Spray shellac before grain fill?

Red Rhombus

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I'm redoing a finish on an ash body guitar because I'm heavy handed when spraying instead of light coats.
I've sanded down to bare wood and block sanding with a 5" x 3" slice of marble counter top. Finished 180 grit then will do 220 > 320. Now, should I spray shellac before grain fill or just grain fill and continue on?
I did not shellac the first time. Just grain filled several times before primer. I'm using Goodfilla water based.

Thanks
 

jfgesquire

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What kind of finish was on the body before you sanded? Did you sand that much wood that you removed the top layer of wood that was already sealed and filled?

I used shellac before grain fill and had excellent results, but that was on ash that never had finish on it before.
 

BamaSurf

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Good question... I am redoing a Fender Hwy 1 Telecaster...although it had nitrocellulose paint it didn’t amount to much because of the sealer that Fender used. I sanded down through the sealer to bare wood... if nothing else it weighs less now
 

snarf_nyc

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yes this is pretty common to seal before grain filler. The grain filler won't stick everywhere and should stay in the grain when wiped off. If you don't use filler, you basically have to sand the grain filler off the whole body, it can be messy, and you may need to add more filler anyway if you miss a spot.
 

Red Rhombus

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What kind of finish was on the body before you sanded? Did you sand that much wood that you removed the top layer of wood that was already sealed and filled?

I used shellac before grain fill and had excellent results, but that was on ash that never had finish on it before.

Yes I believe I sanded down through the first grain filler. After the first paint attempt I could see the grain and realized I didn't sand well. Now all the little grain dips feel smooth. I will shellac first when I 'm done with the 320 grit.
 

Freeman Keller

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Red, a lot depends on your finishing products and the effect you are after. If I'm finishing porous wood I always pore fill first. If I'm doing any staining I might stain before the pore filler, most of the time I don't do both. Sand the pore filler level with the wood leaving the pores filled (duh). I may apply one more highly thinned coat of my pore filler (I use a finishing resin called Zpoxy) - that last coat is intended to be a grain enhancer.

If I have used any product that might migrate into the next application I will seal it with either shellac or vinyl sealer. Shellac is kind of the universal sealer, it sticks to anything and almost anything sticks to shellac. It adds an amber cast to the finish that might be desirable. I have absolutely no luck spraying it, normally I will either brush it on or wipe as in French polish. Most of the time I use vinyl lacquer sealer instead of shellac.

Finish coats go onto that. Remember that the cardinal rule of any finishing question is to experiment on scraps. Other pore filling products will react entirely differently than the ones I use.

StewMac's finishing schedule is pretty reliable

https://www.stewmac.com/video-and-i...ish-repair/nitrocellulose-finishing-schedule/
 

jfgesquire

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Just for reference, bare wood vs. a seal coat of shellac:

20201104_092729.jpg

20201112_200504.jpg

And then whitewash over the shellac over grain fill over shellac. (Ignore the cheap neck)

20201113_223608~3.jpg
 

Red Rhombus

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Great info..Thanks. I should have mentioned that I'm doing a solid color, not stain. I'm using rattle cans and keeping it all one product maker Rusto.
 

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Wyatt

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Since I switched to water-based grain filler, I shoot a sealer coat of shellac first to keep the water in the filler from swelling/raising the grain.
 

Red Rhombus

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After a closer look it appears that there is still filler and I can feel waves in the grain, especially on the brown streaks on the left side. Back to the block and 80 grit. Really do appreciate the response. Nice to have a place to go to ask questions.
 

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Vizcaster

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I only use 80 for shaping. 100 for removing planer marks. You could get away with 120 or 150 to remove those defects. You don't need to sand out all the old filler you could just get that damaged area leveled out. And be careful, some woods have softer areas that eat away with heavy grit sanding.

In terms of sealing, it's always a good idea to use a shellac barrier when going from an unknown to a known finish, the likelihood being that the factory used something very different than you're using. Also in terms of grain-filler application, I find it an impossible chore that's sometimes easier if the wood has some sealer on it first. Try knocking the sealer back with something gentle like 400 grit (grey) nylon abrasive pads (I use Klnigspoor version of what's otherwise known as Scotchbrite).
 

oldunc

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Shellac is commonly used as a grain filler (look up the procedure for French Polish, eg). When sanded it will leave a residue of shellac and sawdust in the pores that will redissolve and set with the addition of further alcohol.
 

DrASATele

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Does shellac “breath” ?

No finishes breath, they gas off as they cure and dry. Alcohol, which is a main component of shellac, gases off pretty quickly unless very humid (70%+).
The truth about nitro lacquer is it's very similar but there's no breathing to be had. Nitro Lacquer is a form of plastic that remains soft, not porous, until fully cures and drie,s which to most of us takes a couple of months(mainly for us to buff and polish) but in truth can take a lot longer than that.
 




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