Experiment with New Pore Filler from SMD

Finally got around to experimenting with that new pore filler that SMD is selling. I have high hopes for this stuff as I have never been happy with pore fillers in general, especially the dyed paste stuff that is supposed to match the wood. Just awful on mahogany making it look sort of gray. Epoxy resins are nice but so hard and the new to me method of using CA seems promising, but has its own issues. Before I put this stuff on my newest uke (gonna be a stunner and I don't want to screw it up), I experimented first.

Anyway, this stuff is waterbased and clear. It has the consistency of warm lard to my eye. The smell is solvent but not obnoxious. The directions say to apply with a brush after sanding wood out to 350. Scrap with squeegee against the grain. (I used a credit card). Let sit an hour or so and sand out with 350. Repeat process again. Ready for waterbased laquer in a couple hours, 12 hours needed for non-waterbased synthetics (nitro etc.). It says no pre-base is needed so I put it on raw wood. This was against my instincts, but I followed directions.

I used three types of wood: Mahogany, myrtle and redwood. I'm not sure myrtle or redwood even needs a filler, but I threw them in there as controls for the mahogany. I'm going to let the stuff dry overnight and will put on a single uncut coat of lacquer tomorrow. One area is treated and one area is not treated. Stay tuned. Pictures below. Unfortunately it is difficult to photograph wood pores, but I did the best I could. Will post pictures tomorrow of lacquer over both area.

The stuff:



Test woods with two coats:



Mrytle treated sided on left, side on right untreated



Mahogany. Note that it significantly darkens the wood.

I have some of this and have not given it a try. I worry that it will shrink back and that could take some time. The StewMac description says it doesn't shrink but.....
I'll have to give it a try on some scrap and see

Put the finish on and see what it's like after a couple of months. I kind of prefer the slightly sunken pore look but I'm probably in a real minority.
There are a few 'factors' regarding pore fillers. Namely how easy is it to apply, how fast it diries/hardens, how much it shrinks and how 'natural' looking it is to the wood that you are filling.
Many pore fillers fail on the last but that might depend on how fussy you are. The most natural looking fillers that I've used is clear shellac but it takes a long time to fill pores. CA or epoxy may give similar results, although I've not tried those.
I'm not overly fond of paste fillers, the type with added stains.
The one that I have been very impressed with is one that was used by furniture makers of past. Fine pumice is sprinkled on to the surface of the wood and pushed into the pores with your palm. Oil (I use Danish Oil) is poured over this and then the slurry is worked into the pores. It only really fails on the drying/hardening time but if you have the patience it's a fuss free, simple method and not quite as messy as some.

Follow-up to yesterday's pore fill. The stuff set up quite hard overnight and sanded out well. Gave a very smooth surface. I put on a single coat of KTM-9 (self-crosslinking polymer from LMI), let it dry and sanded out to 350. Looks good and I'm going to try it now on an instrument. I tried to take pictures but they don't show the pore surface well at all. Turned out better than shown. Pore fill on left and raw wood on right.

This looks very similar to "Crystal-Lac", a filler I used many years ago. It dried very hard and sanded well. Many of us have had better success with the addition of cabo-sil, (silica micro balloons) to increase the solids content. It worked very well of a short period of time but as has been mentioned here earlier that time will tell whether it's a good filler or not. I always found significant shrink back after 6 months to a year. Of course it all depends on what degree of flatness you want to achieve. Some builders feel that some shrink-back is acceptable while others try to achieve a perfectly flat surface. I don;t think there's any right or wrong, just a matter of personal preference.
BTW, Make sure you also check for lacquer adhesion. In my testing I would follow the exact procedure as I would for an actual instrument (ams number of coats, sanding, drying time, etc.). Good luck in your trials and thanks for sharing with us.

Thanks Chuck. Will report back if there is "significant shrinkage" in the future. Only time will tell.

This stuff is so easy to use. I've thinned it and applied as directed. I think you can sand out after 45 minutes each coat then wait for it to cure. Will take the effort out of sanding after it has fully hardened. using my Wurth lacquer finish tomorrow. Will return and report.

I tried thinning the filler and found it needed three applications for koa. However if you sand after 45 minutes the whole process takes no time. The finish was a bit variable on some rowey mahogany I used for a neck making patches of milkyness in certain lights. I sprayed over it a matt finish. My next experiment will be to use a water based stain to colour the filler. So far, pretty impressed with the ease and speed using this stuff. It takes no skill to apply and seems consistent.

Pete Howlett said:

The finish was a bit variable on some rowey mahogany I used for a neck making patches of milkyness in certain lights.

Click to expand...

I am also getting some subtle patchiness and milkyness with the stuff on mahogany. Works a charm on other woods. I'm suspicious the fault lies with my latest batch of "mahogany" which I'm not happy with. I have no idea where the !#&%!?! came from, but it sure as hell wasn't Honduras. Anyway, as the finish cures out the slight milkyness is becoming less apparent.

Pete Howlett said:

I tried thinning the filler and found it needed three applications for koa. However if you sand after 45 minutes the whole process takes no time. The finish was a bit variable on some rowey mahogany I used for a neck making patches of milkyness in certain lights. I sprayed over it a matt finish. My next experiment will be to use a water based stain to colour the filler. So far, pretty impressed with the ease and speed using this stuff. It takes no skill to apply and seems consistent.

Click to expand...

If you thin it with water I'm pretty sure it will shrink even more in time. Those of us who were using a similar material years ago were making it even thicker with the addition of silica. It still took three coats and after a year it sometimes looked almost like no pore filling was done at all. It was frustrating to spend all that time only to have the pores show through. The shrink-back is more apparent with thin lacquers. One fix around that problem is to load the instrument with lacquer. But who wants to do that?

Gork's Goodfilla has a new water based clear filler that will be available in four weeks from Stew Mac. I talked with Barry (owner) about it and he said it was water clear with zero shrinkage. It can also be tinted. Sylvan Wells absolutely loves the stuff and has been doing trials with it. As with everything, I'll get some and suss out if it's any good. See me in the spring after the New England winter. I too am looking for an alternative to using CA.

Would it work to mix just a bit of super fine sawdust in with the clear filler to reduce potential shrink back? I know you guys who do this for a living don't like to experiment and would rather buy something that works, but may be worth a try on some scrap.?

The Cardinal grain filler from LMI is good too.
The "rosewood" version is basically black.