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I have been noticing a very odd problem.

I let the finish cure for about a month or so, and then sand with 2400 and 3600 micro mesh, and buff with medium and fine Menzerna. The problem is even after buffing with medium menzerna the scratch that came from the micromesh, some of them appearing to be somewhat deep won't go away. The buffing wheel polishes up the finish very well but from a certain angle you can see the scratches. I am really tempted to buff harder but from experience it burns the finish when I do that. I have also noticed that the scratches became more apparent when I wipe the finish with naphtha to remove the oil... so the question is, was the menzerna leaving a coating of wax on the finish that made it look as though the guitar was polished, and what can I do to remove those sanding scratches once and for all?

It was less of a problem with polyester repair jobs because I just buff at 1500 rpm (rather than 1000) and press HARD, and all scratches goes away on fine.

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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

The 3600 micromesh is still too coarse; you need to go finer.

Micromesh's rating system causes a lot of confusion, as it's not the same scale as most of us think of(the CAMI scale), and with the P scale thrown-in, it gets even more confusing. But basically, the 3600 MM(micromesh) is only about 1200 grit(CAMI), and with most finishes, you want to go to at least 1500 grit(4000 MM), and with many finishes, 2000 or 2500(CAMI)(6000/8000 MM) is the better ending grit.

Here, print this chart, and hang it in your shop. It may not be the most precise chart, but it's a good start to understanding abrasives.

Also do not sand with the grain when working on a finish.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Try sanding all the way up to 12000 and then use microgloss polish. It is a lot of work, but then no additional buffing is needed.

Very timely, thanks for the chart Mario!

mario
do you use a block ? I like to use a soft cork pad. I find my fingers can make marks

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Are you sure you are transitioning through the grits completely and removing all the scratches left by the previous grit?

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Brian

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

https://www.howardguitarsdelaware.com/

+1

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

My favorite finish sanding blocks lately are erasers. The pink ones are great because they come in different sizes, but this one is my favorite:

http://www.staples.com/Staedtler-Mars-P ... uct_274795

Eventually I transition to a cork block on flat areas, but this works great for the initial pass to quickly.

BTW, that Staedtler-Mars erase with some micromesh wrapped around it is MAGIC on frets! I had to laugh when I saw StewMac's fret erasers.

John, I seem to remember reading advice to sand diagonally with each consecutive grit, different way each time you go up a grade.
I was wondering if this is what you do?
If not, how do you do it, and what grit do you start with?

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

So it would help if I start sanding at 4000 micromesh grit?

I find when I start with a coarser grit like 1500 the sanding scratch was so deep that no matter how diligent I was in going to the next grit, and so on, it feels like the scratch just keeps coming back and wouldn't go away. Also once you sanded up to a point the finish starts sucking on the paper, making it very hard to move. I went with 3600 grit just because I started with that when I was polishing up a Kamaka ukelele (it wasn't polished at the factory) and it worked... the buffing wheel seems to have absolutely no power in rubbing out scratches.

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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

END with 4000 (or higher)


Are you 'wet' sanding? I always wet sand with mm. (except I have some mm for ROS that I use dry)

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Pat

Of course I have been wet sanding, although MM can work dry it clogs rather quickly. I won't use any other brand of sandpaper for finishing after using MM simply because other brands are really rough and stiff compared to MM.

_________________
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

Get sample kits from Eagle: http://www.eagleabrasives.com/buflex.html

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https://soundcloud.com/jeffreylsuits/he ... -runnin-13

Tai, study that chart...

MM "1500" is really 320 grit, and that's what I use to sand the WOOD, before sealing, even....

The 2400 you said you started with is really closer to 800 grit, which is still relatively coarse(rough) if you don't have a deft hand with it.

Since you seem married to the MM, start at 3200, and end at 6000, and all will be golden for you. Sand in opposite directions as you go up through the grits, so that you can tell when you've completely removed the scratches from the previous grit. Do NOT move to the next grit up until you've removed ALL the scratches from the previous one. Always end with sanding with the grain. This way, if any of the finest scratches still remain, they will tend to disappear with the grain lines.

Always use a block; I like the pink erasers, too. Get the big a$$ ones at joke shops(they usually say "for BIG mistakes" on them <bg>) , and cut them into various shapes. I also use smaller white erasers for detail sanding; they're softer, and allow a bit better feel.

When you buff, again, start opposite the final sanding, which means you'll begin buffing perpendicular to the grain(assuming you're going to buff with only two compounds), and again, complete the final buffing with the grain.

Let's all recite, out loud, the guitar finisher's lament:

"We need to find the sumbeech who decided that guitars would have perfectly level and glossy finishes, dig him up, and kill him. Again!"

Amen!!

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"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

I agree with that, but a large majority of customers don't... and the old saying is customers are always right.

I mean a lot of Martins/Taylors are this way, but having worked on some OLD guitars, I much rather have a guitar that sounds good with a rougher finish than a shiny guitar that sounds like poop. FP is so much easier... plus customers who specs FP don't generally care about a really glossy finish because you won't get a plasticy shiny finish with FP.

_________________
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

What's any of that got to do with the sanding scratch issue you're having, Tai?

I was answering the statement above where they said something about people demanding glossy finish on guitars.

_________________
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

[/quote]
FP is so much easier... plus customers who specs FP don't generally care about a really glossy finish because you won't get a plasticy shiny finish with FP.[/quote]

I don't know about that. I'd expect a well done FP finish to be quite glossy. While my FP certainly doesn't look plasticy it does look about as glossy/shiny as I (or I'd expect most anyone else) could want it.

Tai, did you sort out your issue? This post was very timely as I had just ordered some MM pads.
I let my EM6000 cure for 5 days and hit it with the MicroMesh 3200 to 6000 as Mario suggested, (wet-sand with water and a drop of dish-soap) and all is certainly golden.
Definitely my easiest and best hand-rubbed gloss ever - hand-polished with the Meguiars Mirror Glaze 17 then 10 after the MM- no scratches on a dark blue electric build.

Rob

I don't know, it worked well when I polished up a Kamaka uke by ending with 3200 grit. I think I should have ended with a finer grit, I was just foolish in thinking that medium menzerna can polish out scratches.

I have not had any finishing work at the moment so I have not been able to try things out. The lacquer requires at least a month to cure otherwise it gets all soft.

_________________
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

Agreed - I have essentially divorced my buffing setup - Mezerna medium does nothing for me but waste my time....
However, I might try the Lee Valley bars as suggested by Pat H....