Gibson Mandolin 1913 . Off gassing pick guard .

[Len Biglin]

Hi gang , Ive got an early Gibson mandolin , the pick guard is missing but it must have off gassed in the past and has rusted the frets and caused the ebony board to crumble at the top end . Im just wondering if there is a treatment to remove the acid or whatever corrosive substance is causing this ? Thanks for any input . Len

P.S. Ive got the back off if anyone is curious to have a look ?

[Mark McLean]

Show us please!

Why do you think the pick guard is the cause of the other material deterioration?  I don't know about this kind of chemical phenomenon - but couldn't it be moisture or sweat or something else. 

But please definitely share some pictures. 

[Len Biglin]

Hi Mark , here are some pics . The 4th and 5th show the damage caused by off-gassing of the guard , this is a well known effect , the old celluloid starts to crumble and gives off a gas , this condenses on nearby areas and forms beads of acidic sweat , very corrosive to metal . it is common on arch top guitars where it rusts pickups and frets .The last pic shows a faint number stamped on the block , its not the same as the serial number , so maybe a production number , someone will know ? The back is cracked as it wasn't cut on the quarter , does anybody recognise this back wood ?

[Joshua Levin-Epstein]

That's a nice old mandolin!

Unless I am wrong, the back and sides are birch. The number inside is the Factory Order Number which indicates batches or other internal manufacturing stuff. If you think that is cool, that exact FON is in "Spann's Guide to Gibson 1902-1941. It confirms the year of manufacture. It might even be how the date was determined. As an aside, the serial number is probably written under the label, as well. Please don't think I am any sort of expert. I just read frets.com end to end once every few years. (like painting a bridge).

I am hesitant to ascribe the wood damage to off gassing. It just looks like damage, perhaps congenital to that piece of wood, perhaps made worse by environment and handling. The whole thing looks very dried out. It looks like some attempt has been made to secure the last few frets. Some may disagree, but I would just replace the missing wood at the end of the fingerboard and fix everything else. You might need to add some wood to the back because of shrinking.  

Did I mention that's a nice old mandolin?

[Len Biglin]

Hi Joshua , Well that's very interesting , so what date does Spann's Guide give us ? I think I came up with 1913 but i don't remember how . this poor thing has been sitting in my workshop for 4 years and only got onto my bench when I retired . i am sure the damage is from celluloid , when i got it the small nails were still protruding from the ebony board , but rusted and swollen , I had to cut them off to avoid more damage . Also the brace was loose and back was cracked , i have just removed the back with a hot lamp and spatula as it was the only way to get effective repairs . Sections of lining were also loose . I think I will have to fill the crack with a similar wood which will probably mean sanding and lacquer , bummer ! Thanks for your interest . Len