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sanding shellac
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=21942		 Page 1 of 2
Author:  Steve Davis [ Tue Apr 14, 2009 4:16 pm ]
Post subject:  sanding shellac
Does shellac normally clog 220 sandpaper?
Its a fresh mix...but im suspicious
Author:  truckjohn [ Tue Apr 14, 2009 4:17 pm ]
Post subject:  Re: sanding shellac
Dry sanding ..... yes. Dry sanding Shellac seems to clog up sandpaper like mad.
Wet sand with Paint thinner and it works *way* better.

Also... while folks talk about shellac hardening quickly....
and it does skin and seem kinda hard quickly....
I found the stuff seems to take 1-2 months to reach "Full" hardness.
Test it out with your fingernail... if it indents, it isn't fully hard yet.

Good luck

John
Author:  Michael Dale Payne [ Tue Apr 14, 2009 4:25 pm ]
Post subject:  Re: sanding shellac
I am closing my eyes and pluging my ears if we are speaking of sanding a French polish job eek [headinwall] :D :D
Author:  Steve Davis [ Tue Apr 14, 2009 4:39 pm ]
Post subject:  Re: sanding shellac
not quite that bad!
I put a single protective coat onto the top just to keep RW dust etc out and minimise color bleed
Now want to go back and start the real finish as back and sides are sanded but the stuff is clogging..Its first time for me so i was wondering if it wasnt curing properly and maybe I should make a new batch before attempting the fp in earnest
Thanks in advance!
Author:  David Newton [ Tue Apr 14, 2009 4:53 pm ]
Post subject:  Re: sanding shellac
Michael, you and I need to start a purist's club. You can be the first president, and I'll be your "yes" man.
I know that I gave you a hard time earlier, but I'm back on-board the traditional wagon.

A proper French Polish finish should not need any sanding to speak of, though I have been known to lightly knock down some dust nibs with 800 wet or dry before the last one or two sessions. Then again, I'm kind of sloppy in a dusty shop.

Maybe what is being spoken of here is not FP?
I did a camping guitar once with a brushed shellac finish...
Author:  WaddyThomson [ Tue Apr 14, 2009 5:08 pm ]
Post subject:  Re: sanding shellac
I find that my culprits that cause a little wet N dry with oil are the places where the muneca grabs like a velcro strip was under it, and leaves one of those little dark circles of bumps. gaah [headinwall]
Author:  Michael Dale Payne [ Tue Apr 14, 2009 8:52 pm ]
Post subject:  Re: sanding shellac
David Newton wrote:
Michael, you and I need to start a purist's club. You can be the first president, and I'll be your "yes" man.
I know that I gave you a hard time earlier, but I'm back on-board the traditional wagon.

A proper French Polish finish should not need any sanding to speak of, though I have been known to lightly knock down some dust nibs with 800 wet or dry before the last one or two sessions. Then again, I'm kind of sloppy in a dusty shop.

Maybe what is being spoken of here is not FP?
I did a camping guitar once with a brushed shellac finish...


I was actually jesting because it does take some practice and perseverance to learn to build level as you go but once you get the hang of it you never will want to level sand again. Once again the main key to building level is..................... (drum roll please).......................learning to properly spirit-off and to do so after every body session her enduth today's sermon on the virtue of the spirit ;)
Author:  Michael Dale Payne [ Tue Apr 14, 2009 8:57 pm ]
Post subject:  Re: sanding shellac
Steve Davis wrote:
not quite that bad!
I put a single protective coat onto the top just to keep RW dust etc out and minimise color bleed
Now want to go back and start the real finish as back and sides are sanded but the stuff is clogging..Its first time for me so i was wondering if it wasnt curing properly and maybe I should make a new batch before attempting the fp in earnest
Thanks in advance!


that Job should have been done with a 1lb cut as a 2lb cut really is not needed it is a good Idea to give a day to cure out but shellac is a natural resin excreted fro the lac beetle. it will clog paper especially if vigorusly sanded because it heats up causing a gummy mess.
Author:  Martin Turner [ Wed Apr 15, 2009 9:10 am ]
Post subject:  Re: sanding shellac
Steve if the aim is to remove the shellac then attack it with a cabinet scraper first and finish off with sandpaper.

Sandpaper clogs like mad with shellac and if youre not careful you'll get clumbs of shellac forming on the paper which can cause scratching on soft wood like Englemann. I run a cabinet scraper regularly over the sandpaper to clear shellac build up.
Author:  Flori F. [ Wed Apr 15, 2009 9:18 am ]
Post subject:  Re: sanding shellac
For sanding a fp finish, I wait at least 3 days (longer is better) before sanding. Lubricate wet/dry with olive oil. But this sounds like a seal coat? Seems strange that it would clog. If you search the archives, M Payne has posted a way to test your batch of shellac...to check if it's still any good.
Author:  Joe Sabin [ Wed Apr 15, 2009 10:17 am ]
Post subject:  Re: sanding shellac
Here's a secret I'll share for sanding shellac. Get a small piece of short nap carpet, let's say 6" x 12" and have it on your bench. Then sand the shellac a little, then rub the sandpaper onto the carpet like you are trying to sand it, repeat. If you don't let it start to clog, it won't clog, your sandpaper will last through sanding an entire guitar this way.
Author:  Alexandru Marian [ Wed Apr 15, 2009 10:49 am ]
Post subject:  Re: sanding shellac
Flori F. wrote:
But this sounds like a seal coat? Seems strange that it would clog. .


Depends on what sort of seal coat we are talking about. In my case, even after building 5 guitars or so, I am still very bad at dozing the glue, so I always have a bunch of it smeared all over - I must apply very heavy coats (#2 cut, applied with a rag generously, several times) before installing binding for example. Otherwise I'm in trouble, the fish glue I use is difficult to clean and is still able to stick to the wood if the seal coat is too thin.
Author:  Mike Collins [ Wed Apr 15, 2009 1:09 pm ]
Post subject:  Re: sanding shellac
Steve;
one coat of sealer should sand if cured.
I use synthetic steel wool to remove the roughness of the first coat-This is really the grain raised by the alcohol .

Mike
Author:  Steve Davis [ Wed Apr 15, 2009 1:24 pm ]
Post subject:  Re: sanding shellac
Ithink I probably wiped more 2lb cut on there than necessary for a seal coat! Next time i will go 1lb and thin as Michael suggested. Any way all is well Im back to wood and Final sanding.... I promise! Thanks for the great tips
Author:  Michael Dale Payne [ Wed Apr 15, 2009 1:26 pm ]
Post subject:  Re: sanding shellac
The thing about sanding shellac is that it will melt with heat. The friction of the paper can cause enough heat to cause the sanded shellac dust to melt an form small balls of congealed shellac that adhere to the paper, thereby clogging the paper and can cause scratches to the surface being sanded. I am not a proponent of using olive or bay oil during sanding. however wet sanding with 2 cups of water with a teaspoon of dish soap of even better K1 kerosene will work wonders in avoiding heat build up and clogging.
Author:  Gregg C [ Thu Apr 16, 2009 5:53 am ]
Post subject:  Re: sanding shellac
I find I have to use 1200 to sand small globules of shellac that "appear" on the surface !!
Very frustrating considering I am getting a beautiful shine.
I solved my fiber debris problem by using high quality linen from a local fabric store.
but this globule problem still plagues me
I have noticed when ZI use more oil there seems to be less of a problem
Anyone have an idea why I'm getting those globules ??
What am I missing ??

Thanks
Gregg
Author:  Michael Dale Payne [ Thu Apr 16, 2009 9:02 am ]
Post subject:  Re: sanding shellac
Gregg C wrote:
I find I have to use 1200 to sand small globules of shellac that "appear" on the surface !!
Very frustrating considering I am getting a beautiful shine.
I solved my fiber debris problem by using high quality linen from a local fabric store.
but this globule problem still plagues me
I have noticed when ZI use more oil there seems to be less of a problem
Anyone have an idea why I'm getting those globules ??
What am I missing ??

Thanks
Gregg


I pretty much just explained it. When you sand shellac the friction generates heat the shellac dust melts and gels together making theses tinny b-bs of shellac that clog and adhere to the sanding paper. The oil reduces the friction as will water and soap or water and K1 but you need t be using wet dry paper..

Now!!! I must say this!!!Sanding French polish with high grit papers to achieve hi gloss is not the best way to get a high gloss sheen on French polish. If you are sanding with high grit papers to set your sheen you must have by passed the Glazing process. The best and longest lasting sheen on French polish film is glazed in Sanded sheen will not present near the luster possible nor last as long. IMO

The more you glaze the deeper and higher gloss the sheen
Author:  Gregg C [ Thu Apr 16, 2009 9:10 am ]
Post subject:  Re: sanding shellac
Mike,
Thanks for the reply,
The globules I'm getting are not from the small spots of sanding, after I sand these golbules
the spot is wiped smooth and clean. My problem appears while I am bodying and the globules appear in random spots.
Keep in mind these globules are very small and can only be seen right in the reflection. Still they are there and I am puzzled !!

Gregg
Author:  Michael Dale Payne [ Thu Apr 16, 2009 9:20 am ]
Post subject:  Re: sanding shellac
that is a sign of dust or othe rcontamination built up on the face of the muneca. I also suspect you may be wirtking a tad wet. A close up phot would help to tell what is going on..

if you are sitill boding a ma confused whay you would be sanding or even seeing a high sheen starting. you should have a very dull looking film through out the bodding process. Spiriting off will shine it some but very little. The sheen should not start to take place till you start glazing.

Anay little riding and loos glopbs of shellac during bodubg should be melted away each tile you spirit-off. so way confused.
Author:  Gregg C [ Thu Apr 16, 2009 9:31 am ]
Post subject:  Re: sanding shellac
"Any little riding and loose glopbs of shellac during boding should be melted away each tile you spirit-off."
Interesting,
The shine I'm getting is during stiff off, seems to look good.
Anyway,
Maybe I'm not doing the spiriting off correctly,
Spiriting off is to remove the oil, hjowever the pad has oil already on it from the bodying
Should I use a new outter linen when I spirit off ??
If not how does the oil get removed ??

Thanks for the help Mike
Gregg
Author:  Michael Dale Payne [ Thu Apr 16, 2009 9:55 am ]
Post subject:  Re: sanding shellac
Gregg C wrote:
"Any little riding and loose glopbs of shellac during boding should be melted away each tile you spirit-off."
Interesting,
The shine I'm getting is during stiff off, seems to look good.
Anyway,
Maybe I'm not doing the spiriting off correctly,
Spiriting off is to remove the oil, hjowever the pad has oil already on it from the bodying
Should I use a new outter linen when I spirit off ??
If not how does the oil get removed ??

Thanks for the help Mike
Gregg


You should be adding only a drop or two of oil per each load. The oils is used up out of the pad pretty quickly as you body. If your pad is not grimy then no need to change the outer cover to spirit-off. Spiriting-off should be done with a firm but quick passes in one direction per spirit-off session over lapping by about a quarter of the pad width per pass. Glide on one end and glide off the other. Never allow the pad to slow or stop. Do not use back and forth strokes and not in circular motions. Spiriting-off (stiffing) is the process of melting over any high spots with no added shellac, 5-6 drops of alcohol and one drop of oil to prevent sticking as you glide on. The high alcohol load will melt ridging flat. The firm but quick stroke keeps everything level. If there is loose globs on the surface the spiriting-off will wipe them off the end during the pass. When done often (after every body session from the second session on) spiriting-off will build a level surface as you body, leaving no need at all to touch the film with sand paper ever! Now this is not likely to happen for you the first time out the gate but practice will make this possible.

For the life of me outside of dust contamination, I don't understand where the globs are coming from.
Author:  Gregg C [ Thu Apr 16, 2009 10:02 am ]
Post subject:  Re: sanding shellac
Excellent explanition,
Thank You,
don't know where these globs are comming from either, unless I still have too much shellac in the pad ??
I noticed you mentioned adding one drop oil to spirit off, how then do you remove all the oil ??

Gregg
Author:  Michael Dale Payne [ Thu Apr 16, 2009 10:41 am ]
Post subject:  Re: sanding shellac
Gregg C wrote:
Excellent explanition,
Thank You,
don't know where these globs are comming from either, unless I still have too much shellac in the pad ??
I noticed you mentioned adding one drop oil to spirit off, how then do you remove all the oil ??

Gregg



That small amount of oil will not be a problem and will be removed with the next spirit-off. Sounds like you are concerned about entrapped oil. That will not happen if the proper oil is used. The viscosity of the oil will always keep it on top of the shellac. Many people think the propose of spiriting off is to remove the oil. That is only a by product of the process. The real point in the process is to remove the ridging and swirls left in the shellac by the boding process. If you don’t spirit-off after each body session the oil that is on the surface just gets moved around. it does not get entrapped.

I for got to mention that if you spirit-off from upper bout to lower one time do lower to upper the next to aid in building level. If you spirit off always in the same direction you push the melted shellac always in thee same direction and end up with a film deeper at one end.

On the glob issue let me ask this. When you add a new load to you pad each time do you tap the pad after loading on white paper till you see a spoted report or do you go dirrectly to the surface with the new load with out first tapping the pad?. You want to tap the pad till the report on white paper is spotted not a solid spot. if the report (stain) on the white paper is a solid stain then you are too wet. you are wanting to push the new load into the inner pad to start or continue the wicking process. Always remember the new load is only to start the inner pad wiccking shellac. you are not applying the new load to the surface you are wicking the melted shellac from the inner pad through the outer pad and onto the surface.
Author:  Gregg C [ Thu Apr 16, 2009 10:46 am ]
Post subject:  Re: sanding shellac
Mike,
I do blot as you discribed, maybe I'll try blotting a bit more.
Thanks for your time and patience with me today,
I learned a lot, I'm heading home to FP !!
Gregg
Author:  Michael Dale Payne [ Thu Apr 16, 2009 10:58 am ]
Post subject:  Re: sanding shellac
You know you are close enough that a weekend trip to Denver on the 23rd of May is not out of the question for you. have you thought of attending my seminar at Robbie’s classroom (shop) at Redrock Community College?
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