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Hi, ive sprayed my kit acoustic guitar body with water based spray, but when scraping away the finish to glue the bridge on, I realised its probably too thick at approx .020 - .025" thick and might dampen the acoustic sound?

Now the bridge is on, its too late to sand it down to thin the finish, but do you think its worth sanding down the back and sides? Thanks.

WOW, that's thick...are you sure about that measurement? Acoustically there would be little benefit to sanding the finish down on the back and sides.

It was my first spray finish! I had some confusing advice that about 10 thin coats would be OK as it would shrink back, but I think they got confused with a nitro finish....probably about 4 would have been OK.

The earlier coats were rough, so each was sanded back quite a lot and I presumed they would be very thin. I had not masked the bridge area, so I realised when I scraped off the finish how thick it was. I realise now I should have sprayed a test piece each time or stuck a business card at the soundhole to measure the finish thickness - next time!

I had read that a thick finish would dampen the sound, so would it need to be a lot thicker than .020 to dampen it? Thanks for the advice.

It's difficult to judge from a picture, but your finish doesn't LOOK excessively thick. How did you measure the thickness? A depth micrometer, or a thickness gage comparing finished and unfinished areas? If the latter, it assumes the wood is the same thickness in both places.

It looks like you have the neck on and the bridge glued on so at this point (from my total beginner/amateur status) I would string that baby up and see how she sounds!

MaineGeezer wrote:It's difficult to judge from a picture, but your finish doesn't LOOK excessively thick. How did you measure the thickness? A depth micrometer, or a thickness gage comparing finished and unfinished areas? If the latter, it assumes the wood is the same thickness in both places.

The finish looks flat, good and clear, if a little undulating on the sides, so doesnt give the appearance of being thick. It wasnt until the last coat that I finally got a good spray finish, so all the previous coats had been rubbed down fairly flat.

It was when I was scraping away the finish (took a long time!) for the bridge footprint that I realised how deep i was having to scrape. I should have measured it then but it was only after I glued the bridge that i actually measured the height of the bridge above the soundboard compared to its known thickness using a packing piece and feeler guages. I will use a business card taped to the soundhole next time!

I think the top finish looks great in the picture. How does it sound?

johnnparchem wrote:I think the top finish looks great in the picture. How does it sound?

I havent got that far yet! Dressing the frets at the moment, making the nut and then I will string her up!

Just curious. Are business cards all a known thickness?