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I was just reading through Cardinals recommended schedule for LuthierLac: http://www.cardinalpaint.com/redBird/newTDS/2079-CLE17937-tds-1.html

1. Seal using Cardinal Vinyl Sealer
2. Scuff with Scotch Brite or 400 grit paper
3. Should use a 6" fan apprx. 9-12" from substrate
4. Apply with an overlapping spray technique two time for one coat
5. Apply apprx .5-1.0 dry mils (5-10 wet mils) each coat
6. 5-7 coats recommended. Allow 7 days to fully cure.

How would one measure the thickness of the coat?

If you spray on acetate or similar, when dry it will flake off & you can measure it. (Usefull in soundholes)

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Dave
Milton, ON

I use a mill gauge card. You spray a pass on something, press in the gauge and read the thickness. By knowing my solids content by volume I can calculate the dry millage. 10 mills is gonna be hard to hang.

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

I use a business card that I attach at the sound hole. While it may not be totally accurate ,it helps me gauge my application. I try and apply 6 to 8 coats and end up with .016 to .020.
I can measure the coverage in about 1 hr of dry time. I know that cure time thickness will be less that the green time I know about what this will be. There are other ways with the different magnetic gauges and such.
It isn't what you put on as much as what you let on

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I picked up a mill card gauge the other day from Sherman Williams and used it for the first time today to see what thickness I'm laying down. I know, I should have used it on the first coat instead of the 6th coat for the first time but oh well - slow learner. What I found out is that I'm laying my coats down at 5 mils wet. I'm using Behlen's instrument lacquer and I'm thinning it 2:1. The results are turning out great! The 5 mils that I'm spraying is at the max of what I would lay down. I'm just on the verge of runs, but I'm not getting any. Laying down 10 mils at 2:1 you would have nothing but runs. Just my observation on what I'm spraying now. Hopefully that helps with your Cardinal lacquer.

Btw - I'm a complete noob at this. Take that into account

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Rob Flindall
Flindall Guitars
http://www.flindallguitars.com
https://www.facebook.com/FlindallGuitars

Behlens sprays fine for me right out of the can though I cut it a bit for the final couple coats. I spray with a HVLP touchup gun with 1mm needle and 25psi at the gun.

Fred

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Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866

learning to finish is such a big part of that final product. I use a thinned mix with up to 20% thinner and retarder. I also went HVLP. I have both a turbine and use compressed air. I am liking the turbine .

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

James, I can't really help you with wet thickness, but if you take a piece of scrap a known thickness, spray a number of coats on it, let it dry for a day or so, and the re-measure you'll know the total thickness of you finish. divide by your number of coats and you'll know your average dry film thickness you put on per coat.
I do this periodically just to make sure things are still as I expect. For example I typically lay down .0007 of dry film thickness per coat. This really helps me.

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Jim Watts
http://jameswattsguitars.com

Hi Fred - unfortunately I don't have nice HVLP spray equipment. I'm using a compressor at 40psi with a better Campbell-Hausfeld gravity fed spray gun. I have no idea as to my needle size. I thinned down to the 2:1 as to something I read in a Stewmac book. After thinning, it lays down considerably nicer than when I started. Proof is in the pudding though I guess. We'll see how it sands and buffs out.

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Rob Flindall
Flindall Guitars
http://www.flindallguitars.com
https://www.facebook.com/FlindallGuitars

Thanks for such practical solutions

Ok, just want to say a few things about wet film thickness versus dry film builds and the addition of thinners to the ready to spray mix. Let's look at the Cardinal stuff mentioned. It has 11% solids by volume as packaged, not a high solids coating by any stretch. So if you are hanging 5 mills wet you are going to net just over half a mill dry per coat. That means at least 9-10 coats to bring the film up to 5 mills before buffing ( my suggested minimum), depending on surface texture you may need another mill for level sanding. Now Cardinal's literature does not mention thinning, the product is basically packaged RTS, small amounts of thinner or retarder may be needed for environmental conditions like high temp/humidity but generally speaking these adjustments will be far less than 10% added to the product. So let's say we reduce a bit due to high temp, 10% even, we have lowered our dry film build slightly. We will now net half a mill less every ten coats so instead of the 5 mills we had previously at 10 coats we now have 4.5 mills, so we will need at least one more coat to get the same film. Now let,s thin out at the 2:1 as mentioned, that's a reduction of 33%. Now we are only applying about .35 mill dry film per coat, so now we need to spray out at least 15 coats to get our dry build. With an average flash between coats of 30 minutes those extra coats with all that thinner mean another 2.5 hrs. in the booth, more exposure ( lots of these chemicals absorb directly through the skin) and the kicker is we have increased our dry time to buff out, it will take more time for the extra solvents to escape. So how long does it take to sand out a guitar? How much longer to sand out a little more texture? Bet it's less than the 2.5 hrs we just mentioned. The extra solvents can also have an effect on things like the pore fill. Every coat you spray actually wets all the product on the instrument all the way down to bare wood, the more solvent or the more aggressive it is the more pronounced the effect ( those who use acetone, take note). This constant re-wetting can cause the oil base pore fill to swell and then shrink causing the pores to reappear on the final finish a few weeks out, it takes time for all that extra solvent to work back out. Even 30 days out without any extra solvents we may be only 95% dry, at a week you may 90% or 85 %, there is no way of knowing but that means that the coating will still shrink. So those who spray and measure rather than measure their wet films will need to think about that, 5 mills at a week may only actually be a little over 4 in the end ( 3 mills is about the bare minimum for a functional lacquer coating). And we haven't even talked about the environmental impact of all the extra solvents.... That's the real reason they are making these products harder and harder to get ( in some cases unobtainable) by non industrial users. Industrial users can still buy anything we want in any quantity as long as our equipment and methods are compliant. Hopefully some of you find this info helpful as this topic comes up fairly regular.

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/