour work day. Thanks for the help. Roy

I had adhesion issues the first time I used Cardinal vinyl and lacquer. When I contacted them, their specific recommendation was to scuff the vinyl sealer with maroon Scotch-Brite before spraying lacquer if the sealer had been on the guitar for more than 45 minutes.

I’m confident this is your issue.


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