Official Luthiers Forum!

Last week I discovered what looked like a large sweeping scratch on my OM back, and I thought I must have scratched it badly without knowing it. Tonight I took it out to play, and found more of the "scratches" on the back, one on the top, and many on the neck and headstock. I am going to have to refinish the whole instrument, again.

I don't have any clues as to why this is happening, but as I said, The finish looks like a cross between crazing and scratching. It is as if the finish kept shrinking and shrinking until it could no longer hold together, and just split apart randomly all over the place.

Also, there were a few places where it shrank up to the point where some dust particles were popping through the finish, and in those places, the finish actually started to delaminate around those particles.

I'm hoping Vijay will stop in and share anything new that he has found in his efforts to find out what went wrong with Tim McKnight's guitars.

I'm pretty sure that climate hasn't been an issue since it has remained in an air-conditioned room for the last many weeks, which is pretty well in the 50 RH range, or a bit higher. Never drier really. Stored in an Ameritage case all latched up.

Fortunately for those who are not spraying this, this seems to be a non-issue, but there is a definite problem with spraying it.
I'm going to have to dump the remaining cans of this particular mix, and get some fresh stuff from Vijay at the thinner mix and see how it goes.

I'll post some pictures when I have better light to take some.

_________________
"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."

Do you have pictures?

I have never used Royal-Lac and this is all complete conjecture as I have no experience or connection with the company or product, but I have heard it's basically shellac with some additives to make it super hard/durable? I know shellac cures mostly by evaporation and shrinks quite a bit as it does so, and that synthetic polymer guitar finishes generally cure relatively fast and very hard and don't shrink as much. I wonder if trying to get the best of both shellac and poly worlds may have the unintended real-world consequences of trapping a shrinking gel in a rigid, brittle matrix... creating tensions via much different shrinkage rates that may never reach equilibrium until things go bad. Seems a bit to me like gluing stiff dry bracing to a green back plate, and we all know how that ends up...

Again, I am just thinking out loud and I have no experience with the product or folks who supply it... I wholeheartedly hope to hear my thoughts are baseless and this finish proves to be as good as advertised as it would be something I would love to trust on my own instruments.

To the extent there are problems, aren't they limited to spraying? I have not heard of anyone having trouble with hand application of Royal Lac. I know it worked great when I French polished with it.

I wonder what the methods of application have to do with the price of tea in China?

I really want this stuff to be the Next Great Big Thing, so I can use it.

Nobody that I am aware of has had any issues with padding it or french polishing it.

James, I had the same basic thought.

Ed, the reality is that it seems to be a factor, or perhaps the real issue is film thickness...

_________________
"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."

Don't know anything about Royal Lac except it is shellac based, right?
I have plenty of experience with violin spirit varnish (also shellac base) and it can check if too many coats are applied without much drying time between coats. Heavy coats are also prone to check as they take longer to dry...

UPDATE

I have heard back from Vijay, and the issue was because of the mixture of the 26% solids formulation was calculated incorrectly, and this is what caused the failure of the finish.
I will be re-spraying the guitar with the correct (normal solids) product and will hopefully have much better results to share. Nobody has had any issues with spraying the normal solids mixture from what I have heard.

Haans: Thanks for the info. I don't know if that played a role as well, but I guess it is possible.

_________________
"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."

Very keen to understand this, Don; can you expand on how/where this error was made?




Sent from my iPad using Tapatalk

Whew, I just finished spraying a mandolin with RL and am waiting for it to finish curing for final level/polish. I used the standard formulation so sounds like I should be ok.

_________________
Steve Smith
"Music is what feelings sound like"

Sorry to hear that this is happening Don. Not much to add except one thing...

My steel trap memory (cough, cough...) recalls back in the day when a "hard shellac" product emerged from OZ and was marketed to Luthiers. Many of us bought in and loved the idea of a shellac finish only one that was billed as harder, more ding resistant, etc.

Folks used it and being the coward that I am... I held off to wait to see what happened with the instruments others finished. In short order they were reporting very much the same thing. See the ANZLF back in the day for details. Cracking, crazing, etc.

It seems the finish lacked the needed plasticizers to permit it to expand and contract in time as our guitars always will be doing too.

I have no idea if what you have is the same stuff reborn because that's what they did with the OZ finish, went back to the drawing board and rereleased it. But it was shellac and it had additives to make it tougher and hopefully more flexible.

What you are describing though sure sounds exactly to me like what happened with the early iterations of the hard shellac from OZ.

Oh yeah, I got rid of my two bottles....

I guess I should have explained myself better, so here goes:

There is a normal version of Royal Lac. However, some folks want to spray Royal Lac, and they feel a different solids ratio will help them do that. So those folks have asked the maker of Royal Lac to give them a special formulation of the product, and he has done that for them. It turns out that an error was made in the special, spraying formula batch sold to Don, and that has caused, or contributed to, Don's problem here. I don't spray, I hand apply, so I wanted to make sure nobody has heard of any problems with the normal formula that I have used.

I hope that helps my question seem more relevant.

That is precisely it. The mistake was made in the calculation of the ratio of shellac to other components, which caused the finish to not cure properly and created the bad shrinking and subsequent cracking issue.

I will be using the original formulation to refinish it. I had no trouble spraying the thinned out version of the 26% mix, which is pretty much the same consistency as the normal product, so I will spray again. I'm not concerned about speed of building up layers, so it works for me.

_________________
"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."

So, to be clear, this was an error in formulation from the supplier. Not trying to bash Vijay here; he's obviously a very responsive bloke. I accept the need to "beta-test" this stuff., and the chances of error in producing special mixes is high.
I'm really hoping this will prove to be a good alternative to nitro or poly. I've got lots of experience with pre-cat poly and have been getting good results, but my stock was from New Zealand, and I can't get it here in Canada. Furthermore, I can't imagine exhausting all the warm air from my house in the middle of Quebec winter, which is what my explosion-proof fan will want to do, so something less toxic is required if I hope to spray more than 4 months a year! I'm following the Royal-Lac experience on this forum with great interest.


Sent from my iPad using Tapatalk

To what Hesh said, shellac is, as he says hard. In violin spirit varnish, the natural plasticizers are added, but there is still a BIG problem if the finish is "piled on". There is no problem with French polishing as there is an oil agent used in application and there is a dry time that is pretty much covered with the oil. However, with a sprayed shellac varnish, alcohol evaporates so rapidly, the outside layer skins over very quickly. That is why on humid days it blushes at the drop of a hat. It is nearly dry when it hits the wood. Heavy coats, several per day build up and the outer layer of the first coat melds with the 2nd layer's inner coat which has a skin of its own. That becomes the new outer layer, but the first coat's inner layer is still soft.
So, now you have a soft part with outer skin (1st coat) bonded to the 2nd soft part with a dry outer skin (2nd coat). Shoot 4-5 coats and you have alternate soft, hard, soft, hard, etc. The very first coat finally dries through evaporation of the solvent through the wood, but the rest is trapped and takes quite a while to slowly dissipate. While this is all going on, the very outside of the finish is getting very hard and finally something gives and the outside finish checks.
I hope I have explained this in a way that is understandable, but it is basically that the outside has shrunk to a size, and when the finish under it finally dries, it checks.
I liken it to painting egg whites over fresh dry varnish where the egg whites will stick like crazy to the finish, and when they shrink and dry, they craze the finish of the varnish.
As a side note, many of us that used to spray spirit varnish remember Behlen's violin varnish. It would skin over not so quickly, but if you sprayed more than a coat every other day or so, you would end up with a finish that would almost never completely dry. One wise spray finisher said once that many thin coats are better than few thick coats. It's usually because thick coats check and thin coats will dry quicker before adding another. I hope this sheds a little light on spraying with spirit varnish. Patience is the order of the day.
AND, after all that, I might say that I prefer checking and crazing on my mandolins, so I go out of my way to use spirit varnish over oil varnish. the spirit dries quickly and the oil varnish very slowly underneath so that eventually the spirit crazes.
Just call me funny that way...

I tried to warn y'all a few months ago. The crazing won't show up for a month or three. Its disheartening to say the least. BTW, There are no paint strippers that will phase this stuff after its cured for a few months. You will have to sand it off

_________________
tim...
http://www.mcknightguitars.com

Ah Tim, but I was already deep in the process when you warned us!

Have you found that you can spray the normal formulation without issue??
That is of course my one concern now. Otherwise, I'm going to pad it on.

_________________
"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."

Tim, I was unaware of your issue. On a whim, I Googled it. Did you know (from at least my simple search: McKnight Guitars Royal-Lac) that what shows up makes you seem a proponent of Royal-Lac? I think someone is controlling what gets posted at the top of a search. Maybe I am confusing the spray versus rub issue.

Tim was / is a proponent of Royal Lac. It was the 26% solids mix that was the issue, and the ratio of shellac to additives.
Hopefully Tim will clarify. At one point, RL was his go-to finish.

_________________
"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."

Ive brushed, padded, and French polished Royal-Lac with no problems so far. Don when you spray the normal formulation do you cut it back? If so do you use the denat. alcohol Vijay sells? I am thinking of spraying my next two guitars. Glad to see this discussion.

Gil, I have not used the normal formulation, so cannot say. I am hoping someone will chime in who has.
While I did dilute the 26% down, it simply added more solvent and the improper ratio of shellac to plasticizers etc remained.
I probably will thin it a bit, and keep the costs as thin as possible.
Still hoping to find success spraying it.

_________________
"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."

Gil, I've been spraying Royal Lac and so far I am liking it a lot. This is my first experience but here's what I've done which is basically copied from Robbie Obriens finish schedule.
1. I sanded to P320 then sealed with Seal Lac straight out of the can (I believe it's a 2# cut). I used standard blend Royal lac also straight out of the can for 12 coats of build, I did 4 coats about 30 min apart, skipped a day, scuff sand with P400 then repeated.
3. Did an initial level sand with P600 then sprayed 4 finish coats. I thinned the Royal Lac 20% with Everclear and I tried to spray the finish coats wet.

Robbies's initial tests can be found here: http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=45798

_________________
Steve Smith
"Music is what feelings sound like"

I actually asked Vijay about Seal-Lac recently for another reason. It's about a 2.4 lb. cut. Royal-Lac (the regular formation) is a 2 lb. cut.

Thanks James. It sprayed good though.

_________________
Steve Smith
"Music is what feelings sound like"

Thanks guys. Steve I would like to see your guitar you sprayed sometime. We should meet up soon!