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Hi, I'm currently brush finishing my 3rd and 4th acoustics (mahogany & European walnut respectively) with KTM-9 water based lacquer following the method provided on the LMI website. I have opted to avoid the pore filling step by building up and sanding back the layers of lacquer finish until the pore pits disappear. The mahogany has had 10 coats and so far everything seems to be looking fine.
Now I probably should have asked before I went ahead with this method, but what repercussions does anyone envisage/has anyone experienced here? Will the porous nature of the wood allow the lacquer to soak too deep into the wood thus dampening it more than if it were layered on a pore filled surface? Or is the pore filling step simply a measure to avoid having to apply extra coats and then sand them back?
Thanks in advance for any comments. Caspar.

over time the finish still shrinks . Filler doesn't shrink and keeps the finish coats from sinking. If you want that perfect finish you need to give the finish more than ample time to cure and shrink. That is why it is a finish and not a filler. Over time the sinks will show

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Finish shrinks as it dries, and it takes many weeks to stop shrinking. It will keep shrinking back and making the surface rough. Also, it's taking you a dozen coats w/sanding to fill the pores. I pore fill with Timbermate, usually fill on the first pass, and because it dries so quickly I'm completely done in just a couple of hours, start to finish (and most of that is drying time).

I don't know how much the KTM is going to shrink but if I was looking to do a really great job, I might be tempted to add a couple more coats (without sanding) and let it sit around for several weeks before continuing. That will give it a chance to shrink back. After that happens, sand it back. If you keep sanding it back now, you'll never get the pores filled like this because the finish will always shrink below the surface again.

Your method will work but it's a rather long and drawn out process of filling pores, probably taking months for the finish to truly sink back. There are much faster and easier methods.
This is the method that I use:

http://www.classicalguitardelcamp.com/v ... hilit=pore

Using finish material as filler is rather expensive ..... just saying.

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You also run the risk of getting the finish too thick from applying all those coats which can lead to crazing and other film failures.

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Ok many thanks for the advise. I will go ahead and let the finish cure a couple of weeks then see how much it has shrunk back and go from there. Looks like I'll be going back to the pore filling on future instruments! I used the LMI acrylic paste filler in the past with satisfactory results. How does Timbermate compare? Is anybody using similar products that are available on this side of the Atlantic?

You have tried to get Timbermate this side of the pond too! There is something with that name but it's not the same stuff. I even emailed the Australian company without success. That's when I had the idea of combining the Gypsum and the two binders. Gypsum has a long tradition in being used as a wood filler. Providing the two applications of this filler are used a few days apart I don't think that there is any problem with shrink back.

http://www.stewmac.com/shop/Finishing_s ... iller.html

They ship internationally, no problem.

You can just buy the big tub of the natural color (it's sort of a greyish white), and then stain it to whatever you wish with Transtint dye. If you do that, it becomes very important to seal the area before staining so the transtint doesn't stain the wood.

Hi Caspar ... you could try this stuff :

http://www.applegate.co.uk/listings/sto ... 57956.html

I actually ordered mine from the USA before I found this site. Crystalac works nicely, it takes a few coats but is a damned simple, reliable and colour free way to fill pores

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I've had bad experiences with almost every pore filler I've tried, including pore o pac (or whatever it's called), from Behlen, an LMI water based one, flooring filler, and a few others I think. Maybe I just don't like the process much but it seems to cloud out or otherwise do something bad to grain clarity, and I'd rather have it slightly porous but natural looking. I probably need to do it right next time.

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Like stated before, finish shrinks over time. However, Mahogany and Walnut are not too porous to begin with, so the effect might not be as bad as, say, Wenge.

Call me old fashioned, but after trying many pore fillers, I always reach for old-school pumice. Cheap, looks better than any other, IMO, fairly quick, and 2 passes are usually enough, even on Wenge.

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I like Z-Poxy Finishing resin as a pore filler. It reallt wets the wood and makes the grain pop. I have not experimented with anything other than TimberMate and Z-Poxy but I like them both. Z-Poxy just makes the wood look better in my opinion. And, since it was formulated to adhere to nitro, I should not have any issues in the future with adhesion. I find it to be pretty fast. I can do two coats a day and it usually only takes 2-3 applications to fill the woods I have used so far.

I have found that nitro can continue to shrink back for up to a year. Especially if you use the lacquer as a pore filler. My #1 was perfectly flat like glass when I was done sanding and buffing. A year later and pores were showing. Two years later and it looks like I did not pore fill. Live and learn, eh?

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I agree with Tony on Z-Poxy. It really highlights the wood grain, doesn't shrink significantly, and is very easy to use. One application to fill the pores and another thinned coat, quickly wiped on, to cover any sand-throughs. Done.

+1 for Zpoxy. I apply the 1st coat thinned as it seems to soak in a little deeper and makes a sand through easier to even out. The last one I did all coats were thinned and padded on like a french polish and the sanding back was much less effort as the application was evener. It took 4 coats to get good fill and actually had no sand through.

Fred

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Fred, what's your mix for doing it like that?
thx

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Milton, ON

Shellac and Pumice, or LMI's micro-bead filler. I don't like epoxy anymore due to inconsistent results from mixing, and it's messy stuff and the smell isn't pleasant either..

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I just do it by eye, probably about 1/2 the epoxy volume of alcohol. Thin enough to pad on easily.

Fred

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Same here.

I'm finishing a white oak guitar now, shellack and pumice and I keep asking the question too, why pore fill!

+1!

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Reguardless of material chosen, if you're having trouble pore filling you're probably either bridging the pores, instead of getting the filler down into the pores, or your sanding too hard after filling, sanding into new pores. The majority of the guitar buying public want a slick, smooth, shiny guitar.

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One thing I have noticed is there are so many alternative methods and I think we are all seeking the magic formula that makes it easy to do and fool proof. Too bad that we never seem to get there.

Fred

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In the thread linked below I describe a different method for using Z-Poxy to pore fill. It works very well IMO and others have had success with it as well. Last time I did it I used one coat of unthinned epoxy and one very thin wash coat. VERY little sanding required because virtually all of the excess is scraped off before it cures. It has worked so well for me I just don't see ever using a different material.

viewtopic.php?f=10101&t=32482&hilit=Epoxy+blade

what do you mean by sand through?

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"Preoccupation with an effect gives it power and enhances the error"
from "Your Owner's Manual" by Burt Hotchkiss.