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I have read that some people use egg white as a "sizing" on the soundboard before applying the finish. So I tried some egg white on a scrap piece of spruce and then FP'd it to see what difference it makes.

The egg whites raised the grain a lot, and it took three iterations of applying egg white and sanding down to get it smooth and even. The FP builds faster, but apart from that I don't know the benefit is supposed to be.

Does anyone have any insight as the the value of egg white sizing on the soundboard? And, can you glue the bridge on over the egg white, or should that area be masked off?

Thanks for your thoughts...

Bart

Yes you can glue over the egg white. It does act as a sealer and helps in a similar way to starch on a shirt. Once sanded back it makes fir a smoother top when finished with less variability between hard and soft wood as I understand it.

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Waddy

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Sound Clips of most of my guitars

I use an "egg wash" to stop color bleeding from the rosewoods into the lighter spruce as well as the maple and holly purflings when I apply the first "spit coat" of FP.
This can be a real mess and difficult to recover from if you ignore this problem.
E.I Rosewood is particularly bad, Brazilian less so but a clean result is much easier to achieve using the egg wash than without.

Thanks, Waddy and David.

David - good to know that the egg wash will stop rosewood bleeding into lighter woods. By "wash", do you mean that you thin the egg white with water?

No water.
I simply use the most liquid part of the white from several eggs.
Use a soft brush to apply smoothly, flowing it over the entire guitar. Avoid whipping it into a froth which may cause a bit of a different look to the final finish in those areas.
Let it dry 24 hours.
I usually "pre-raise" the grain by moistening the top with water, drying and final sanding before applying the egg wash.

David, do you sand after the eggwash and do more than 1 coat, or is it just pre-raise the grain with water, sand, 1 coat eggwash, and then proceed with french polish?
Thanks, Wendy

Pretty much as you describe it Wendy.
Maybe an extremely light swipe with 320 if there is still some grain popping up, but, because I sand between bodying sessions everything will get leveled out as I go.
The one thing you don't want to do is to break through the egg wash coat by sanding.
And it's just one application of the egg wash then allow to dry 24 hrs then spit coat and proceed to FP.