The main purpose of a filler is that of filling the pores of the timber in order to save polishing costs, both material and time.
Charles H. Hayward, Staining and Polishing, 1959
I purchased a tub of Aqua Coat Wood Pore Filler last year with the idea of using it to fill wood pores instead of the traditional shellac and pumice treatment.
I tried it on some East Indian rosewood and was a little shocked at how much rosewood color the paste picked up and I was afraid that that color would bleed into the maple bindings so I abandoned the Aqua Coat.
Yesterday, I decided to try the wood filler again on a guitar that has Claro walnut back and sides.
I applied it according to the directions that a well known guitar maker posted in a short video on how to use the Aqua Coat and the results were terrible, the paste really didn't stay in the pores.
"No wonder so many people trash this product in the woodworking forums," I thought to myself. "but this stuff has got to work otherwise the company wouldn't make it!"
So, I decided to read the directions on the tub.
The instructions state to apply the filler and "inspect to see if the grain is completely filled, then scrape or squeegee to remove excess."
I globbed on the filler until the pores were filled...
...then I used a razor scraper to remove the excess, the scraper levels out the filler and leaves it in the pores, which is where it is supposed to be!
If I had paid attention to the directions instead of listening to someone else's advice, three coats of the filler would have been enough to do the job. I ended up putting on about six coats on the back, but just three coats on the sides. I may put on one more coat to fill in the tiny pin holes, or I may not.
Another thing I did was to sand the filler down with 220 grit garnet paper, not 320 grit as recommended by Aqua Coat.
I want the shellac on the wood, not the filler. After the 220 I followed up with a 3M maroon scrub pad and made sure that I was getting wood dust not filler dust on the pad.
Very little, if any filler was pulled up during the sanding process.
One selling point of this product is I can fill the pores, hang up the guitar and work on something else for an hour while the filler dries.
I know many people want a product that all you have to do is to wipe it on and off and you have a perfect finish.
The best way to achieve a perfect finish is to take your time and work at it.
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