Measuring finish thickness

[deadedith]

Some of you are able to measure the thickness of your finish. How do you do that?
Thanks
Dave B

[JJDonohue]

When I cut the area for the bridge, I measure the thickness of the finish at the boundary. Some use a frisket tape mask and measure the finish laying on the tape. My polyester thiskness is around 3 mil. My FP thickness is immeasurable...less than 1 mil.

[deadedith]

Ah, so!
Thanks
DaveB

[Tony_in_NYC]

Dave,
Before you get crazy worrying if your finish is too thick, Roger Siminof did some tests regarding finish thickness and its affects on the tone produced on some sample pieces of spruce.
He tested nitrocellulose lacquer, not FP or anything else, so this only applies to nitro lacquer finishes.
He also sprayed the finish on to the test pieces.

I am writing this from memory, but I will check it if anyone wants me to.
The short story is that in his opinion, more coats was better. Short of glopping on a 1/8th inch thick finish, even 20 coats will not hurt tone, and may actually improve it.
I have never met Roger Siminof but I have heard he knows a thing or two about building great sounding instruments. Do with this info what you wish. I for one, have stopped worrying about how thick my finish is. I do 10-12 coats Deft brush on. For one guitar I taped the bridge location, for the other, I scraped it clean after wet sanding. Both had thin enough finishes on them that I was surprised I didn't sand through it. I actually did sand through on #1 but that was on the binding so it doesn't count.
Yet another $0.02 from me. I think I am changing my screen name here to "Tony Two Cents"

[deadedith]

Tony - thanks.
Full disclosure: what I am really after is a way to measure top thickness on a closed box. Short of a pretty fancy magnetic type setup, or a $400 set of calipers, there does not seem to be a way; so I thought hmmmm..some people are measuring finish thickness, I wonder what their method is, could I appropriate it for my purposes?
I did not get that answer; but I did learn about measuring finish thickness which is also something I can use. So thanks for all the input.

DaveB

[tippie53]

When I spray , I use a piece of foam rubber and a deli cup . The foam is under the cup and the cup presses against the top from inside the guitar . This seals the guitar from any debris and overspray. That allows me to place a business card between the cup and the top.
I usually write the thickness of the card on it when I place it into the sound hole. Then as I spray I can mic the card and get a good estimate to the finish build . I agree it isn't the most accurate but it gets me close enough. I look for a .016 to .020 green finish build on nitro.

[Tony_in_NYC]

Tony - thanks.
Full disclosure: what I am really after is a way to measure top thickness on a closed box. Short of a pretty fancy magnetic type setup, or a $400 set of calipers, there does not seem to be a way; so I thought hmmmm..some people are measuring finish thickness, I wonder what their method is, could I appropriate it for my purposes?
I did not get that answer; but I did learn about measuring finish thickness which is also something I can use. So thanks for all the input.

DaveB

WHAT?!?!?
I want my two cents back Dave!!

[deadedith]

Here...,take your d*** money!!
:-)
DaveB

[Ken Hundley]

I like that idea about fillng the soundhole! Never thought of a deli cup and a sponge. Thanks for the idea!

[JAC]

I haven't done this yet, but I have heard of spraying a piece of sheet glass as you spray the guitar (assumes that you spray). So, every time you spray a coat on the guitar, spray a coat on the glass. Easy to see, easy to cut, and easy to measure.