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Do fabric in the guitar case react with shellac?   You are logged in as Guest
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alcazaba

 

Posts: 28
Joined: Jun. 30 2013
 

Do fabric in the guitar case react w... 

Hi all, I had a problem with a guitar finished with shellac, that it got marked from the case fabric in the shipment.

Could the fabric of the guitar case react with guitar shellac finish?

The other question is, are old shellac flakes safe to use, in a new mix, or makes a weaker finish?

Thanks
  REPORT THIS POST AS INAPPROPRIATE |  Date Sep. 27 2018 16:09:26
 
Tom Blackshear

 

Posts: 1866
Joined: Apr. 15 2008
 

RE: Do fabric in the guitar case rea... (in reply to alcazaba

First, the case should not be the problem but heat when the guitar was transferred.

Second, old shellac could be rendered out of date for proper use.

It all depends on who built the guitar and what actual finished they used. I know of one builder that used Vaseline for a finish off with shellac, and this made the finish rather soft.
'Another is that the finish could have been new and had not been old enough to polymerize to a solid state.

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Tom Blackshear Guitar maker
  REPORT THIS POST AS INAPPROPRIATE |  Date Sep. 27 2018 17:02:30
 
alcazaba

 

Posts: 28
Joined: Jun. 30 2013
 

RE: Do fabric in the guitar case rea... (in reply to Tom Blackshear

Hi Tom, thanks for replying. I build the guitar myself.

I start the finish two months before shipment but I did a couple of sessions more, about two weeks before shipping it.

The flakes where almost five years old. The mix with alcohol was new. I did another guitar before this one, using same aged shellac flakes, though I used different color. I had no problems, it was shipped during colder weather.

I wonder if different colors of shellac have different toughness properties?

Thanks
  REPORT THIS POST AS INAPPROPRIATE |  Date Sep. 27 2018 18:14:01
 
Echi

 

Posts: 607
Joined: Jan. 11 2013
 

RE: Do fabric in the guitar case rea... (in reply to alcazaba

In my opinion the shellac didn’t cure enough as it was built up too quickly.
My guess is that the guitar seemed ok in your environment but during the shipment she was exposed to a sudden change of temperature/humidity which made it softer. .
Something similar happened to me some years ago when I sent a guitar to Israel.
  REPORT THIS POST AS INAPPROPRIATE |  Date Sep. 27 2018 22:00:18
 
Richard Jernigan

Posts: 2619
Joined: Jan. 20 2004
From: Austin, Texas USA

RE: Do fabric in the guitar case rea... (in reply to alcazaba

I had the rosewood pegs on my '67 Ramirez blanca replaced with machines. The work was done by Kenny Hill's shop in Ben Lomond, California, up in the Santa Cruz mountains south of San Francisco. I was passing through, so the guitar was returned to me within 2 or 3 days.

The guitar was kept in a Mark Leaf case in those days, which captured the headstock with padding on the back and front. A day or two after I got the guitar back I noticed a cloth impression on the front of the headstock, not serious, but visible up close.

The guitar was finished in catalyzed polyurethane at the Ramirez shop when it was built. I don't know what Hill's shop used for touchup after the machine slots were cut. Whatever it was, it apparently was not fully cured when the instrument was put back in the case. The guitar was more than 35 years old at the time, and I don't plan ever to sell it, so I wasn't concerned.

Some time over the last several years, the cloth impression has disappeared. I don't know when, because I didn't pay much attention to it. The polyurethane on the rest of the instrument has thinnned out considerably over the 51-year life of the guitar, presumably due to continued cross-linking of the polymer, maybe due to some continued outgassing of volatile compounds.

At any rate, the cloth impression on the headstock has disappeared altogether: (the ding near the 3rd string roller is due to whacking the guitar against something...)



RNJ

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  REPORT THIS POST AS INAPPROPRIATE |  Date Sep. 27 2018 22:49:16
 
Tom Blackshear

 

Posts: 1866
Joined: Apr. 15 2008
 

RE: Do fabric in the guitar case rea... (in reply to alcazaba

Sir,

Being that you seem to have finished the guitars the same, I would follow Echi with his story about the difference in temperature.

And yes, there can be a difference in drying rates with different resins and colors. But you'll have to contact someone who uses these techniques.

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Tom Blackshear Guitar maker
  REPORT THIS POST AS INAPPROPRIATE |  Date Sep. 28 2018 8:07:53
 
alcazaba

 

Posts: 28
Joined: Jun. 30 2013
 

RE: Do fabric in the guitar case rea... (in reply to alcazaba

Thanks to all for your replies.

I'll buy new shellac flakes and avoid shipping fresh finished guitars. Not fun to have them returned.

Alcazaba
  REPORT THIS POST AS INAPPROPRIATE |  Date Sep. 29 2018 0:16:06
 
Njål Bendixen

 

Posts: 65
Joined: Aug. 25 2016
 

RE: Do fabric in the guitar case rea... (in reply to alcazaba

What is little understood about shellac is that dewaxed shellac is hygroscopic. This means that the flakes will absorb humidity from the air. Wet shellac does not dissolve readily in alcohol. Dewaxed flakes should be used within 6 months. Undewaxed shellac however is not hygroscopic, and has an indefinite shelf live.
  REPORT THIS POST AS INAPPROPRIATE |  Date Oct. 1 2018 20:23:51
 
alcazaba

 

Posts: 28
Joined: Jun. 30 2013
 

RE: Do fabric in the guitar case rea... (in reply to Njål Bendixen

But how do we know the seller didn't have it stored nearly or longer time? Can it be restored by heat, so water leaves shellac?

Anyways, is good information, thanks!
  REPORT THIS POST AS INAPPROPRIATE |  Date Oct. 1 2018 20:53:53
 
Njål Bendixen

 

Posts: 65
Joined: Aug. 25 2016
 

RE: Do fabric in the guitar case rea... (in reply to alcazaba

Only buy shellac from a source you can trust!
  REPORT THIS POST AS INAPPROPRIATE |  Date Oct. 1 2018 21:56:54
 
Tom Blackshear

 

Posts: 1866
Joined: Apr. 15 2008
 

RE: Do fabric in the guitar case rea... (in reply to alcazaba

quote:

Can it be restored by heat, so water leaves shellac?


It's possible that your shop humidity would be low enough to keep shellac for a longer period of time. Mine keeps fairly long at 45%

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Tom Blackshear Guitar maker
  REPORT THIS POST AS INAPPROPRIATE |  Date Oct. 1 2018 22:11:49
 
alcazaba

 

Posts: 28
Joined: Jun. 30 2013
 

RE: Do fabric in the guitar case rea... (in reply to Tom Blackshear

That makes sense. This summer I was on a month and a half long vacation, and had turned off dehumidifier. I live in New England where the humidity reaches close to 100% some times. So it could have absorbed lots of it.
  REPORT THIS POST AS INAPPROPRIATE |  Date Oct. 1 2018 22:19:40
 
alcazaba

 

Posts: 28
Joined: Jun. 30 2013
 

RE: Do fabric in the guitar case rea... (in reply to Njål Bendixen

I bought it at shellac.net, and was good for four years. I had the problem when I finished the orange one and switched to the Super Blonde, or Platina (cant remember exactly which color I bought) Tha's why I was asking if colors made any difference.
  REPORT THIS POST AS INAPPROPRIATE |  Date Oct. 1 2018 22:29:08
 
Njål Bendixen

 

Posts: 65
Joined: Aug. 25 2016
 

RE: Do fabric in the guitar case rea... (in reply to alcazaba

It is not the colour that makes the difference, it is whether it is dewaxed or not. The palest shellacs are always dewaxed, but coloured shellac can be either undewaxed or dewaxed. The test is if it will dissolve completely and quickly in alcohol.

I would not try to heat it to dry it. Just buy fresh, and in small quantities.
  REPORT THIS POST AS INAPPROPRIATE |  Date Oct. 3 2018 9:33:54
 
alcazaba

 

Posts: 28
Joined: Jun. 30 2013
 

RE: Do fabric in the guitar case rea... (in reply to Njål Bendixen

Thanks Njal!
  REPORT THIS POST AS INAPPROPRIATE |  Date Oct. 3 2018 13:30:01
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