Polish for vintage finishes...

[The Kid!]

So I got some Lizard Spit VIP (Vintage Instrument Polish) in the mail today for my '52 J-45 and it says right on the bottle not to use it on cracked finishes. There's finish checking all over this guitar. Do they mean actual cracks (there aren't any cracks) or do they mean finish checking?

I can still return the unopened bottle, but I wanted to take care of the hazing on the area where my arm rubs against the guitar. Just for basic maintenance and protection. I just don't want to do any damage.

[Wade Hampton]

Yes, they mean cracked finishes. I'm glad you read the label before you used it on the guitar.

On a guitar that old and weathered, trying to shine it up is going to be counter-productive. If it needs to be cleaned, use a clean damp all-cotton or microfiber cloth, and clean small areas at a time. If there's some gunk that won't come off with only some judiciously applied moisture and gentle motion, use a (very) small amount of mild soap or detergent (like Ivory Liquid) and carefully clean small areas at a time, immediately followed by a moist cloth with no soap on it to clean up any soap residue.

On any nitrocellulose finished guitar, whenever you shine it up you're doing so by removing a thin top layer of finish. After sixty seven years in existence, that finish isn't thick or robust enough to be polished. Over the years some of it evaporates in a process called "gassing off," where the volatile plasticizer chemicals migrate out of the lacquer, which shrinks it. That's partly why it forms that "windowpane" checking: the lacquer shrinks and pulls away from itself, just as mud on the bottom of a dry stream bed cracks once the moisture in it has evaporated.

Dry Stream Bed



Finish Checking

It's essentially the same process, just with different materials involved.

Short version: don't try to shine the guitar up into something it no longer is. Clean it gently when needed, and leave it at that.

Hope this helps.


Wade Hampton Miller

[00045]

What Wade said

[charles Tauber]

"Checking" and "crazing" are terms that mean "cracked".

The "danger" with using a product such as Lizard Spit on a cracked surface is that the Lizard Spit residue will stay in the cracks after it has been applied and rubbed off. Depending on the product, it often appears as a white residue.

If a damp, not wet, cloth doesn't work to clean your guitar, you could use a cloth dampened with naphtha.

[The Kid!]

Originally Posted by Wade Hampton

Yes, they mean cracked finishes. I'm glad you read the label before you used it on the guitar.

On a guitar that old and weathered, trying to shine it up is going to be counter-productive. If it needs to be cleaned, use a clean damp all-cotton or microfiber cloth, and clean small areas at a time. If there's some gunk that won't come off with only some judiciously applied moisture and gentle motion, use a (very) small amount of mild soap or detergent (like Ivory Liquid) and carefully clean small areas at a time, immediately followed by a moist cloth with no soap on it to clean up any soap residue.

On any nitrocellulose finished guitar, whenever you shine it up you're doing so by removing a thin top layer of finish. After sixty seven years in existence, that finish isn't thick or robust enough to be polished. Over the years some of it evaporates in a process called "gassing off," where the volatile plasticizer chemicals migrate out of the lacquer, which shrinks it. That's partly why it forms that "windowpane" checking: the lacquer shrinks and pulls away from itself, just as mud on the bottom of a dry stream bed cracks once the moisture in it has evaporated.

Dry Stream Bed



Finish Checking

It's essentially the same process, just with different materials involved.

Short version: don't try to shine the guitar up into something it no longer is. Clean it gently when needed, and leave it at that.

Hope this helps.


Wade Hampton Miller

Thank you! I'll use it on the 2016 instead.

[redir]

I really like the Stewmac Preservation polish and find that it leaves nothing behind on crazed finishes. Naptha as mentioned is also a good safe choice that does a great job.

Also just to add one more note, no kind of cleaner should be used on a guitar with an actual wood crack. It might leave behind gunk that makes the repair more difficult.