Overspray?

[Brad Weiss]

The title is the question...

I do notice it's always described as in some way diminishing the value of a vintage piece. I'm sure anything secondary would do that- why is overspray so problematic (and what exactly IS it?)

[JEStanek]

If I understand correctly... it's another coat of finish sprayed on an instrument. #Could be lacquer over varnish... whatever... The poinnt is it makes the finish thicker (i.e., less flexible) and dampens tone/volume.

I'm no expert...

edit: You can replace new tuners with vintage ones... You can't replace an 80 year old finish.

Jamie

[Nuages]

Overspray is the application of the clear part of the finish (usually lacquer) over an existing finish. It is usually done to cover areas of wear that have gone through the finish to the wood. If done properly (light coat) it has little or no effect on the tone of the instrument, relative to its normal finished state. Like any finish, if done improperly it can have a negative effect on tone. Lastly, even if done properly it usually diminishes the value of vintage instruments because collectors of such instruments tend to be obsessive about originality.

[Dale Ludewig]

In the furniture and general woodworking industries, overspray is what happens when you're spraying one area with finish and some "cloud" of finish droplets get onto other surfaces of the piece, causing a pebbly surface that has to be sanded smooth.

[Paul Hostetter]

But overspray, in the instrument world, is what Nuages describes. It's not about tone at all, but rather about aesthetics and authenticity, in that order. In 99% of the cases, it's used as a way of cleaning up battered lacquer finishes, by adding a layer on top. Often the added layer never really bonds with the original (I've manually removed quite a bit of it, and then repaired the original substrate) and looks like it doesn't belong. It can be done well, or badly. Unfortunately it's often the latter. Oddly, when a battered lacquer surface is French polished, people don't seem to complain as much. We judge by results. And as Jamie says, you can't replace an 80 year old finish.

[Eric Pinson]

This a very interesting topic. I am new to the forum so please forgive my basic questions. http://www.mandolincafe.net/iB_html/non-cgi/emoticons/smile.gif

I did not know you could French polish over lacquer. If you french polish an oversprayed instrument with finish checking will the two amalgamate into one and look unchecked?

Thank you,

Eric Pinson

[Paul Hostetter]

French polish is shellac and is compatible with almost any finish. This is why shellac is used as a seal coat under finishes, and why it's also used to seal stains before applying new finishes (extending to covering magic marker graffiti and crayon marks before repainting a wall). It'll cover anything, and anything will go over it.

Lacquer and catalyzed polyester both check, for very different reasons, but neither overspraying or French polishing will do anything about the checking. There are special solvent products for lacquer that can help with checking, but they penetrate the checks and dissolve the finish and make the compromised film flow back together a bit, if all goes well. All French polish will amalgamate is shellac or French polish finish. In certain key respects, French polish is little different than overspray, aside from the fact that it usually looks lots better and has more promise for the future.

[Eric Pinson]

Paul:

Thank you for some great knowledge you pass on to us. I wondered if the alcohol in the french polish would help to make the checked finish flow back together and you answered that question. What are some of the special solvents that would help a checked lacquered finish to merge back to some degree?

Thank you,

Eric

[Paul Hostetter]

I have had reasonable success with slow acrylic lacquer thinner in softening existing lacquer that really helped make some damage go away. I don't consider checking or cold-cracking to be a problem practically or aesthetically, and have never made much of an effort to "fix" it. Nitro lacquer is not very durable or long-lived, though I really like it anyway. I accept its limitations. There is a product called Cellosolve® which is made for the purpose of amalgamating lacquer around checks and cold cracks, and you can visit Frank Ford's Frets.com site right here (http://www.frets.com/FRETSPages/Luthier/Technique/Finish/Lacquer/CheckRepair/checkfill.html) and read all about it. I caution that there is a learning curve involved in using it, or almost anything to do with lacquer for that matter, effectively.