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Just curious how you prep your guitars prior to finishing. What grit do you start and end with? Do you use sanding blocks? Cushioned or hard? Do you use a ROS at any time? Any other tricks?


Thanks
Richard

Prior to sealing and finishing I use an air powered ROS with P grade 150, 180 and 220 paper. I use Norton from my local auto body supply.
I use KTM SV and level sand before the 2nd days coats with P 800. My final leveling is done with P 1000 and 1200 two days after the final coat is sprayed.
Anything I can't reach with the ROS I do by hand with a shaped block.

I sand out by hand with cork lined blocks. I prep to 180 before sealer under nitro and poly. I'll go to 220 on a FP with woods that do not need grain fill, otherwise 180. What grit to start with will depend on the type of wood and how cleanly you work. I generally do 120 , 180, clean & seal. Cleaning after sanding is just as important as the sanding. The final sand is always sealed immediately, wood will begin to oxidize rather quickly and for best adhesion you want nothing between the finish and the wood. If I could not seal in less than 36 hrs. I would re-sand prior to sealing. Most finishes fail before the can of finish is ever even opened. Prep is very important. Sand too fine or burnish the wood and the finish may not stick long term. Leave dust on the surface and it may cause all types of problems as well.

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

For me Naptha is trump. It's amazing the scratches that show up after you think you've gotten it perfect.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Is it benificial to do a wipe down with pure alcohol for example, to raise the grain then sand smooth before aplying fillers?

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Phil

http://www.oleninstruments.com

"Those who tilt at windmills are only considered insane by those who can't see the dragon."

I've got a newbie question: is it ok to fill the pores of the soundboard with zpoxy (or whatever) or does this compromise tone/volume?

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Doug

Don't let fear or common sense stop you from trying to build something

Doug:

Spruce and cedar do not have significant pores, therefore filling is not necessary.

I just raise the grain, final sand and paint.

Good luck,

Mikey

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The Biggest Little City, Nevada
www.hammondguitars.com
I love building guitars!

I like to get the drum sander marks out after the plats are joined before building begins. ROS with 120 on top back and sides, build the instrument,
ROS back and a combo of ROS and hand sanding the sides with a cork lined piece of flat wood up to 320 (gold paper: 150,180,220,320 )
Neck and headstock is sanded by hand to 320
save the top for last: very light ROS with 180, then by hand with sanding block up to 320
wash coat the top with 4 coats of shellac applied with inner pad
pore fill back/sides with jointing compound dyed black, sand back with 320, two cycles or three if pores are big
pore fill neck/headstock with mahogany dust/shellac, two-three cycles,
seal coat everything with 3-4 coats of shellac with inner pad
Sand back the top with 320, apply egg whites for sizing/starching, light sand with 320
Start the French polishing process.

This is per the O'Brien French polish process (with my own slight variations in sanding). Great DVD, highly recommended!

Interesting, i have never heard of using sheet rock compound for pore filling.

R

Works great. Exactly what sheet rock compound is for...filling voids.

As a relatively inexperienced builder, I can't add meaningfully to the recommendations about sanding, etc. I do want to underline to other beginners how important it is to check for scratches, dips, and other flaws before moving to finishing. Even knowing that these flaws were hard to find, and using naphtha or mineral spirits, I've still missed them, only to find them part-way through finishing when they are a lot harder to deal with. Darkening the shop and using just one source of light, raking across at an angle, is one technique that helps. If you're like me, once you think all the prep is over, you are impatient to see how the guitar looks under finish. This can make it harder to take the time to spot the little things that need more work. I have learned I need to detach myself from the need to rush ahead, and approach this step as if I get a lollipop for each imperfection I find. Fix each one (iron and a wet cloth for the dents, sanding for scratches, CA for tiny pits, etc.) then search for more.

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Tim Allen
"Never hurry, never rest."