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Question about pumice pore filling
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Author:  Alain Moisan [ Tue Oct 15, 2013 8:46 pm ]
Post subject:  Question about pumice pore filling
Hi all.

I'm getting interested in French polishing (it's about time, I know...) and as I read and view the different video tutorials on Youtube, it makes me wonder why we aren't all using pumice to pore fill regardless of the finishing method? It seems quite easy to do and requires no heavy sanding to level things down afterward. So I assume there must be a down side. Which is it? Too long of a process? Shrink back issues?

Thanks!
Author:  WaddyThomson [ Tue Oct 15, 2013 9:08 pm ]
Post subject:  Re: Question about pumice pore filling
Maybe because it's labor intensive. It works though and it doesn't take that long. Getting the feel of it is the hardest part. Working alcohol and pumice with a bit of oil and, in some cases, a tiny bit of shellac is a tricky process without getting too much build up in some areas.
Author:  Tai Fu [ Wed Oct 16, 2013 4:44 am ]
Post subject:  Re: Question about pumice pore filling
It's a really good workout... Took me hours to just do the back on a jumbo. Also I've found that lacquer doesn't stick as well to shellac as I thought, because I had a neck that was pumice filled long ago that peeled.
Author:  Alain Moisan [ Wed Oct 16, 2013 8:17 am ]
Post subject:  Re: Question about pumice pore filling
WaddyThomson wrote:
Maybe because it's labor intensive.


Maybe so, indeed. But so far, all the different pore filling methods I've tried have been pretty labor intensive as well. Sanding/scraping epoxy to bare wood on an entire guitar is something I could do without...

A side track question: does using the pumice method tends to stain pale wood that is beside a dark one? (I'm thinking pore filling a rosette, for example...)
Author:  Tai Fu [ Wed Oct 16, 2013 8:22 am ]
Post subject:  Re: Question about pumice pore filling
Yes you can, so protect it with shellac and I generally sand back anyways to get rid of the build up and clean up all the stained wood. I find it difficult to not stain pale bindings when french polishing, not sure how people avoid staining rosettes.
Author:  Alain Moisan [ Wed Oct 16, 2013 8:39 am ]
Post subject:  Re: Question about pumice pore filling
Tai Fu wrote:
Yes you can, so protect it with shellac...


Thanks Tai.

But for what I understand of the pumice method, shouldn't there be a few coats of shallac already applied when pore filling? Wouldn't the alcohol in the pad disolves the shellac anyway and cancel any protection it was intend to procure?
Author:  Tai Fu [ Wed Oct 16, 2013 8:50 am ]
Post subject:  Re: Question about pumice pore filling
the hope is the shellac will at least provide enough protection to prevent the stain from soaking into the wood grain so that when you sand it back, you won't have to sand real deep to reveal clean wood...
Author:  Alain Moisan [ Wed Oct 16, 2013 8:58 am ]
Post subject:  Re: Question about pumice pore filling
Tai Fu wrote:
the hope is ...


Hmmm.... Not good. Giving the fact that staining around the rosette pretty much makes an otherwise perfect guitar unsellable, hope is not enough for me! I must be sure it won't stain.

I guess I'll leave pumice for the rest of the body, and just use something safer for the rosette.
Author:  jfmckenna [ Wed Oct 16, 2013 9:03 am ]
Post subject:  Re: Question about pumice pore filling
The idea is to wipe the dark woods with shellac so as to protect them from staining but I have always had problems. I use CA to fill rosettes.
Author:  Tai Fu [ Wed Oct 16, 2013 9:05 am ]
Post subject:  Re: Question about pumice pore filling
Well, in that case fill the void with medium CA. The rosette shouldn't be that much of an area and CA does a pretty good job of filling voids in inlays and rosettes. Just coat the area with shellac to prevent the CA from staining the top.

I generally would only pumice a large area that needs filling such as backs and sides. The shellac protects the binding so that if you do stain it you can sand it off.
Author:  WaddyThomson [ Wed Oct 16, 2013 10:05 am ]
Post subject:  Re: Question about pumice pore filling
Egg white is another way to help put an additional protective layer on the purflings and rosette. I have had less issue with rosettes staining than with purflings. One thing you can do is polish a couple of sessions around the purflings before the filling process. It adds some protection, and the filling still works. CA is a good way to fill rosettes, after a couple of spit coats of shellac have been put on the top.
Author:  Alain Moisan [ Wed Oct 16, 2013 10:17 am ]
Post subject:  Re: Question about pumice pore filling
Thanks guys. I have ways to fill the rosette, that's not an issue. It just seems that I won't be switching to pumice anytime soon, that all!

Waddy, I'll give it a try with the egg white. I wonder if alcohol can disolve it?
Author:  Nate Swanger [ Wed Oct 16, 2013 11:03 am ]
Post subject:  Re: Question about pumice pore filling
Waddy really helped me a lot when I was learning. I probably redid the filling 3+ times just trying to get the right combination of oil, shellac and denatured so that it filled without leaving to much junk on the surface. Once you figure it out though it clicks. I'll probably always do it to fill pores now, not sure if ill do keep using French polish or not, probably if I build another classical but for steel I’d want something a bit harder, my top is pretty scratched up from finger nails.

I used stick shellac to seal my rosette, it worked ok. Purfling didn’t fare so well, I may try the same method next time. I did several coats with just shellac but it never really did a good job at sealing. Rosewood seemed to just bleed out, guess it’s somewhat dependent on what you used. I saw a how it's made on supercars and they showed how they do pin stripes on cars, tinny little tree rat paint brush, i may make myself one next time I’m out in the woods. :twisted:

In the end i didn’t really mind the maple purfling taking a bit of tint, it actually matched the color of the top. Nice when boo boo's turn out in your favor.

Nate
Author:  Alain Moisan [ Wed Oct 16, 2013 12:12 pm ]
Post subject:  Re: Question about pumice pore filling
Thanks for your input Nate.
Author:  Greg B [ Wed Oct 16, 2013 12:24 pm ]
Post subject:  Re: Question about pumice pore filling
Alain Moisan wrote:
WaddyThomson wrote:
Maybe because it's labor intensive.


Maybe so, indeed. But so far, all the different pore filling methods I've tried have been pretty labor intensive as well. Sanding/scraping epoxy to bare wood on an entire guitar is something I could do without...



Paste filler is much, much faster than either epoxy or pumice fill, but for some reason it seems to be out of fashion. The transparency and extra depth of epoxy or pumice fill is nice, for sure, but you have to pay in labor.

On furniture, you would use pumice by flooding the surface with oil, and then rubbing it in. Needless to say, this is faster, but pretty much no one wants to do that to a guitar.

Egg white fill has a particular look to it that is pretty easy to spot. I think it would look wrong on some instruments and right on some others.
Author:  WaddyThomson [ Wed Oct 16, 2013 1:02 pm ]
Post subject:  Re: Question about pumice pore filling
Not talking about egg white fill, though it works just fine. Just sealing with egg white before putting any shellac. It does raise the grain a bit, so light sanding with 400 grit is not a bad idea after sealing.
Author:  Tai Fu [ Thu Oct 17, 2013 8:04 am ]
Post subject:  Re: Question about pumice pore filling
I can't get paste filler, at least not the oil based paste filler that won't shrink. All I can find here in Taiwan are latex based paste fillers that for some reason sands like rubber, but I saw Robbie O Brien talk about using spackling paste as paste filler after tinting it to the right color...

I just found something that works with pumice filling to prevent staining the binding: Tape the binding/purfling off before pumice filling, and it keeps the stain away from the binding and once you tear the tape off when you're done filling, the binding stays white and then you can just sand off whatever that butted against the tape. After that do a couple of body sessions in the dark wood (avoiding the binding) only, then move onto the binding. This will keep the binding clean.
Author:  ernie [ Thu Oct 17, 2013 9:03 am ]
Post subject:  Re: Question about pumice pore filling
In the early 80/s I was using oil based paste filler and learning to control using it by thinning either with mineral spirits or naptha,Since I was refinishing large furniture tops it made sense , I would seal with shellac , and then use a thinned down varnish.In instrumentmaking I have been using a water based paste filler.Which frankly IMHO dries too quickly . I bought some behlens oil based paste filler at woodcraft. With the oil base . you can use a variety of different coloured pigment based oil stains to colour your wood before applying the sealer and finish coat.There was a book out in the early 90/s by a famous hungarian wood finisher who used this to great effect.Think the book was called adventures in wood finishing by george ??
Author:  jfmckenna [ Thu Oct 17, 2013 9:26 am ]
Post subject:  Re: Question about pumice pore filling
I have been using egg whites as both a sizer and a filler. It's a lot faster than pumice. I will touch up spots with pumice though. I don't think the alcohol has any affect on it. It dries pretty hard and fast too.
Author:  Alain Moisan [ Thu Oct 17, 2013 9:36 am ]
Post subject:  Re: Question about pumice pore filling
jfmckenna wrote:
I have been using egg whites as both a sizer and a filler. It's a lot faster than pumice. I will touch up spots with pumice though. I don't think the alcohol has any affect on it. It dries pretty hard and fast too.


Thanks for the info. My tests with egg white as a pore filler didn't go too well with regards to staining pale woods, specially spruce or cedar. When sanding with the egg white where there was both dark and pale wood (like the rosette, for example), the dark slurry burried deep into the spruce fibers and made an ugly mess. That said, I didn't seal with egg white first...
Author:  jfmckenna [ Thu Oct 17, 2013 9:45 am ]
Post subject:  Re: Question about pumice pore filling
Alain Moisan wrote:
jfmckenna wrote:
I have been using egg whites as both a sizer and a filler. It's a lot faster than pumice. I will touch up spots with pumice though. I don't think the alcohol has any affect on it. It dries pretty hard and fast too.


Thanks for the info. My tests with egg white as a pore filler didn't go too well with regards to staining pale woods, specially spruce or cedar. When sanding with the egg white where there was both dark and pale wood (like the rosette, for example), the dark slurry burried deep into the spruce fibers and made an ugly mess. That said, I didn't seal with egg white first...


Ah yeah I only use it for backs and sides. But that is exactly how it works is like pumice it tears fibers and just sticks them into the pores and essentially glues them in so if you are in a border light dark area it's not easy to get it right, so I just avoid that.

I use the Milbourne FP technique and he swears by 5 minute epoxy now. I will probably try it one day but I just don't like epoxy and if I can avoid it I will. But it supposedly works quite well and I think he just uses the cheap stuff.
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