Sealing a guitar before a refinish - paint edumacation

[HAMERMAN]

I am converting my lefty RG550 into a JEM clone. The original finish had several large chips down to bare wood so I removed all of the original finish using a heat gun. I will soon add the monkey grip (I am still on the fence about the loins claw).

I have a good friend who will paint it for me using auto paints. I don't jack about paint so I am not sure if that means Poly or Acrylic or somethign else as a class of paint. Figuring that out is probably a good first step. Once that is figured out knowing what I can and can't use will be important to know. For example - assuming auto paint is Poly can poly paint go over sealer intended for lacquer?

Before it goes for paint I would like to do everything I can on my end to ensure good results. Once I am done sanding I figure I need to seal the wood and perhaps even add a primer coat. I have no idea what to use. I did a bit of poking around at Stew-Mac, Reranch and Luthiers Mercantile and virtually all of the producys make reference to a lacquer finish which this will not be. I haven't a clue what is and isn't compatible so I don't know if these products are OK to use or if I need to find something else.

Do I need grain filler or is that only for transparent finishes?

If I do need grain filler does that go on first or is it after a base coat of sanding sealer? Do I need a special poly compatible filler?

What is my best option for sealing? Do I need a special poly compatible sealer? (From what I have read Fullerplast sounds ideal but I get the feeling it's not the kind of thing you can buy in one or two guitar quantiites.)

For arguments sake if I had a chip that was too deep to sand out what should I use to fill it and when would be the best time to use it in relation to other steps? (Over grain filler but under sealer etc.)

Do guitars generally have a primer coat? If it's an optional thing I would still like to add one since that would be my best chance of spotting any problems before I hand it off to my friend.

I have several other guitars that I plan on refinishing so I really want to do this the right way. Any and all advice is welcome since this is all new to me. FWIW authenticity to a factory finish is not a concern - I just want an attractive durable finish given what I have to work with.

[zenmindbeginner]

I'm just a layman, but I too have done a good bit of research into the subject like you have.

The grain filler and sanding sealers fall into two categories; water based and oil based.

The key is to stay all water based or all oil based. Poly or nitro will go over water or oil based varieties no problem. I think that the issue is combining an oil based filler with a water based sealer and visa versa.

Also, water based fillers and oil based fillers act VERY differently and have much different drying times. Water based fillers aren't as messy as the oil based variety and won't kill nearly as many brain cells. They also dry hard as a fookin' rock and you don't have to wait for the solvents to fully cure very long at all before you start the finishing.

Oil based fillers are a lot more easy to work with in the application process and are very easy to take off once they dry. You can basically whistle while you work and have a fun time of it. The water based fillers will be a bitch to take off (requires actual sanding if you wait too long), I'm just warning you ahead of time. The oil based dries really slow and you can just whisk the excess filler off of the body with some burlap cloth.

The oil based fillers are not available at Lowe's, Home Depot or ACE... you will need to order them from Woodcraft or a similar store. McFadden's or Behlen's are the ones that people use the most.

The oil based varieties seem to have less problems with finish adhesion than the water based kind FWIW.

Some people seal before they fill and some seal afterward... I think it depends on whether or not you want a stained finish or not. Many guys stain first and then seal it, it all depends on a transparent or opaque finish and what look you are trying to achieve. If it's an opaque finish, you will probably apply the sealer after you fill.

But...

Do you even need grain filler? What kind of wood is it? If it's an alder body, you don't need to fill the grain. Hell, you could skip the grain filler and apply a dozen or so sanding sealer coats and the grain will fill up nicely. Ash will need to be filled, but I think many guys just use a several sanding sealer coats for that. Grain filling is mainly for mahogany since it is a VERY porous wood.

The more porous the wood, the more it needs grain filler. Maple is basically hard as a rock and needs no filler, neither does alder or basswood. Ash and Mahogany require the grain to be filled.

You took the paint off with heat? Did you burn the crap out of the wood in places?

[Stike]

You should seal it but I wouldn't use a lacquer based sealer under automotive paint. You'd probably be best off having your friend shoot a couple of coats of 2K or epoxy sanding primer. Let that dry a few days and block/level sand with 320-400 grit and then let him do his thing from there unless you sand through to wood and you'll need to spray some more primer.

If that isnt an option you could use an easily available product called Polycrylic. I have not used it but I know vintage guitar nut Curtis Novaks uses this now instead of Fullerplast. Curtis sprays lacquer but in theory it should work under automotive paints once cured. It will need to be sanded since there will be no chemical bond with the topcoats.

I'm guessing your Ibanez is basswood? No grainfiller needed. For your deep chip use wood putty and do it under the sealer.

[HAMERMAN]

Thanks guys!

It is basswood so good to know no grain filler needed.

I will be talking to my buddy tomorrow so I will ask about 2K and sanding primer.

Is this the right Polycrylic:

Minwax Polycrylic