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After applying 2 spit coats to the spruce top of my classical I noticed a ding and some areas that need sanding at the edge of the lower bout. I fixed them, and after sanding off the initial spit coat I reapplied a new spit coat to the area and went on to FP the top.

I've completed a few bodying sessions and now I'm noticing a lighter band that appears at certain angles in the area that was sanded.

Is it time to take it down and start again?

I would because it is likely to stay this way since the shelac is now sealing the wood. I would sand again and this time sand the entire top lightly to even out the color.

Surface prep prior to starting any finish is key. Hesh is right the previous spit coats sealed the top. now you have sanded back to wood to sand out a ding (should have been steamed out first then leveled the raised grain left by the steaming rather than by sanding the area to the dings level) the newly applied spit coats are sealing the bare spots but adding depth to the rest of the area therefore the refraction of light of the two different areas will vary.

One deep nick needed filling and there were sanding marks I missed. I did steam out the dings, filled the nick, sanded, raised the grain twice etc, and re-applied a spit coat to the area I sanded.

I'm not new to finishing guitars (I usually spray lacquer), just new to FP - but thanks for the advice.

I just heard of using egg white as a size/sealer.
I haven't tried it myself but apparently its traditional.
Formerly used by rennaissance lute makers, and still used by some guitar makers.
Im told that egg white or "glare" raises the grain, seals, stops colour from running, adds warmth and sparkle, prevents sinking of subsequent coats.

Try it on a test piece, straight without diluting.
Brush it on, leave it cure over night, and then give a gentle fine sand before French polishing.

Claire

Yep Claire egg whites sounds like a great solution. A number of OLFers have used this method, Colin S. for one, and there are some discussions regarding using egg whites in the archives.

I am always very impressed by the minimalism of vintage methods and how well they indeed did work.

Sorry Mike! But you only mentioned sanding to fix the dings so i assumed that was what you did. Even with Nitro you would have this refraction issue if you had sanded back to bare wood, resealed the sanded area and then began finishing.

Hesh is right as well about sizing the top prior to starting the finish. I will also make the top less susceptible to minor marking during the FP process.

No worries...I left out many of the details to try to keep the post breif.

I'm going to try the egg white sizing/sealer on some offcuts I have from the top and see how it looks. I originally followed the Millburn method with good results, using shellac as a sealer, covering the rosewood bindings (and rosette) first so they don't run. I finished the headplate and it looks very nice, the sides and back have had a few bodying sessions also, and it's looking good.

Last night I took the top finish down with DA soaked paper towels followed by wiping (I read that here, worked great), and then sanded through to 400 with two grain raisings. It's ready to go as soon as I decide if I want to use shellac or egg white as the sealer.

Thanks again everyone for the advice.

Sizing is not the sealer, two different processes Sizing stiffens the grain. you will still need to spit coat after the sizing is done to give the body sessions something to amalgamate to.

Sizing with egg whites, the egg whites is somewhat absorbed into the raised fibers of the Spruce or Cedar causing the fiber to expand and dry harder than it would be un-sized. But this is not a sealer in of its self for French polish. You still need spit-coats prior to starting body sessions

If you are a child of the 50s-60s you may remember when your mom used a non-starch stiffing solution when she ironed your jeans to make them some what stiff and hold a crease. This was called sizing. Pretty much the same thing as sizing a top wood with egg whites.

Thanks, for the clarification Michael, I didn't know that. The shirt starch reference does ring a bell.