Yes, the title is correct! This is about using egg whites as a grain filler. Grain filling is often a long, painful, laborious process…but egg whites make things quite a bit easier in my opinion. This is a very old method of grain filling, and likely was used in the past by Luthiers and furniture makers before manufactured grain fillers were sold commercially.
I used this method a year or so ago with success, and then forgot about it until somebody on one of the guitar building forums (MLP Luthier’s corner) used it and it reminded me. There are many different methods for doing this, but I’m sharing the method that I’ve found has worked for me. I recommend you practice on some scraps first though and find the method you feel the most comfortable with – ultimately it doesn’t matter how you do it, as long as the product is a smooth surface that’s ready for finishing.
Anyways, on to the write-up. What is pore filling? For anybody who has not done this before, it’s the process of filling the pores of wood, and it’s necessary on woods that have large or deep open pores (such as mahogany) if you want to get a glass smooth finish on the surface using lacquer or French Polish. This is what I mean by deep, open pores:
Egg whites are cheap, readily available, and easy to use as a grain filler. If you ever leave egg whites in a bowl for a day or two, you’ll find they go rock hard, and dry clear. Perfect characteristics for grain filling! In order to fill the grain with egg whites, start by separating the egg whites and throwing away the yolk. Then start to brush them on your wood.
Use a reasonable amount, and cover the whole surface. Then let the egg whites dry completely and repeat this again. Let it dry completely again before moving on.
Using just a couple of drops of water (don’t use too much water!), wet sand the egg whites with 400 grit wet/dry sandpaper. You’ll find that it feels tacky. If it doesn’t you’re using too much water. If it feels too tacky, you’re not using enough water.
The wet sanding mixes sawdust with the egg whites on the surface, which are re-hydrated by the water just enough to move around as you sand. You should be able to notice that as you’re sanding, this slurry will fill the pores of the wood. When the whole thing is sanded and all pores look filled, let it dry completely (note that in the picture below, I’ve used a little too much water).
Brush on more egg whites and repeat. You’ll want to brush on a couple coats probably, and let it dry in between coats.
Once completely dry again, wet-sand with 400 grit sandpaper until level. It should still be tacky and not too wet when you sand. Let it dry, then dry-sand with 600 grit. The result:
And this is that mahogany from the first photo after grain-filling:
Proper grain filling will save you a lot of time in the long-run. You don’t want to be spending time filling deep pores with lacquer.
Remember – “one hard day of pore filling will save you three hard days of finishing!”
The wood used in the example above was a scrap cutoff of some open grained rosewood. Just to show how well this grain filling process works, here is the same piece of wood after only two coats of nitro lacquer (wet sanded and buffed by hand):