Official Luthiers Forum!

I got Robert O'Brien "Guitar finishing" DVD yesterday, great DVD by the way,
very concise, educating and the FP part definitely enlightened me. For pore
filling he shows a technique using wood dust and shellac. That looks very
appealing, definitely less messy than the oil or water-based pore-filling
products I've used before, but I'm wondering if the shellac and dust mix will
not sink into the pores after a while. Anybody tried this method? Robert,
how are the guitars where you used that technique? I finished my first build
entirely with shellac and after 4 months I can see the shellac has shrunk
slightly and some pores are appearing in the IER, very slight, but noticeable.
The grain lines are definitely showing on the top as well.

_________________
Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

Thanks for the compliments on my DVD. I hope you find it informative. The shellac and sawdust method is one of my favorites precisely because it is quick and easy with little mess. I usually use it under a high solids finish such as a cat urethane. However, it will shrink back a bit over time like most fillers and finishes do. If you want to almost guarentee a glass like finish forever I recommend you use an epoxy or a polyester selaer for example. My opinion and personal tastes are that I don't mind a finish showing a few pores after shrinking back as long as it is uniform and not just in one area. It shows that you were able to kit a thin application of the topcoat product and buff it out without going thorugh it. This is a real trick with a urethane for example that builds in layers as oppossed to lacquer that melts into previous layers creating one thick layer. It also allows the wood to show through a finish instead of just having a "plasticized" guitar. IMHO your guitar will sound better too.    

Thanks Robbie, that answers my question. So in other words, this wood-
dust/shellac method does not shrink more or less than a traditional pore-
filler. One kind of finish that isn't covered in your excellent DVD is
traditional oil varnish (non poly). Like Behlen Rockhard. I'd be curious about
the application methods, drying time, finish condition and so on.

_________________
Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

That is correct. It shrinks about what you would expect other pore fillers to.
The application method for all oil varnishes is basically the same. I mention this in the DVD and just happen to use one with a poly resin for demonstration purposes. You can use the info provided to have a working knowledge of oil varnish finishes and then adapt that for use with another brand name if you like.

I'd like to try Behlen Rockhard varnish, would you recommend the dust/
shellac pore filling technique before applying the varnish? Will the
cheesecloth method work with it, or is it better to use a foam or bristle
brush?

_________________
Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

Robbie,

I got your DVD as well and have gotten a lot out of it. Thanks!

Before getting the DVD, I'd started working on the finish on an EIR guitar with white/black fiber purfling (rosewood binding). My plan has been to apply a very thin film of shellac, then top coat with McFadden's wipe-on gel polyurethane. Although my goal is a thin satin finish, I don't want the look of the deep, craggy pores of this rosewood being left open. I thought I'd fill the pores just by applying several coats of shellac and sanding back, partly because I would ideally like the filler to be transparent. I don't know how many coats of shellac I've brushed on and sanded back now - lots! - and the deep pores in this rosewood are still not filled. The shellac in the pores is shiny, and this shows through the satin urethane on my test piece and looks like crap (aside from the pores, the finish on the test piece looks great!). Time to try another method of pore filling. I'm thinking of trying the wood dust/shellac method you describe, but I have a couple concerns and ideas I hope you might have thoughts on.

First, the white fiber purfling will get messed up unless I seal it off. You recommend lacquer for this. I don't have any, and hope to avoid using it in my shop at all if I can. So, I wondered if you'd ever tried anything else for this purpose. On hand, I have the McFadden's urethane gel and some Zar regular liquid polyurethane, not to mention an assortment of glues. Any thoughts?

Second, the wood dust will create an opaque filler, and I'd prefer it to be clear. So, I had this idea: what if I use silica powder intended for thickening epoxy instead of wood dust? Ever try it? I suppose the silica might abrade the wood and create dust, thereby defeating the purpose. Any thoughts?

I think it would be a fair amount of work to remove all the shellac that's already in the pores, if that even could be completely accomplished, otherwise I'd consider starting over and using epoxy to fill instead. I don't know, maybe a thorough soaking of the surface with alcohol would remove all the shellac without too much difficulty.

Thanks in advance for any helpful advice you can give me.

I hope this is on-topic enough to not constitute a thread hijack!

_________________
Todd Rose
Ithaca, NY

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

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

[QUOTE=Todd Rose] Robbie,

I got your DVD as well and have gotten a lot out of it. Thanks!

Before getting the DVD, I'd started working on the finish on an EIR guitar with white/black fiber purfling (rosewood binding). My plan has been to apply a very thin film of shellac, then top coat with McFadden's wipe-on gel polyurethane. Although my goal is a thin satin finish, I don't want the look of the deep, craggy pores of this rosewood being left open. I thought I'd fill the pores just by applying several coats of shellac and sanding back, partly because I would ideally like the filler to be transparent. I don't know how many coats of shellac I've brushed on and sanded back now - lots! - and the deep pores in this rosewood are still not filled. The shellac in the pores is shiny, and this shows through the satin urethane on my test piece and looks like crap (aside from the pores, the finish on the test piece looks great!). Time to try another method of pore filling. I'm thinking of trying the wood dust/shellac method you describe, but I have a couple concerns and ideas I hope you might have thoughts on.

First, the white fiber purfling will get messed up unless I seal it off. You recommend lacquer for this. I don't have any, and hope to avoid using it in my shop at all if I can. So, I wondered if you'd ever tried anything else for this purpose. On hand, I have the McFadden's urethane gel and some Zar regular liquid polyurethane, not to mention an assortment of glues. Any thoughts?


Second, the wood dust will create an opaque filler, and I'd prefer it to be clear. So, I had this idea: what if I use silica powder intended for thickening epoxy instead of wood dust? Ever try it? I suppose the silica might abrade the wood and create dust, thereby defeating the purpose. Any thoughts?


I think it would be a fair amount of work to remove all the shellac that's already in the pores, if that even could be completely accomplished, otherwise I'd consider starting over and using epoxy to fill instead. I don't know, maybe a thorough soaking of the surface with alcohol would remove all the shellac without too much difficulty.

Thanks in advance for any helpful advice you can give me.

I hope this is on-topic enough to not constitute a thread hijack!


[/QUOTE]
FIRST: Any poly or lacquer will work. Make sure the solvent is not alcohol. I have used sanding sealer before with great results. Just thin whatever product you are using by about 50% Use a q tip to apply it to the white purflings and other areas you don't want to get stained form the shellac and sawdust. When you sand the excess pore filling residue off the sealer used for the purflings also sands right off.


SECOND: Opaque pore filler is not necessarily a bad thing. YOu can use a darker pore filler to accentuate the pores in wood with a nice affect. I feel it gives the wood more warmth and character. Mahogany looks great with a darker pore filler. Just make sure you get it all off the wood before topcoating.If you are going to use silica in the mix why not just use epoxy to begin with? Also, if you are going for a satin look why are you so concerned about using a transparent pore filler?


The reason why you are having trouble filling your pores with just shellac is that shellac is not meant to build in the way you are using it. Each new application melts the previous one and you probably are just pulling it out of the pores again. The solid content is relatively low in shellac. I use the sawdust for the solids and the shellac as a binder to keep it in the pores. I would lightly sand the surface you have now and then go right over the top with your pore filler of choice. Just leave the shellac that is there alone. Let it sit for a bit before you pore fill so that it shrinks back and then move forward.

I might mention here also that too thick shellac will often bridge pores. you may think they are filled only to have the shellac sink into bridged pores.

Does anyone use pumice for pore filling? I used that on the back of my first guitar(I left the sides unfilled to see what it would look like) and really like the results on the back, but it was a lot of work.

I'm not so happy about how the sides turned out.

[QUOTE=Robbie O'Brien] YOu can use a darker pore filler to accentuate the pores in wood with a nice affect.[/QUOTE]

Yeah, it works really well (in my limited experience). I was having a really difficult time finding a good color to mix with some neutral LMI acrylic pore filler to use on an oak (chambered) solidbody I was building.   Every combination I came up with looked just awful on test pieces. In frustration, I made some mahogany dust and used it with pumice/shellac, and it really popped the excellent grain of the oak, making the fill look really natural! I bet there's an appropriate wood dust match for filling just about any tonewood--and no artifical colors!

Thanks, Robbie, for addressing my questions. Thanks also to Michael, Graham, and Carlton for your input.

Robbie, in reply to your questions...

"If you are going to use silica in the mix why not just use epoxy to begin with?"

In hindsight, I think that would have been a good idea. But now that I've got shellac in the pores, I'd have to remove the shellac first in order to use epoxy, since (as I've been informed) epoxy won't adhere to shellac. I'm uncertain about whether I'd be able to get all the shellac out of the pores, and whether I'd just make a mess trying. That's why I'm considering using silica with shellac now - again, the idea being to possibly create a more transparent fill.

"Also, if you are going for a satin look why are you so concerned about using a transparent pore filler?"

On my test pieces, with a light build of shellac (wiped on) followed by 5 wiped on/wiped off coats of the McFadden's clear gel urethane, I'm getting a very nice look (except for the pores) that is satiny in sheen, but at the same time has great clarity and brings out the natural depth, color, and 3-D shimmer of the wood. My thought is that a transparent filler would enhance that depth, that 3-D effect of peering into the wood.

My plan to fill the pores with brushed on/sanded back shellac came from the description of that technique from a couple of different sources, e.g. Bob Flexner. I suspect it would work fine on smaller-pored woods, but this rosewood... if you don't watch out, you could fall into one of these pores and never be seen again. The shellac has gotten closer and closer to the top of the pores as I've worked; some pores are filled. But it's just taking a ridiculously long time, and I've thrown in the towel on that attempt.

Since I'm doing a satin finish, I don't even care if the filler were to shrink back significantly after I'm done. It's just that, with the shellac in the pores still below the surface, I can't sand the glossy sheen off of it, so it shows up as all these shiny flecks, even through the 5 coats of satin urethane (I haven't put the urethane on the guitar yet, that's just what I discovered on a test piece). That looks really bad.

I don't know if you have any more thoughts on the possibility of using silica with shellac, or any other aspect of this, but maybe you at least have a better idea of what I'm working with and trying to achieve. I really appreciate you taking the time to help.   

_________________
Todd Rose
Ithaca, NY

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

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

Robbie's input never ceases to amaze and intrigue. I'm very thankful to learn from such an insightful instructor.
Robbie, you must have been jones'n for the OLF, you've been posting like mad since you got back.
-j.

_________________
“If God dwells inside us like some people say, I sure hope He likes enchiladas, because that's what He's getting”
-jack handy

Robbie, in your DVD, before showing the FP technique, you fill the grain with
a dark grain-filler (I assume water based), but you might as well have filled
with the wood dust/shellac technique, right?
I've used the StewMac black WB grain filler quite a bit on refinishes, BTW it
looks really nice on mahogany, but I found it tends to shrink a lot over time.

_________________
Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

[QUOTE=j.Brown] Robbie's input never ceases to amaze and intrigue. I'm very thankful to learn from such an insightful instructor.
Robbie, you must have been jones'n for the OLF, you've been posting like mad since you got back.
-j. [/QUOTE]

J, are you trying to get an A out of this semester's class with all these nice compliments? Really though, thanks! The reason I have been posting so much is that I missed a lot while on vacation. It took me half a day yesterday to just read all the threads and get caught up. This place rocks!

[QUOTE=laurent] I'd like to try Behlen Rockhard varnish, would you recommend the dust/
shellac pore filling technique before applying the varnish? Will the
cheesecloth method work with it, or is it better to use a foam or bristle
brush?[/QUOTE]
sure, this method of pore filling will work. Any of the above applications methods will also work. Just find one that works best for you.

That is correct. I use a water based paste pore filler that had been dyed black. You can French polish over the top of that. The concern though is that you must apply your first coats very very lightly in order to not dissolve the shellac acting as a binder for the pore filler. If this happens you will just pull filler out of the pores. If you follow the instructions in my finishing dvd you will have no problem.

[QUOTE=Graham Steward] Does anyone use pumice for pore filling? I used that on the back of my first guitar(I left the sides unfilled to see what it would look like) and really like the results on the back, but it was a lot of work.

I'm not so happy about how the sides turned out.

[/QUOTE]

On French polish I use to use pumice fill exclusively but have switched to Zpoxy finishing resign for darn near everything. Pumice fill is a good bit of work and requires a learned technique. But it is the traditional fill method for French polish. Heck I remember my grandfather using pumice as a dry abrasive. Just sprinkling FF and FFF on the surface then rubbing with a hardwood block on tables he built. Talk about a lot of work.