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suburude
01-16-2014, 10:09 AM
Hi I am new here and want to put a couple of vintage ukes for sale. One the vintage Kelii as crazing I think they call it in the gloss finish ?
I have had a couple of vintage guitars with this crazing if thats what you call it ??? There are no cracks in either of these ukes .
Can you inform me if this is how you would describe this finish thing ?
All help would be appreciated !!! Jim / suburude

mm stan
01-16-2014, 10:31 AM
I think you mean Checking ....Rick turner had a way of fixing them, as he does....

hmgberg
01-16-2014, 11:08 AM
Whatever you call it, it can happen for a variety of reasons. Typically what happens with vintage instruments finished in nitrocellulose is that the plasticizers in the finish lose their effectiveness and the finish becomes brittle and the surface develops small fissures. There isn't a lot you can do to prevent it from occurring, however, if it becomes severe and the finish is failing (no longer adheres to the wood and begins flaking off) you can use an amalgamator to melt into the old finish and secure it. If there is significant finish loss, you may have to level the surface with French polished shellac.

Crazing can happen on new instruments if the instrument is exposed to extreme or rapid changes in temperature or humidity. The finish doesn't flex enough as the wood expands and contracts under these conditions, so it cracks. There is a wide variety of contemporary finishes, so you really have to know what finish is on the instrument in order to determine how to repair it.

suburude
01-16-2014, 11:43 AM
Checking or Crazing ????? :-)

hmgberg
01-16-2014, 11:47 AM
Both terms refer to the same phenomenon.

pakhan
01-16-2014, 12:18 PM
Checking is pretty much as described- a fine network of fine cracks across the surface of the finish. Usually in nitrocellulose finish although it can occur in other finishes (although I haven't seen it in oil varnish or the UV finishes). Hmgberg suggestion of amalgamator can work for nitro finishes although it isn't a guaranteed sucess.

hmgberg
01-16-2014, 02:45 PM
http://www.frets.com/FretsPages/Luthier/Technique/Finish/Lacquer/Amalgamator/amalgamator1.html

Here's a link that may be helpful, or at leadt informative.

I use a Mohawk product in a spray can. I mist it on until I see the fissures "heal." It has always worked for me.

As I said, this is for a lacquer finish. You need to know what finish is on the instrument. You can check it by applying solvent to an inconspicuous spot, for instance around a tuner hole. In other words, you remove the tuner and drop apply a little solvent to the area around the hole that would be covered when you replace the tuner. Start with the least aggressive solvent, like alcohol. Then, lacquer thinner. If the finish softens, the amalgamator should work.