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PostPosted: Sun Jan 06, 2013 8:45 pm 
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Cocobolo
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Unfortunately, I don't have any high-tech way of telling when my finish coat has built up to a sufficient thickness. So I'm sort of going by intuition, and using some visual cues to decide when enough is enough.

The guitar that I'm currently spraying has 4 coats of seal coat, and 8 coats of top coat. From my visual cues - i.e. how it's rounding over a bit, and softening the edges on the masking tape - it looks to me like my work here is kinda done.

Does anyone here have any other 'low-tech' tricks of the trade to share in terms of determining when to stop spraying?

Thanks in advance...


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PostPosted: Sun Jan 06, 2013 9:26 pm 
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Ken, I shoot EM6000 with wets coats about 2 mil thick. Say 30% of that are solids that will remain as the coat dries, leaving a film thickness of less than a mil for each coat sprayed. I shoot about 10 coats on the top, so that would give me a total film thickness of 0.006" (.002*.3*10) before taking into account the finish removed from leveling and buffing.

Maybe this will help. If you don't have a wet film gauge, it may be worth picking up one. They are dirt cheap.

Ken

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PostPosted: Sun Jan 06, 2013 9:44 pm 
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Koa
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Not sure what seal coats you're using, but I use shellac followed by typically 18-20 coats of EM6000. Did the same with Ultima. This will leave in the order of 5 mils dry, before leveling & buffing. (You might get there sooner, but that's what I do.) Deposition is important (to prevent runs, coats should look only briefly wet). The low tech way I learn deposition is a piece of plastic (acetate, coffee can lid etc) immediately inside the sound hole...... when nearing the end, break off a chip & measure thickness.

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PostPosted: Sun Jan 06, 2013 9:55 pm 
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I use a piece of cardboard with foam underneath to plug the soundhole, on the piece of cardboard I tape a small piece of wood which I write the thickness on and just measure the finish as I go...I have used Em 6000 on several guitars and my finish schedule seem to always change wow7-eyes On my last one which was the best finish I pore filled with z poxy, shot 2 coats of Em 1000 then about 8 coats and leveled sanded then about 8 more coats, a good level sanding makes a big difference in the final finish...I think I am going to try the Polywhey everyone has been talking about on one I am finishing up now , seems with Em 6000 I always use between 15 and 20 coats, I am sure it depends on your spray equipment and technique , I also use a small gun with a .8 mm tip, I think, but I get good results with less overspray....

I love the stuff pizza

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PostPosted: Sun Jan 06, 2013 11:00 pm 
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Cocobolo
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Thanks for all of the replies, guys! It's really useful info.

So it looks like 15-20 total coats is the concensus. I might be able to stop right now, at 16 thick coats of finish, or I could drop fill a couple of tiny spots, level sand, and shoot a few more. Decisions, decisions.

Dave, my full schedule is several coats of Z-Poxy (I like 4-5 thin coats as opposed to 2 thick ones); several coats of shellac (some may think I'm crazy, but I do 6-8 coats, leveling a couple of times); 4 coats of EM6000 seal coat (it seems to have more solids in it, and builds faster than top coat) - thorough leveling afterwards; and now I'm at 10 coats of EM6000 top coat.

I think I shoot thicker than most folks, and maybe a little thicker than I should - I get that blueish look on a lot of coats, then it fades away as each coat dries / gasses off. I'm right at the edge of running, often. I shoot in 45-minute intervals, scuffing before each new coat with micro-mesh, to remove any dust or fuzzies, then tack, and re-shoot. I did a thorough levelling after the seal coat, so my finish is pretty flat right now.

Ken, I've never heard of a 'wet film gauge' - I'll be looking into that.

Thanks again for all the input. I'll put it into the cerebral file cabinet!

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PostPosted: Sun Jan 06, 2013 11:44 pm 
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First name: Kenneth
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Dave has had success with 20 coats on the top and apparently he is shooting thinner coats than me or leveling more throughout the process given his final finish thickness, but if you are laying down a thick coat, 20 coats is a lot of finish on a top! I try to keep my final finish thickness on the top to 3 mil. If I do a burst, it may get up to just over 4 mils. Even on my necks, backs, and sides I limit the number of coats to 15 to 16.

Do you want to hide all the grain texture or do you just want a finish thick enough to protect the guitar? Only you can answer that. After you have leveled and buffed the top, remove the mask and measure your finish either on the mask or on the guitar. You will then better know how to approach your future guitars.

Ken


Ken Mitchell wrote:
Thanks for all of the replies, guys! It's really useful info.

So it looks like 15-20 total coats is the concensus. I might be able to stop right now, at 16 thick coats of finish, or I could drop fill a couple of tiny spots, level sand, and shoot a few more. Decisions, decisions.

Dave, my full schedule is several coats of Z-Poxy (I like 4-5 thin coats as opposed to 2 thick ones); several coats of shellac (some may think I'm crazy, but I do 6-8 coats, leveling a couple of times); 4 coats of EM6000 seal coat (it seems to have more solids in it, and builds faster than top coat) - thorough leveling afterwards; and now I'm at 10 coats of EM6000 top coat.

I think I shoot thicker than most folks, and maybe a little thicker than I should - I get that blueish look on a lot of coats, then it fades away as each coat dries / gasses off. I'm right at the edge of running, often. I shoot in 45-minute intervals, scuffing before each new coat with micro-mesh, to remove any dust or fuzzies, then tack, and re-shoot. I did a thorough levelling after the seal coat, so my finish is pretty flat right now.

Ken, I've never heard of a 'wet film gauge' - I'll be looking into that.

Thanks again for all the input. I'll put it into the cerebral file cabinet!

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PostPosted: Mon Jan 07, 2013 12:49 am 
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Brazilian Rosewood
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I wish I were not so tired... I'd do the math for you. But an end result of 6-7 mil takes about 21 coats. It's hard to say for sure since I level sand every 7-8 coats. Each time with higher grits. So I'm guessing I end up with 25 coats or so if all goes well. A few more if I hit some snags. Search this forum and you will find the average film thickness (for one spray)

Mike (or is it 6-7 hundredths?)


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PostPosted: Mon Jan 07, 2013 12:51 am 
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The real key with EM6000 is to let it rest for a few weeks after your last coat before working to a final finish... Not as demanding as nitro in this respect, but two weeks of cure makes a world of difference


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PostPosted: Mon Jan 07, 2013 10:10 am 
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It all depends on how thick your coats are sprayed so both 10 coats or 20 can still be "correct". Obviously, the thinner the final thickness the better. I am with Ken, I usually shoot 10 coats with 3 light levelling sessions and the coats appear to be a very wet film when sprayed. The longer you wait to final level and buff the better, it will shrink back. Also, let it sit for a day or two after buffing before touching it at all, it seems to soften it and it takes a bit to get back to its normal surface hardness.

The finish is soft but decent enough looking and very easy to apply. It also repairs perfectly, which I love. I have seen people's sweat react and bubble the finish so I will not use it on a neck.

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PostPosted: Mon Jan 07, 2013 10:50 am 
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There is now a lot of experience here with EM6000. One thing I have long suspected is that if you apply the coats too thick, there is a risk of creating more blue haze. I do not know why that would be the case. But as a result, I shoot for more light coats as opposed to heavy coats. It's probably sheer superstition on my part. I will say I now spray necks and bodies separate so I do not build up a fillet at the neck joint for this very reason. I will also say I agree that the thinner you can make the final film, the better. Especially on dark woods. On my current two guitars, I am spending an inordinate amount of time and effort making sure the epoxy fill is perfect before I spray EM6000 so I can go as light as possible.

Mike


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PostPosted: Wed Jan 09, 2013 11:24 pm 
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Cocobolo
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Well, I stopped spraying last night at 18 coats on the top, and 22 coats on the back, sides, and neck assembly. With the 4 seal coats, that equals 22 for the top, 26 for the rest.

I measured as best as I could on some of the masking tape that came off, and it looks like I ended up with between 6-7 mil on the top. This seems to fall within the recommended range that people are shooting for, so I'm pleased.

Thanks again for all of the input - it's always helpful and valuable!

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PostPosted: Wed Jan 09, 2013 11:43 pm 
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Brazilian Rosewood
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Ken, that sounds similar to my experience. Make sure to let it cure before final sanding and buff. And post final pics!

Mike


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PostPosted: Thu Jan 10, 2013 9:18 pm 
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Cocobolo
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Will do, Mike! Give me about 3 weeks ;)

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