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Question about sealing the top with shellac
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=39121		 Page 1 of 1
Author:  Leftyprs [ Mon Jan 28, 2013 8:09 am ]
Post subject:  Question about sealing the top with shellac
I'm in the process of building my first acoustic guitar as part of the 2013 Newbie Challenge, and I'm wondering if there is any reason not to go ahead with sealing the entire show face of my top with a couple wash coats of shellac rather than just the area around where I'm getting ready to cut the rosette channels & soundhole. I have the top fairly close to final thickness with 120 grit, but could take the show face to 220 with my ROS before sealing it, if that's recommended.

German Spruce

Image
Author:  Andy Birko [ Mon Jan 28, 2013 8:30 am ]
Post subject:  Re: Question about sealing the top with shellac
This kind of ties in to another thread going on about sealing the inside face as well.

If your shop has good humidity control, you shouldn't have a problem. If your humidity has some swing to it, you may have issues with the top curling if/when the humidity swings. It should flatten back out though once the top reaches equilibrium again.
Author:  Michael.N. [ Mon Jan 28, 2013 8:43 am ]
Post subject:  Re: Question about sealing the top with shellac
Go ahead, seal the entire top (not the inside) with Shellac. It won't do a tiny bit of harm but it might stop the Top from picking up dirt.
Author:  Leftyprs [ Mon Jan 28, 2013 8:48 am ]
Post subject:  Re: Question about sealing the top with shellac
Thanks guys. I'm only going to be sealing the outside of the top, and I'm wanting to seal the top now to prevent any dirt etc... from getting into the top while moving on with the build. No problems with humidity here. My shop is ALWAYS between 33%-37%RH, and has been for roughly 2 years now.
Author:  DennisK [ Mon Jan 28, 2013 9:15 am ]
Post subject:  Re: Question about sealing the top with shellac
I'm pretty obsessive about sealing all near-final surfaces (that won't have anything glued to them (except the bridge area which I do seal)). On my first couple guitars, I didn't use any shellac until the end, and they can soak up a lot of sweat/skin oil/dirt throughout the build process. Takes quite a bit of sanding/scraping to get back to a pristine surface.

Plates do curl when the humidity changes, but usually only takes an hour or two to get settled.
Author:  Leftyprs [ Mon Jan 28, 2013 9:22 am ]
Post subject:  Re: Question about sealing the top with shellac
Would you recommend hitting the top with 220 before the sealer coat, or just wait on that until after the box is closed?
Author:  DennisK [ Mon Jan 28, 2013 9:38 am ]
Post subject:  Re: Question about sealing the top with shellac
Couldn't hurt, although 120 is fine enough that the amount of sanding you'll do after steaming out dents at the end will probably be enough to take out the scratches anyway.

I prefer the scraped surface texture, so I just maintain that from start to finish.
Author:  Leftyprs [ Mon Jan 28, 2013 11:46 am ]
Post subject:  Re: Question about sealing the top with shellac
DennisK wrote:
Couldn't hurt, although 120 is fine enough that the amount of sanding you'll do after steaming out dents at the end will probably be enough to take out the scratches anyway.

I prefer the scraped surface texture, so I just maintain that from start to finish.


Thanks. Going the scraper route would certainly help save on sandpaper, and more importantly, greatly reduce sanding time! bliss
Author:  mqbernardo [ Mon Jan 28, 2013 12:53 pm ]
Post subject:  Re: Question about sealing the top with shellac
Your lungs would appreciate it too!
Author:  Leftyprs [ Mon Jan 28, 2013 1:42 pm ]
Post subject:  Re: Question about sealing the top with shellac
mqbernardo wrote:
Your lungs would appreciate it too!


That is no joke! Anytime you can find a way to cut down on wood dust exposure you should try to take advantage of it.
Author:  JoeUlman [ Mon Jan 28, 2013 2:40 pm ]
Post subject:  Re: Question about sealing the top with shellac
Leftyprs wrote:
... My shop is ALWAYS between 33%-37%RH, and has been for roughly 2 years now.
[quote="Leftyprs"]

That’s an extremely narrow range of RH to maintain 24/7, year round. You must have a very sophisticated climate control system in your shop.

Joe
Author:  arie [ Mon Jan 28, 2013 3:10 pm ]
Post subject:  Re: Question about sealing the top with shellac
Leftyprs wrote:
My shop is ALWAYS between 33%-37%RH, and has been for roughly 2 years now.


brutal! how often does your nose bleed?
Author:  AnthonyE [ Mon Jan 28, 2013 4:09 pm ]
Post subject:  Re: Question about sealing the top with shellac
Leftyprs wrote:
Thanks guys. I'm only going to be sealing the outside of the top, and I'm wanting to seal the top now to prevent any dirt etc... from getting into the top while moving on with the build. No problems with humidity here. My shop is ALWAYS between 33%-37%RH, and has been for roughly 2 years now.

I want to know your secret. My humidity is all over the place unfortunately. Maine is not the best place for swings in humidity.
Author:  mqbernardo [ Tue Jan 29, 2013 11:12 am ]
Post subject:  Re: Question about sealing the top with shellac
but you do have fine lobster, that´s got to count for something.

in my workshop i struggle to have it at 47-50% in the autumn-early spring time. i´m envious.
Author:  Leftyprs [ Fri Feb 01, 2013 12:15 am ]
Post subject:  Re: Question about sealing the top with shellac
AnthonyE wrote:
Leftyprs wrote:
Thanks guys. I'm only going to be sealing the outside of the top, and I'm wanting to seal the top now to prevent any dirt etc... from getting into the top while moving on with the build. No problems with humidity here. My shop is ALWAYS between 33%-37%RH, and has been for roughly 2 years now.

I want to know your secret. My humidity is all over the place unfortunately. Maine is not the best place for swings in humidity.


I've not been to Maine, but it can't be much worse than St Louis. The humidity levels here are all over the place throughout the year. My shop is in my unfinished basement, which is all concrete that I've sealed and is roughly 1400sq ft. The basement does have full ductwork that provides heat/AC throughout the year, and keeps a fairly steady temperature of 66F-68F. I use 2 of the 70 pint, 3 speed Soleus dehumidifiers(both on almost constantly) right into my floor drain, and 1 Essick Air 0800 humidifier(when needed), which can put out up to 8 gallons of water a day on its highest setting if need be. The combination works surprisingly well, and I have less than $600 in the 3 machines.

Soleus 70pt dehumidifier

Image

Essick Air 0800 humidifier

Image
Author:  Leftyprs [ Fri Feb 01, 2013 12:23 am ]
Post subject:  Re: Question about sealing the top with shellac
Perfect example of the goofy weather we have here in St Louis...2 days ago it was 75F+ and pouring. Today it was windy with a light blowing snow most of the day, low of 6F tonight with windchills near -10F!!! Top that 48 hour swing for the week! eek
Author:  Bryan Bear [ Fri Feb 01, 2013 2:40 pm ]
Post subject:  Re: Question about sealing the top with shellac
Leftyprs wrote:
Perfect example of the goofy weather we have here in St Louis...2 days ago it was 75F+ and pouring. Today it was windy with a light blowing snow most of the day, low of 6F tonight with windchills near -10F!!! Top that 48 hour swing for the week! eek


The funny thing is these types of changes are totally commonplace for us St. Louisans, but we act surprised every time. People say things like "can you believe we are wearing shorts today and it was 30 degrees yesterday?", and I always say "Yes I can, I've lived here for the last 37 years." We are a strange group. . . Brad, where did you go to high school?
Author:  Leftyprs [ Fri Feb 01, 2013 4:20 pm ]
Post subject:  Re: Question about sealing the top with shellac
Quote:
The funny thing is these types of changes are totally commonplace for us St. Louisans, but we act surprised every time. People say things like "can you believe we are wearing shorts today and it was 30 degrees yesterday?", and I always say "Yes I can, I've lived here for the last 37 years." We are a strange group. . . Brad, where did you go to high school?


Dead on about the ever changing weather and goofy people that live here! Oh, the infamous STL high school question, huh. I went to Parkway West, class of '97. How about you?
Author:  Bryan Bear [ Fri Feb 01, 2013 11:19 pm ]
Post subject:  Re: Question about sealing the top with shellac
Well you know I had to ask. . . Oakville, '93.
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