Official Luthiers Forum!

I'm spraying my final coats of Cardinal Nitro this week in preperation for the long wait for final leveling and buffing.

Just like in building, I had no prior finishing experience, however when building, if I mess something up, I could always start over and make a new component (like the 2 necks I made on my first guitar). I understand the logistical difficulty of offering a training course for guitar finishing; need a completed guitar, the long wait times, etc., but I could sure use some help.

Courses that would be beneficial:
* proper pore-fill technique (both past and epoxy)
* proper sanding/leveling technique
* proper drop fill
* proper coverage
* proper final sand/level
* proper buffing and different methods

In other words - how to finish. I have watched quite a few on-line tuts, but there is nothing like being able to see, ask questions, and have experienced hands guide you through the process.

Needless to say, I'm not thrilled with my latest effort and would love to get some insight on how some of you have addressed some of the above in your own experience.

Steve

Robbie O Brien's video is pretty helpful for most of the steps in the process. You can borrow or buy his video courses if you need more than what LMI has for free...

It's not difficult and the key is patience and not taking short cuts. I personally don't use epoxy though because its relatively hazardous, and very difficult to sand. For big grains I use a paste filler colored to match or contrast the wood (like swamp ash).

Just keep trying, its not like pyrotechnics where a short cut could mean a trip to the emergency room or worse...

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

Patience and making sure the guitar is PERFECT between steps - no scratches from previous grit, properly leveled where appropriate, and so on - are key. Like Tai Fu says, the Robbie O'Brien DVD is pretty comprehensive, although there's a lot available on YouTube that will help you out. I'll disagree strongly on the 'epoxy is difficult to sand' front, though. Z-Poxy finishing resin sands very easily and does not clog my papers much at all.

As for 'proper' ways to do things, there are a lot of variations depending on shooting conditions, equipment, materials used and experience. My personal 'schedule' goes something like this:
- Sand to 220 or 320 grit (with the grain), making sure all imperfections are gone. I use stiff cork blocks or chunks of eraser as sanding blocks.
- Pore will with Z-Poxy (Todd Stock's YouTube videos are very comprehensive and all you should need)
- Spray finish (how many coats, pressures, tip sizes, thinning depends on too many factors to list in a 'short' way), laying down just 'wet' coats for Nitro
- Drop fill and level sand at the start of day 3 (after 6 coats), P800 wet-or-dry (lower if orange peel, but no less than P600). Basically shoot for a dull, matte surface, but don't worry if it's not totally perfect at this point. Don't sand through!
- Drop fill again if needed.
- Shoot 3 more coats (1 day)
- Level sand (P1200 if it's level enough, otherwise P800. Should be perfectly smooth now.
- Shoot 1-2 light final coats
- Straight to power buffing

I will say finishing remains by far my LEAST favorite part of building. Love the results, really don't like the process. But farming it out is not cost-effective for me (would double the cost of many of my instruments).

After a quick google map check, I know it's a long way but you're about 2 hours from Santa Cruz where Addam Stark is. Maybe you could look him up (Facebook page info https://www.facebook.com/pages/Addam-St ... 28?sk=info ) and see if you could spend a day there learning a few things....

_________________
My Facebook Guitar Page

"There's really no wrong way, as long as the results are what's desired." Charles Fox

"We have to constantly remind ourselves what we're doing....No Luthier is putting a man on the moon!" Harry Fleishman

"Generosity is always different in the eye of the person who didn't receive anything, but who wanted some." Waddy Thomson

Thanks for the replies everyone. I know it's mostly just experience and learning to get a "feel" for what is right.

I'll post pictures of this build when it's done in a few weeks.

Steve

Please don't sand past 180 on the initial sanding ( raw wood ) as this is not necessary and is even detrimental to the mechanical bond with nitro processes .

I can't agree with that. I can see 180 grit sanding scratches under finish on many woods. 220 is better and sometimes even 320 is required. And a properly applied finish should have no problem bonding with a 220 or 320 grit sanded surface.

180 grit has been an industry standard for prep sanding white wood for finish since I started building cabinets 30 years ago. With their modern high solids coatings most manufacturers are now recommending to white out at 150 to avoid delaminations. The only finish I white out at 220 is for shellac because it has better grip and is thinner material. I prep everything else at 180 and see no sanding marks under my finishes. If you are seeing scratches under your finish at 180 then your technique may need improvement.

Also I am considering doing some hands on French Polish workshops in the future and was wondering what if any interest folks might have in something like that.

_________________
Brian

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

https://www.howardguitarsdelaware.com/

I'm in for French Polish. Please coach me up on that.

Marc

My info/instruction comes from Dale Bartholomew . He is retired from Martin and did run the finishing department there for a number of years . I consider him to be an authority and have seen him work . He knows nitro and finishing in general with it .

I am and am only 20 minutes from you , but you already knew that .

Count me in on a french polish class. I'm only a couple hours away (well worth it).

_________________
- Ben Pak
North Wales, Pa.

Finishing is just as difficult if not more difficult than actually building the guitar. I have put together some online courses on my website for both French polish and spraying lacquer. Perhaps you will find them useful.

Happy Finishing!

http://www.obrienguitars.com/courses/

Finish repair is again more difficult than (re)finishing a guitar too.

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

You will find a lot of different opinions on how fine to sand bare wood. It depends somewhat on the tools you use and the type (and brand) of sandpaper.
Some random orbital sanders manage to leave "swirl" marks even at 180 grit. And some sandpapers are poorly graded and 180 grit will have a few 80 grits thrown in for not so good measure.
I try to use a good quality sandpaper and take things to 180 cami grit. Sometimes I see areas I'm not happy with and hand sand to 220.
Micron papers offer the advantage of having more uniformly sized particles and can give better results, but cost a fair bit more. They may be worth the extra expense when level sanding the finish.
When buying sandpaper note whether it is cami or "P" grit. They use a different grading scale so you need to know how they compare when going from one system to the other.

CAMI and P/ISO grade 180 and 220 are the same thing. Does not apply to the full spectrum, though.