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Tricks for sanding Nitro.
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Author:  James W B [ Sat Oct 18, 2008 9:45 am ]
Post subject:  Tricks for sanding Nitro.
So what is the best and most effecient way to sand Nitro? One thing that really confuses me is how long do I sand with each grit working my way thru the grits? Is there any way to visually or by feeling the wood to know.Maybe sand it pretty much as flat as possible with the coarsest grit maybe 400 or 600 and then proceed with succesive grits? Obviously I`m a bit confused.
James
Author:  Allen McFarlen [ Sat Oct 18, 2008 5:41 pm ]
Post subject:  Re: Tricks for sanding Nitro.
If you're talking about finish sanding in preparation to buffing, i.e.. you're not going to be spraying any more, then this is my procedure.

I start with P400 dry paper and a firm foam rubber block, to level out the surface if there's any orange peel, runs or other large imperfections. P500 if it's pretty good and doesn't need much. The reason you use this coarse of paper is that finer paper only refines the surface, it will not level it. You sand dry because it's much easier to see what still needs more sanding attention. It will still have a gloss on it. If you sand wet, then you're constantly wiping back and drying the surface to check your progress. Be sure to stay away from edges as this coarse of a paper will remove a lot of finish of a sharp edge quick smart.

Once the surface is uniformly sanded, you can then go to wet sanding withP600 through to P1200 or even finer if you like. A couple drops of dishwashing soap helps to lubricate the sandpaper as well.

Lacquer buffs up pretty easy, so you don't have to go much beyond P1200 but if your using something harder like Poly or Acrylic Urethane then the finer the better. This stuff is a lot more work to buff out than lacquer, and the more time you spend sanding more than pays off in time saved buffing.
Author:  JJ Donohue [ Sat Oct 18, 2008 6:34 pm ]
Post subject:  Re: Tricks for sanding Nitro.
All good advice so far but here's something that made a significant improvement in my method. Wait at least 4 weeks after spraying to begin sanding. Yep...4 weeks is much better than 2 weeks. That 2 week extra cure feels drier and makes better powder when sanding.

Better yet, consider what I'm doing now...sending my guitars to Joe White!

Good luck with whatever you decide!
Author:  James W B [ Sat Oct 18, 2008 6:40 pm ]
Post subject:  Re: Tricks for sanding Nitro.
Thanks guys,It took me a while as I was working with it to figure out that I needed to use P400 to start and get it pretty level before going to higher grits.The back has a great shine ,but still a few spots that didn`t quite get leveled.Would it be a problem to re-sand the back and try to re-level.It`s already been buffed to a high gloss,but I`m thinking it might be okay to do this .It seems Mcfaddens is pretty tough stuff .
James
Author:  Allen McFarlen [ Sun Oct 19, 2008 3:03 am ]
Post subject:  Re: Tricks for sanding Nitro.
As long as there is enough material to work with, then there isn't any problem going at it again. Lacquer is pretty forgiving in this regard.
Author:  Rod True [ Sun Oct 19, 2008 7:46 am ]
Post subject:  Re: Tricks for sanding Nitro.
I'll have to disagree with you JJ on the waiting, mind you this disagreement comes with a catch. If one leaves the finish totally along then Yes, I'd agree that waiting 4 weeks is vital, even longer if one can stand it. But...

If you want your lacquer to cure quicker, it's best to do a lite scuff sand with 400-600 the day after spraying your final coats. This cuts the surface tension and allows the lacquer to cure much much faster (like 2 weeks), then you can go through the level sanding and buffing. This is not a leveling but just a quick scuff of the surface (again stay away from the edges).

I also do something similar to Allen and Todd. Dry sand up to 800 which gets everything level, then switch to a wet sanding up to 2000 then it's arm strong to get the sheen I want. I usually like the semi gloss look so it's paste wax and oooo steel wool.

Again the reason to dry sand to get the surface level is as Allen mentioned, you're able to see your progress much easier. You'll know that the surface is level when the entire surface is dull in sheen, meaning there are no shinny spots. The shinny spots are lower levels of finish that have not seen the abrasive touch it.

The other nice thing with lacquer is that you can spray over it even a couple of months later. Again just a lite scuff sand and spray a few more coats if you need to. Let it cure and you can work at leveling it again. So no worries trying to re-level it and going through the finish, you can always spray some more lacquer and it will melt into the previous coats.
Author:  Tim McKnight [ Sun Oct 19, 2008 8:10 am ]
Post subject:  Re: Tricks for sanding Nitro.
The only issue with dry sanding lacquer is that it loads up your sand paper MUCH faster if you use non sterrated papers. If you are going to sand dry then I would suggest using a paper with sterates in it becuase it will reduce loading. These papers are typically lighter in color because of the addition of the white sterates.

To save the amount of final leveling consider shooting three coats a day, witing a few hours between each coat then wait 2 days and block sand between spraying sessions. This will level the surface much faster instead of trying to pour it on and trying to level at the end. After block sanding if you wait a day before your next spraying session it will allow you to take it to the buffer sooner (as Rod mentioned above by breaking the surface tension the off gassing happens quicker).
Author:  James W B [ Sun Oct 19, 2008 8:10 am ]
Post subject:  Re: Tricks for sanding Nitro.
Thanks for all your input guys.Rod that is a great tip about scuff sanding after the final coats.Waiting 4 weeks is what I did this time.Bummer.I`m getting real close to achieving a professional looking finish.I wouldn`t be this close without you folks helping out.
Thanks,
James
Author:  Sylvan [ Sun Oct 19, 2008 8:41 am ]
Post subject:  Re: Tricks for sanding Nitro.
Because lacquer melts into the finish before it, you can safely begin the leveling process with 220 grit dry. The sole purpose of sanding at this stage is to level the finish. It is OK at this stage if you sand through some of the finish to bare wood. Any scratches left will be absorbed by the subsequent lacquer coats. Finishing is not difficult, just demanding in its' preciseness. My complete finishing schedule can be seen at http://www.wellsguitars.com/Articles/Lacquer_Finishing.htm.
Author:  Bill Greene [ Sun Oct 19, 2008 11:08 am ]
Post subject:  Re: Tricks for sanding Nitro.
Tim McKnight wrote:
The only issue with dry sanding lacquer is that it loads up your sand paper MUCH faster if you use non sterrated papers. If you are going to sand dry then I would suggest using a paper with sterates in it becuase it will reduce loading. These papers are typically lighter in color because of the addition of the white sterates.

To save the amount of final leveling consider shooting three coats a day, witing a few hours between each coat then wait 2 days and block sand between spraying sessions. This will level the surface much faster instead of trying to pour it on and trying to level at the end. After block sanding if you wait a day before your next spraying session it will allow you to take it to the buffer sooner (as Rod mentioned above by breaking the surface tension the off gassing happens quicker).


Tim:

Are there any certain non-sterrated papers that you recommend highly? Thanks.

Bill
Author:  npalen [ Sun Oct 19, 2008 11:13 am ]
Post subject:  Re: Tricks for sanding Nitro.
Sylvan
When you make this statement in your article, "Use 400 grit to get the instrument close to level and then switch to 600 or 1000 grit to finish up the process.", are you talking P grade or CAMI grade paper?
Thanks
Nelson
Author:  Sylvan [ Sun Oct 19, 2008 4:43 pm ]
Post subject:  Re: Tricks for sanding Nitro.
Nelson -
I do not know the answer to your question. I use 3M Imperial Cut wet or dry paper for those steps. So, whatever that is I use.
Author:  Arnt Rian [ Sun Oct 19, 2008 6:05 pm ]
Post subject:  Re: Tricks for sanding Nitro.
I prefer to start sanding the final coat with as fine I paper as I can, like 800 grit or so. That means the last coat needs to be very good, or it will be too much work. The reason is that some of those 600, not to mention 400 grit scratches can be very persistent and difficult to get rid of. Like Rod I scruff sand that final coat a day or two after application to speed the cure time, but I still let it sit for close to a month if I can. Those new, soft lacquer finishes ding up real easy during set up... gaah
Author:  npalen [ Sun Oct 19, 2008 6:51 pm ]
Post subject:  Re: Tricks for sanding Nitro.
Arnt wrote:
I prefer to start sanding the final coat with as fine I paper as I can, like 800 grit or so. That means the last coat needs to be very good, or it will be too much work. The reason is that some of those 600, not to mention 400 grit scratches can be very persistent and difficult to get rid of. Like Rod I scruff sand that final coat a day or two after application to speed the cure time, but I still let it sit for close to a month if I can. Those new, soft lacquer finishes ding up real easy during set up... gaah


That's been my experience also. Another caveat is not mixing P and CAMI grades when doing the "progression of grits". I learned this the hard way a few years back that I was chasing my tail when mixing them. Why was I seeing those dang scratches in the beatiful buffed mirror finish?

I now start out with P1500 wet which is equiv to CAMI 800 (approx.) when sanding the final clear coats of nitro. Then use P2000 and P2500 before machine buffing with medium & fine menzerna. Am I going to fine on the grits?

Thanks
Nelson
Author:  TonyFrancis [ Mon Oct 20, 2008 5:15 am ]
Post subject:  Re: Tricks for sanding Nitro.
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Author:  npalen [ Mon Oct 20, 2008 9:55 am ]
Post subject:  Re: Tricks for sanding Nitro.
Tony--Thanks for the info.
Do you find that you have to be fairly agressive with the buffing to get rid of any sanding scratches when using the grits you mention?
How would you rate the grit size of Menzerna medium and fine relative to P grade or CAMI grade sandpaper?
Thanks
Nelson
Author:  Michael Dale Payne [ Mon Oct 20, 2008 10:07 am ]
Post subject:  Re: Tricks for sanding Nitro.
I use to spend a lot of time going through 400p- 2000p then 8000 and 12000 Micromesh before going to the buffer. I have found that if I pay more attention and spend a bit more time during my medium compound and fine buffing sessions that wet sanding through 800p does just as well for me.

I have also found that 2 caps full K1 kerosene in distilled water really reduces the load up and prolongs the paper life during wet sanding.
Author:  Kevin Gallagher [ Mon Oct 20, 2008 8:32 pm ]
Post subject:  Re: Tricks for sanding Nitro.
If you've leveled the initial and middle coats on your way to building the lacquer to the near final thickness, your
final coats should spray very smoothly and should low out to a glass like sheen.

At that point, I would recommend starting with nothing more coarse than 1000 grit and then progressing through
1200, 1500 and finishing up with 2000.

On a full size body with an 16 inch lower bout, each grit should take you no more then 30 minutes to clean up
with the following grit.

This all starts after the first coats were sprayed and allowed to sit for three days or so and then the next set of
coats sprayed after leveling of those coats. These coats are also allowed to sit for three days or so before being
leveled and the following coats sprayed. I like to allow these the same three days or so before leveling them.

A single final wet coat is sprayed and allowed to sit for 30 days before you go to the above grit sequence to get
it ready to go to the buffing wheel.


Buffing is a whole process of its own as well. If you get the lacquer hot during the buff process, it expands, and
as it cools is allowed to shrink more than it should causing the pores to be visible. Check your buffer wheel speed
by holding your hand against it as you would the guitar. You'll quickly get a sense of how it heats up with various
pressures being applied.

Avoid heat and you'll get a perfectly flat and glass like finish. Heat it up and you run the risk of tearing it off or
the appearance of pores in the finish.

Have fun,
Kevin Gallagher/Omega Guitars
Author:  James W B [ Mon Oct 20, 2008 9:44 pm ]
Post subject:  Re: Tricks for sanding Nitro.
I`ve buffed out to a nice glass finish,but there are some scratches as Nelson mentioned.Should I re-buff to try and remove the scratches or re-sand.
James
Author:  TonyFrancis [ Tue Oct 21, 2008 3:17 am ]
Post subject:  Re: Tricks for sanding Nitro.
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Author:  Kevin Gallagher [ Tue Oct 21, 2008 5:31 am ]
Post subject:  Re: Tricks for sanding Nitro.
James,
Resand those areas that still show scratches with your highest or finest grit and go back to the buffer.

I'm with Tony when it comes to buffing technique. A nice light approach allowing the buffing compound
to do the work without heating the surface up.

The compound works its way off of the buff fabric and frequent recharging is essential to keep it cutting
without creating the heat that can cause trouble for you.

A good friend of mine who visits my shop pretty regularly was a third generation polisher for Tiffany &
Company in their trophy shop. He always flips the switch on my buffer when he's here and sinks his hand
into my buffs to feel the heat that is created by their speed.

His comment is always, "Too fast....you need to slow those down a little. Heat is the enemy." He's not dealing
with the same large flat surfaces that we are for the most part or the lacquer over wood as a substrate, but he
does know polishing as he's actually one of the guys who has polished the Vince Lombardi trophies that are
given to the Superbowl winners, the World Series trophy for Major League baseball and trophies for the U.S
Open tennis tournaments and many other well known awards.

Regards,
Kevin Gallagher/Omega Guitars
Author:  James W B [ Tue Oct 21, 2008 5:04 pm ]
Post subject:  Re: Tricks for sanding Nitro.
Thanks Kevin.Should I re-buff with the coarsest compounds again working towards fine ,or just buff with fine.I really appreciate everyone that`s chiped in to help with this post.I feel that finishing is the missing piece to the puzzle for me.
James
Author:  BruceHerrmann [ Thu Oct 23, 2008 5:52 pm ]
Post subject:  Re: Tricks for sanding Nitro.
I have to admit to being a big fan on the Micromesh papers. Recently, I've been taking the finish all the way to 8000 grit. I know it's overkill but it makes the buff-out so much easier.
I have a big wheel on a lathe capable of throwing a guitar 30 feet but rarely use it any more.
I also do body work on cars and so I have a number of buffing polishers. I mount the guitar
securely in a vise and use the foam pads with 3M polish. The finish is the best I've ever been able to get with Nitro. There are a variety of foam pads for car finishes, you may have to experiment with them to find the one you like but it's a very predictable way to get a great polish. Even in tight spots there a pads that work. But with paper up to 8000,some of those
spots are fine after a hand application of polish glaze.
Just my experience. I also shoot with lacquer warmed to about 85 degrees, lays on very nicely and saves some sanding time.
Best
Bruce
Author:  Brad T [ Thu Oct 23, 2008 6:55 pm ]
Post subject:  Re: Tricks for sanding Nitro.
I'm a fan of Micromesh as well. I level with 1500, then use 2400 to get the 1500 scratches out. After that, It's off to the wheel first buffing with medium menernza, then fine.
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