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Nice, not exactly cheap

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Steve Smith
"Music is what feelings sound like"

James--

I had the same issue and had to respray a bit. I sanded through the treble side of the fingerboard and a few spots along the binding of the body. The good news is that the respray went fine. I should be able to get back to sanding next weekend. I am leaving a full 12 days since I sprayed. Maybe I could sand sooner, but I have other things keeping me busy.

The main guitar-building thing keeping me busy is tinkering with UV cured finish materials. I've gotta say, the ability to eliminate cure time helps a lot when you make as many finishing mistakes as I do. If I had been working with UV cured material, those sand-throughs on the Royal Lac would have been a very quick fix; none of this "respray and wait around for almost 2 weeks" stuff.

Regarding that coating thickness gage: That thing costs $2k! I have been known to spend a lot of money on this hobby, particularly over the last 2 years on finishing tools and PPE, but that purchase is too rich for me.

I thought the benefit of the PCRL is that you can sand and buff after 72 hours?

Ed--

If you take a look at the finish schedule that is in the first post in this thread, it is recommended that you let it cure for 6-12 days. You can try to sand sooner, but because there is so much solvent (i.e., alcohol) in the mix that is sprayed, I like waiting the maximum recommended time.

And that's not the only benefit of the post-catalyzed version. It is harder and more durable than the original version. Vijay has confirmed that for me.

It’s a 72 hour cure, but Vijay recommends doubling recommended cure time as a general rule with any finish.

Don, I’m glad to hear it went well! I was worried about witness lines but don’t seem to have any. Note sure if that’s because I didn’t sand through to the old film, or if they just blend that well. I’m looking forward to hearing your thoughts on both matiets once you’ve gotten comfortable with them.

That instrument looks great! Didn’t even realize something like was was in existence. It sure would take away the guessing game when it comes to film thickness.


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Yeah, I think if you plan to do a lot of glossies it’d be a good investment. Want.

I’m really happy with the results after buffing this morning. It buffed as easy as it sands, and I was probably off the buffer in 20-25 minutes start to stop using Menzerna P204 followed by P175 as described by Chris Ensor here about six years ago.

I have such a difficult time organizing my thoughts when it comes to talking about this stuff. Here are just a few bullet points:

- This is 6 coats on top, 10 total on the back and sides, all thinned 50%. My future finish schedule might be 7-8 all around. I didn’t have any sand through on the top or back when I leveled after 6 coats, but did go through in a spot on the sides. That’s when I elected to spray four more coats on the back and sides like I mentioned yesterday. These costs were sprayed a few months after the original sessions and I didn’t have any issues with adherence or witness lines.

- In case I failed to mention earlier, I leveled with Festool Granat 500, followed with Granat 800, then Platin 1000 using my Festool ETS 125.

- Even with the sand through’s and wondering about witness lines, this is really a no drama finish. I think the only downside (aside from future repairability) is cost, but ease of use might make it worth it. There’s easily enough for two guitars in the quart, which I’d guess makes the cost of finish about $60 after adding in hardener and Royal Lac’s alcohol at the time of this posting.

- Looking at the top, I’d say there’s a very very light, very natural ambering—extremely similar to nitro.

- I tried using a mil gauge when setting up the gun to get a sense of how much material I was putting down per coat, and I think they’re each in the area of 3 mils. Each individual coat is two total passes. I’d make a pass over the top, back, sides, then repeat. 45-60 min between coats.
















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Looks good from here! Did you SealLac the spruce? Be very interested to learn the final film thickness when you put the bridge on…

It looks wonderful, James!

Thanks, guys!


I did—but rather than spraying it and using it to build the initial few coats as Vijay recommends, I padded on an even seal coat as you might when using shellac for any method. I probably padded on 3 or so coats in rapid succession as soon as it was dry to the touch until I had even color.


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How are you padding it on without making a sticky mess? I can’t figure out what I’m doing wrong, but I keep getting sticky smears…

Ed—

I can share a tip I learned from Robbie O’Brien, and it has made all the difference for me when I hand apply shellac (which is all Seal Lac is): Thin the mixture to a 1lb. cut. Wipe it on in straight strokes that do not overlap. The fact that the mixture is thin allows it to dry very fast, compared to thicker mixtures. That allows you to re-coat much faster. So, for instance, when wiping on a back, you start on the left, and by the time you make it to the right, the spot where you started is dry enough to re-coat.

In contrast, a thicker cut is not dry when you try to re-coat the same spot. So, it turns into a sticky mess.

I can highly recommend Robbie’s French polishing course on his website. The above tip is part of a way of finishing with shellac that works very well, but is not as traditional as other methods.

Robbie’s fly-on, fly-off method is what I use for Seal Lac and the first part of the RL build. I transition to a technique closer to a traditional French polishing method using a fad with RL, Everclear and walnut oil but still do straight strokes with the grain. The circular thing doesn’t work as well for me with the RL.


Steve

_________________
Steve Smith
"Music is what feelings sound like"

Don, are you diluting in the jar or on the pad like in Vijay’s vid?

Ed--

I cut it in the bottle. That way, I don't have varying results, depending on how much I slopped on the pad. You can always thin it more in the pad, but if you are counting on the thinning to happen in the pad, I worry that it might not be consistently good. That might be an irrational fear.

Don, It’s a little off topic so if we go down a rathole I’ll just message you directly…. Have you experimented with adding acetone to the mix to make it azeotropic? I don’t have a totally solid grasp on the chemistry going on, and I know you’ve read the Gore book. I used this in my uke buildings classes. It dries so fast that even on a small instrument like a uke it’s dry by the time you get to the other side.

What I don’t know is what are the downsides, if any, other than the introduction of acetone to what was a very safe mix of shellac and alcohol.


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Thanks!

I personally used it full strength on a balled up piece of old undershirt, with rapid golf ball sized swirls and very little pressure. I also kept it on the wet side. Not dripping, but not dragging.

Starting in the upper bout and taking my way around again before going back as Don described.

If it was sticky when I went back, I waited until it wasn't. I learned the traditional method of a cheese-cloth cored fad with alcohol and oil in Tom Bill's course, but this was not that.

You may notice my general approach is to be as simple as is possible to be effective. I was just thinking even color and tie-coat here.

Brad--

Great related point. I have been tempted to mix up the azeotropic solution described in the Gore/Gilet book, but since I've been tinkering with the UV cure stuff, I haven't had time yet. I'm glad to hear it worked out in real life during your uke building classes! That's encouraging. I doubt there are any downsides that we don't know about. Acetone smells, and you shouldn't breath a lot of it, but we know that. Keep exposure to the chemical at a minimum and all should be fine.

I do know that, next time I French polish an instrument, I will go this route. I'm now all about the minimization of person hours when it comes to finishing. I French polished my first seven instruments, and hand brushed #8, so I've paid my dues when it comes to laboring forever over the finish. I also don't have the best experience with the use of lubricating oil when I French polish. I just seem incapable of removing it once I'm done. That probably means I used too much.

Alright guys, drumroll please…

Film thickness on the top is .005” at the fretboard extension.


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Good info!

.003-.004 at the bridge. I’m gluing on the bridge and thought to measure a few spots first. Makes sense since I put a few extra passes of the sander in on the lower bout when leveling.


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Nice! I’m brushing one right now, curious as to what I’ll wind up with. A film thickness meter would be a game changer right now, lol…

James, are you reporting that the respray of the sand throughs burned into previous coats without witness lines? Uhh…asking for a friend, lol.

And if so, how did you prepare the offending areas for respray?