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Finish Sanding
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=44044		 Page 1 of 1
Author:  fingerstyle1978 [ Tue Aug 26, 2014 10:09 pm ]
Post subject:  Finish Sanding
What is a realistic amount that you can expect for a finish to fill in low spots? Right now I am using Shellack (don't remember the cut), there are a few low spots that I can't really sand back to without thinning the hell out of the binding. I've already routed off the worst spots and fixed them but there are some a few left that are kind of bothering me. However, I am out of Macassar ebony that I used to bind it and I'm not buying any more.

When you finish sand and the sides have low spots should you sand them down and disregard the binding thickness or try to fill it with something?

Lesson learned- finish sand before binding.
Author:  johnparchem [ Tue Aug 26, 2014 10:59 pm ]
Post subject:  Re: Finish Sanding
I have had to learn that lesson as well. a couple of times. The last time, I used one of Al Carruth scrapers from stew mac. It has a curved profile (look at the web site to understand). I scraped the sides with the curve of the scraper going away from the binding. It allowed me to get the sides level with out thinning the top of the binding. Sure there it is a very gentle curve on the binding, but I have never had anyone notice it. It was just enough to level the sides without thinning the bindings as seen from the top or back.
Author:  meddlingfool [ Tue Aug 26, 2014 11:02 pm ]
Post subject:  Re: Finish Sanding
Do you mean dimples from ripples in the sides? Shellac will take an awful long time to layer up I'm afraid.

I do a relief cut when I route the excess off the top and back plates. Basically anything less than the height of the binding, and less than it's thickness, so that you don't have to sand end grain. Then I add witness lines on the sides, and sand the sides with 100 grit and a flat hard block that extends past the sides and sand til the sides are smooth and flat.

Then I route the binding channels. Then I repeat the process to level the bindings.

If you follow this protocol, you can get bindings that have very very little variance . The added benefit is that the bulk of the work is already done, so it takes a lot less elbow grease to level the bindings...
Author:  fingerstyle1978 [ Tue Aug 26, 2014 11:53 pm ]
Post subject:  Re: Finish Sanding
meddlingfool wrote:
Do you mean dimples from ripples in the sides? Shellac will take an awful long time to layer up I'm afraid.

I do a relief cut when I route the excess off the top and back plates. Basically anything less than the height of the binding, and less than it's thickness, so that you don't have to sand end grain. Then I add witness lines on the sides, and sand the sides with 100 grit and a flat hard block that extends past the sides and sand til the sides are smooth and flat.

Then I route the binding channels. Then I repeat the process to level the bindings.

If you follow this protocol, you can get bindings that have very very little variance . The added benefit is that the bulk of the work is already done, so it takes a lot less elbow grease to level the bindings...


More like a circular low spot about 1.5-2" in diameter. I've just been trying to fill it by brushing shellack and then sanding back. It's better but not good. Just wondering if it's worth the effort to try to fix or just accept it as another mistake.
Author:  meddlingfool [ Wed Aug 27, 2014 12:20 am ]
Post subject:  Re: Finish Sanding
Pics?

It sounds like a low spot from side bending. Next time you bend, hold a straightedge over it and you'll see waves in almost every wood.

If you want to use shellac, just pile on layer after layer without sanding back, until you can lay a straight edge across without seeing a gap...shellac will take a lot lot lot of layers to build up...
Author:  DennisK [ Wed Aug 27, 2014 12:35 am ]
Post subject:  Re: Finish Sanding
fingerstyle1978 wrote:
More like a circular low spot about 1.5-2" in diameter. I've just been trying to fill it by brushing shellack and then sanding back. It's better but not good. Just wondering if it's worth the effort to try to fix or just accept it as another mistake.

Trying to fill by layering dissolved shellac takes forever, especially accounting for the week or more that it takes to fully dry and shrink before leveling. But you can melt flakes with a hot knife to do quick filling, that's safe to level right away. Might be your best bet at this point, depending on what style of finish you're going for, and considering that it's on a dark wood where the color of the thicker shellac layer won't show too much.

The other solution I might use is to take a card scraper, and flex it a bit to scrape the full width of the side slightly concave, so there's no obvious divot. But with ultra-gloss on black, the specular reflections are what you'll see the most clearly, and they'll highlight any surface curvature like that. For a less glossy finish, then it would be ok.

And yes, the proper solution is to level the sides before cutting the binding channels. I use a scraper. Faster and less dusty than sanding, and no need for multiple grits :)
Author:  meddlingfool [ Wed Aug 27, 2014 1:32 am ]
Post subject:  Re: Finish Sanding
I can never get the scraper sharp enough....
Author:  Michael.N. [ Wed Aug 27, 2014 5:35 am ]
Post subject:  Re: Finish Sanding
The worst are the sudden dips. Gentle concavity or convexity are fine in my book, I don't spend time trying to eliminate that type. In fact I prefer it. I'm afraid I really hate that ruler straight, glossy look that you sometimes see on Sides. It has a plastic wood look about it. then again maybe it's just my odd visual taste.
Author:  B. Howard [ Wed Aug 27, 2014 8:00 am ]
Post subject:  Re: Finish Sanding
Finish fills nothing. Lacquer, shellac, poly....it doesn't matter. If you do get it thick enough to fill a defect it will usually crack or craze in a year or so. There are options to fill under the finish with clear material. Epoxy, System 3 SB112 is optically clear and will be virtually undetectable. Z-poxy is not! A clear burn in fill is usually my first choice for filling in defects due to the time factor, it is very quick. It too will be all but undetectable but large areas would be a real pain. There are other methods but these two are easy to do and done with materials readilly available to most everyone. No matter how you fill it there will be some "lensing" or optical distortion caused by the extra thickness of material. it acts just like a lens.
Author:  jfmckenna [ Wed Aug 27, 2014 8:19 am ]
Post subject:  Re: Finish Sanding
I agree with Howard on this one, the finish is not going to fill anything except maybe pores and even then it takes forever. I've used epoxy to fill worm holes and it works just fine. I use it to fill knot holes in furnature too and it renders as a clear spot. OF course you can tell it's there but without looking too close you don't notice it.
Author:  Clay S. [ Wed Aug 27, 2014 12:35 pm ]
Post subject:  Re: Finish Sanding
Perfect is the enemy of good. If you only accept flawless work you will never "finish" anything. The next one will be better, so just be happy with this one being "good enough".
Filling the low place with epoxy and then doing an epoxy fill on the rest of it may give you a flatter side, but you would want to strip off the shellac first. As Brian said, finish fills nothing.
Author:  Greg B [ Wed Aug 27, 2014 2:03 pm ]
Post subject:  Re: Finish Sanding
Yeah, finish will not cover up anything. A final finish can only be as good as the prepared woodwork underneath.

That said, clear burn in stick can be pretty much invisible, especially under lacquer or shellac. It will only work for small divots and things like that though, and keep in mind whatever is underneath it will be seen. It won't fill in low spots or ripples or anything like that.

If you're totally not happy, just redo the binding, or else live with it. There's no such thing as perfect anyway.
Author:  fingerstyle1978 [ Wed Aug 27, 2014 9:56 pm ]
Post subject:  Re: Finish Sanding
I haven't touched it since this latest coat. I'm not sure what do do so I'm at a standstill. With the 4-day weekend I'm thinking I'll just let the mistakes go. There are plenty anyway and I need a player.

ImageImageImage
Author:  fingerstyle1978 [ Wed Aug 27, 2014 10:21 pm ]
Post subject:  Re: Finish Sanding
Clay S. wrote:
Perfect is the enemy of good. If you only accept flawless work you will never "finish" anything. The next one will be better, so just be happy with this one being "good enough".
Filling the low place with epoxy and then doing an epoxy fill on the rest of it may give you a flatter side, but you would want to strip off the shellac first. As Brian said, finish fills nothing.


You are probably right. This is my third first build. The first one I was so disgusted with that I couldn't even look at anymore and gave it away to a friend that was asking about it for his kid.

The second one shattered on the floor after a drop during finishing.

So screw it I'm just going to finish this one and live with the small imperfections.
Author:  Lonnie J Barber [ Thu Aug 28, 2014 9:23 am ]
Post subject:  Re: Finish Sanding
Looks good from here. Keep on keeping on. You should see my last binding job. A total comedy of errors. Well,maybe not that bad. But you know what I mean. We start out it's perfect in our minds. Then we start slicing and dicing. Yuck. I like your guitar by the way. Just hold your finger over that spot when you show it to someone. They'll never know.


Sent from my iPhone using Tapatalk
Author:  SteveSmith [ Thu Aug 28, 2014 3:25 pm ]
Post subject:  Re: Finish Sanding
Finish it and move on. Make more [:Y:]
Author:  DannyV [ Thu Aug 28, 2014 3:44 pm ]
Post subject:  Re: Finish Sanding
fingerstyle1978 wrote:

So screw it I'm just going to finish this one and live with the small imperfections.


Good plan. And don't worry. You'll find plenty of and and way more creative ways to screw up in the future. Most of us have. Might not be perfect to you but it's still a cool looking guitar.
Author:  meddlingfool [ Thu Aug 28, 2014 4:38 pm ]
Post subject:  Re: Finish Sanding
That's the best approach. Now you know what to next time (recess top and back plate and level sand before binding) so it won't happen again.
Author:  jfmckenna [ Thu Aug 28, 2014 4:57 pm ]
Post subject:  Re: Finish Sanding
fingerstyle1978 wrote:
Clay S. wrote:
Perfect is the enemy of good. If you only accept flawless work you will never "finish" anything. The next one will be better, so just be happy with this one being "good enough".
Filling the low place with epoxy and then doing an epoxy fill on the rest of it may give you a flatter side, but you would want to strip off the shellac first. As Brian said, finish fills nothing.


You are probably right. This is my third first build. The first one I was so disgusted with that I couldn't even look at anymore and gave it away to a friend that was asking about it for his kid.

The second one shattered on the floor after a drop during finishing.

So screw it I'm just going to finish this one and live with the small imperfections.

He is most definitely right. Get it done and move on. Honestly almost anyone you show that you have built this guitar is going to be in such awe that you built a guitar in the first place that they won't even notice the most major of cosmetic flaws. Everything as far as I can tell looks great from here so if it sounds and plays good you have a winner.
Author:  unkabob [ Fri Aug 29, 2014 1:57 pm ]
Post subject:  Re: Finish Sanding
Satin finish can hide a lot of minor blemishes.
The guitar looks good.

Bob :ugeek:
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