Official Luthiers Forum!

I meant,what is the base? nitro or polyester?

Brad, read the entire thread start to finish. By now all the information is in there other than all the part numbers.

The rosewood sealer is a two part urethane. It's neither nitro nor polyester.   It's used as an isolator to keep the rosewood (and other wood) oils isolated from the polyester as these oils prevent curing of the polyester. Think of it as a barrier coat where the epoxy or Waterlox are being used as tie coats.

Thanks,Rick

Very interesting reading for sure! I looked into polyesters over here (ie, Europe), and found it difficult to find details on the use of the products I found for wood finishing (no 'rosewood sealer', that's for certain), and the manufacturers weren't all too interested in selling to private individuals. So...yeah. Gave up on that one.

Thanks again to Rick for detailing his bridge gluing method using CA.

What do the rest of you polyester users do? Does the toughness of this finish require a different approach to removing the finish for gluing on the bridge, or does the usual method of scraping work just fine? Do you rout it off? Do you remove finish all the way out the outline of the bridge, or do you overlap a narrow border of finish around the edge - and, if the latter, do you rout a tiny ledge around the underside of the bridge? Is there anything about the behavior/properties of this finish that has caused you to do this step in a different way than you had before? Or is it just a matter of personal preference, no different from how one might do it with any other finish?

Thanks.

_________________
Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

I use my router. No ledge; my bridges are small enough as they are; no need to make the gluing surface smaller....

Matt Mustapick had just picked one up from Addam Stark when I visited.
Addam had used some sort of film, and Matt just needed to trace it with
an exacto and peel it up. I want to say frisket film, but Matt only
mentioned the name for a moment, and that's what I remember.
Hopefully it's close.

Todd,
   I use the traditional approach for remoing the finish before bridge
installation. I am careful when preparing the bridge area prior to finsh
though. I mask to within 1/32" of the edge of he bridge all the way
around and then make an intial razor cut around the edge of the masking
and peel it away leaving just that 1/32" of finsih around the perimeter.

   I then cut right to the edges of the bridge and use a small dogleg chisel
to remove the remaining line to the new razor cut. A fresh, brand new
blade in the Xacto knife for each bridge gives me great control over
direction and depth to avoid getting into the grain of the top when
cutting.

    I've considered using a narrow ledge around the bottom edged of the
bridge to allow it to set down into a smaller opening in the finsh, but just
don't trust the smaller glue footprint.

   It's just the way I've grown comfortable doing it, but I'm sure there are
quicker ways. I enjoy this method and don't plan on changing any time
soon.

Regards,
Kevin Gallagher/Omega Guitars

[QUOTE=grumpy] I use my router. No ledge; my bridges are small enough as they are; no need to make the gluing surface smaller....
[/QUOTE]

So, you remove the finish right to the very edge of the bridge outline. Do you actually rout right to that line, or do you rout very close and then scrape right to the line? In the corners, at least, you must do a little scraping, right? No issues with scraping polyester?

_________________
Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

[QUOTE=James Orr] Matt Mustapick had just picked one up from Addam Stark when I visited.
Addam had used some sort of film, and Matt just needed to trace it with
an exacto and peel it up. I want to say frisket film, but Matt only
mentioned the name for a moment, and that's what I remember.
Hopefully it's close.[/QUOTE]

Very interesting. I'll have to talk with Addam about that. Thanks, James.

_________________
Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

[QUOTE=Kevin Gallagher] Todd,
   I use the traditional approach for remoing the finish before bridge
installation. I am careful when preparing the bridge area prior to finsh
though. I mask to within 1/32" of the edge of he bridge all the way
around and then make an intial razor cut around the edge of the masking
and peel it away leaving just that 1/32" of finsih around the perimeter.

   I then cut right to the edges of the bridge and use a small dogleg chisel
to remove the remaining line to the new razor cut. A fresh, brand new
blade in the Xacto knife for each bridge gives me great control over
direction and depth to avoid getting into the grain of the top when
cutting.

Regards,
Kevin Gallagher/Omega Guitars [/QUOTE]

Thanks for detailing your method, Kevin. That's very helpful.

So, I take it you don't mind doing the leveling on the finish with that masking tape on there? Do you just level right over top of the masking tape, or do you have to sand carefully right up to the edge of the tape? Or do you not do any leveling until the tape is off? (Please be patient with me, understanding that my experience with finishing guitar tops to date is limited to french polishing.)

Thanks again.

_________________
Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

Todd,
    I level the entire finish with the masking material in place. Being .004"
- .005" thick makes the masking a very convenient reference for my final
sanding to a known thickness.

   As I sand the areas where the fingerboard tongue and bridge are going
to be glued, I'm careful to not break through and lift the masking during
sealing and initial coats, but sand right to it and even break through when
sanding and leveling final coats.

   I should have clarified this during my first post...sorry.

I hope it helps a little,
Kevin Gallagher/Omega Guitars

level the entire finish with the masking material in place. Being .004"

- .005" thick makes the masking a very convenient reference for my final

sanding to a known thickness

I hadn't 'seen' that benefit. Must to try....

Todd, yes, pretty well right up to the edge. I score a line around the bridge with a new blade, rub some blue chalk into it, and rout right to that. I may leave just a bit, and will chisel that off, as well as finish off the corners. Takes -some- confidence in your routing abilities to convince yourself to do it, but you're only routing off a few thousanths, and there's little chance of the router grabbing and doing anything bizzare. I use a PC 310, BTW. Two layers of masking tape(one strip, two thick) on each side of the bridge or fretboard for the router to ride on.

Method(s) subject to change at any time....

Mario nailed it with "Method(s) subject to change at any time..." I am always willing to experiment to find a way to cut out a day of spray, cut back from six coats to three or four, fill pores a different way, learn new color methods, get better adhesion, etc.   I think I'm at a point of diminishing returns, but I have gotten finish down to three or four days worth of in-booth process, 24 to 48 hours of cure before rubout, and good enough adhesion to glue bridges directly to finish. That's pretty good for doing about 30 instruments a month.   

Rubbing some "blue chalk into the scribed line." Good grief that is so simple. I would never have thought of that. And I'm zeroing in on this very process sometime in the next couple of week. Great tip. Thank you Grumpio!!!!!!!

Quick question for anyone who knows: can you rout nitro off of a guitar the way you apparently can polyester, or will nitro flake off, or melt?

Thanks again.

_________________
Eagles may soar, but weasels don't get sucked into jet engines.

Nitro routs off similarly...I've done it on 3 guitars.

_________________
JJ
Napa, CA
http://www.DonohueGuitars.com

I've been away for a few weeks, and here I find a great thread when I come back...marvelous!



Any of you finish pros have any comment or experience on water white
conversion varnish?  Its apparently pretty popular with the
cabinet guys round these parts (MD).  I'm using a pre-cat
available locally, nice and clear, ready for sanding in an hour, ready
for buffing after ~3 days.  But the MSDS is notoriously vague on
the chemical makeup.  How does it compare with polyester or
polyurethane?



I've also heard of "catalyzed lacquer" and wondered if this is the same
stuff (but the coats don't melt together like nitro).  FWIW the
guys I buy from recommend I cut it (and clean up) with standard lacquer
thinner, and so far it seems to work without a problem.

Well, I spent a fair amount of time in redaing this whole thread and am very glad I did.
Thanks to everyone, wish I could contribute but I only know nitro.
I'm going to have to give this some serious thought.
Thanks all and welcome back grumpy!

_________________
Jim Watts
http://jameswattsguitars.com

Every month someone wants to try some furniture finish. I say go ahead and do it; it's your disaster in the making, and I'm staying well away from it. Companies like Lawrence McFadden have formulated finishes specifically for guitar making, and they work just great. Why on earth go experimenting with something else unless there is a really clear reason to do so? It's hard enough getting what we know works down pat.

I say go ahead at your own peril. I know what works, and I've got pals who know other materials that work. I'm not interested in any more Crystalac type disasters, Sherwin Williams Polane disasters, etc., etc.   I'm interested in refining the wheel but not reinventing it.   

Rick, Grumpy (or Sneezy, Happy, Dopey, Doc, Bashful, et.al.) <BG>...or other historians:

...What were the gory details of the finish disasters? While I'm not interested in trying such materials, it's nice to have one of the resident historians quote the past accurately so that we don't repeat such follies. TIA

_________________
JJ
Napa, CA
http://www.DonohueGuitars.com

Thanks, Kevin and Mario, for responding with the details I was asking for. Much appreciated.

Now, Rick, Mario, Kevin, and other polyester users, if you can stand me asking yet another question...

The subject of what "wets" the wood nicely has come up in passing in this thread, but hasn't really been addressed directly. Mario says he uses a Chemcraft sealer, and that this " 'wets' the wood as well as anything I've seen". Rick has been talking about his use of epoxy pore filler, rosewood sealer, and Waterlox tie coats, but hasn't mentioned the wood wetting effect specifically.

Many have commented in the past how they love the wetting effect of epoxy, and how they will apply a coat of epoxy thinned with alcohol after completing the pore filling process, even if they've sanded the whole surface back to the wood up to that point, just to utilize the epoxy for it's very nice wetting effect.

So, my question to all of you: in your polyester finishing schedule, are you pleased as punch with the look you're getting with regard to the wetting of the wood (enhancement of the natural color, depth, and "glow-from-within" of the wood)? If so, what material (epoxy or your sealer or what) is doing the job for you?

Do you use a sealer on the soundboard, or is polyester sprayed directly onto the spruce or cedar or whatever (I'm assuming a natural finish here, no sunburst or anything)? In this or any situation where the polyester may be sprayed onto bare wood, how well does it "wet"?   

_________________
Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

My major finish disaster was with Crystalac. I'd get it all rubbed out as well as it could be done, and if I laid the instrument on a workbench overnight, it would be ruined the next day from imprinting. Or if it went into a case. Or if it went onto a guitar stand. Then there was the issues I had before I decided to just blow rosewood sealer on everything. The oils in cedar can prevent polyester from curing, and we had some instruments where the surface was cured and the poly next to the wood was a gel. The only other major problem was not getting the polyester/catalyst ratio right and having it go off in the gun.   

McFadden's rosewood sealer seems to wet the wood identically to epoxy, so I don't do the thinned coat of epoxy step, I go right to the sealer.

[QUOTE=Rick Turner]   

McFadden's rosewood sealer seems to wet the wood identically to epoxy, so I don't do the thinned coat of epoxy step, I go right to the sealer.[/QUOTE]

Thanks, Rick.

Do you put the sealer on spruce as well?

_________________
Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/