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I finished my first guitar with chemically cured polyester. Since then I've used Cardinal's LuthierLac nitrocellulose. I've never had issues spraying outside, but the guitars come inside to cure for weeks at a time, and recent discussions have had me re-thinking the effect of the off-gassing on my young family's health.

After considering Enduro-Var and oil varnish, I was looking at a guitar I used the original Royal-Lac formula on five or six years ago during my french polishing course, and something just looked alive. So, like all good OLFers, I got on and searched the archives. Royal-Lac Post Cat just seemed to make a lot of sense. It's low VOC, formulated for spray, cures in a week, and has that incredible durability Vijay showed off in his videos years ago.

Even though I'm not quite ready to finish, I wanted to share my plan. I put this together after emailing with Vijay, reading the Giouard-Mowry article from GAL #130, and reading some of the things Don Parker has written here. I shared this with Vijay and got his stamp of approval. All of the comments regarding dry or cure times are directly from him. I'm looking forward to any discussion or comment.

Prep
- Sand surface to 320 grit. Surface should be without scratches or dings and dents.
- Fill with filler of choice (I personally like and already have Z-Poxy).
- Let dry for 2-3x manufacturer's recommendation. Longer when conditions resemble winter.
- Sand back to wood with 320 grit. Wipe thoroughly.

Seal
- Apply several coats of Seal-Lac with a pad or brush. If spraying, thin Seal-Lac 50% and spray 4-6 coats with an hour dry time between each.
- Wait 24 hours and inspect. If more coats are required, follow same schedule.
- Let dry for 7-10 days.
- A decent build up is required since it is going to be level wet sanded later.
- Wet sand with 320 grit and water.
- Wipe throughly and let dry for a couple of days so that any residual water in the system has time to evapora
- If there are sand throughs, now is the time to fix by adding Seal-Lac and level sanding once dry.
- The goal of this step is to get an even foundation for Royal-Lac Post Cat to sit on. It also acts as a barrier coat between the pore filler and Royal-Lac Post Cat.

Spraying
- Mix and catalyst in a 7:1 ratio measured in grams. Only enough for a day's worth of coats. Vijay and Don have both mentioned 21 grams, so that's where I'll start. 21g Post Cat, 3g catalyst.
- Thin apprx 50% with denatured alcohol after mixing
- Spray four coats, approx 3 mil thick, two hours apart.
- Let rest 24 hours.
- Spray 3-4 more coats.
- Let cure 6-12 days.
- You can level after letting the finish rest. Up to you. Do not wet sand before finish is fully cured.[/b]

Level and buff
- Level with 600 grit and water, then 1000 and 1500 to 2000.
- Buff with medium then fine

If padding rather than spraying
- Diluting 50% is a good ratio for padding. It is thin enough for the pad and will get even thinner once equal amounts of finish and denatured alcohol is added to the pad during application.
- Apply coat after coat working with the grain with drying time of 1 hour between coats. You should be able to apply 5-7 coats within a day. Your finish will mostly run out by the end of the day. Do not use any oil for lubrication. If the pad is wet, it will not stick.
- A new pad is required for every session. Do no re-use.

Buffing without a buffer
- Level wet sand starting with 600 grit and going up to 8000 grit or so. Wipe throughly and let dry for a day or two.
- Finish to a high gloss using a automotive swirl remover.

Some of Vijay's Notes
- It's fine to wet sand after the finish is cured.
- The pot life of Royal-Lac Post Cat once mixed with catalyst is 10-12 hours. After this it needs to be discarded. Therefore mix only what you need in a day.
- Royal-Lac Post Cat cures in 72 hours in ideal conditions. Ideals are seldom met. "My rule is to let the finish cure for 2x or sometimes 3x (if it is raining) more than the time recommended by the manufacturer. This applies to any finish."
- 50% dilution is a starting point. You can move up or down based on how your gun works.
- If the dilution rate is high, you may have to resort to a third day of spraying. Each day of spraying is resumed after a rest of 24 hours.
- During spraying if you get holes, it means that finish deposition is too much. Back off on the finish but keep all other settings including rate of gun movement same.

Looks like a good schedule to me. I especially like that you are leveling the seal coat. I sprayed my last one with dilution, not quite 50% and was happy how it went on. I do use a buffer but other than that my schedule is not that different. I level after the first day spraying to see how the first day went. I generally stop at three coats. The finish is hard after it cures so the polishing will take a bit of work.

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http://www.Harvestmoonguitars.com

Thanks, John. Vijay has quite a few of your guitars on his gallery page!

It looks like a great plan, James. I had a very similar schedule in mind after trading e-mails with Vijay. It is good to see that you have confirmed it with him.

I will probably use regular shellac (which I obtained from Vijay) rather than Seal-Lac; Seal-Lac is just a thick cut of dewaxed shellac. And I like to use Everclear rather than denatured alcohol as much as possible, both for making shellac in the first place and diluting finish. Other than those changes, I figure I will be using your schedule. Thanks for putting it all in one place.

I've been wanting to try this post cat version too. The padding technique outline would be very different from what I am doing now. I'm finishing up one now with the regular Royal Lac and I pad it on. With the regular stuff 50% dilution with alcohol would be way too much IMO. I do about 20% and I use walnut oil and French Polish. I've done this with good success on guitars that are over two years old now and still looking good.

From what I understand the Seal Lac stuff is just shellac (Ah I just read Dons post). I wonder if anyone can confirm that. So I'm surprised you would have to wait so long to top coat after that. Part of the draw to the post cat stuff is how quickly it can be done.

JF--

It was a few years ago, but I confirmed with Vijay via e-mail that Seal-Lac is just a thick cut of dewaxed shellac, made with denatured alcohol. I can't remember how thick; I might be able to go look that up at some point.

FWIW (1 sprayed guitar), I went Seal Lac, West Epoxy, then RL direct to the scraped and scuffed epoxy, which was not sanded back to wood. No adhesion issues...

I can’t remember...is the heat/sweat resistance found only in the PC, or the regular RL too?

Definitely! I should say that most of what I posted was copied straight from what Vijay sent me. Any comments about not using oil while padding, cure times, dry times, etc, those are all from the man himself.



I'm going to go grab some Everclear as well. Evidently denatured alcohol is illegal in CA now, which was news to me. We can't buy full strength Everclear locally, but I've dissolved kusmi shellac buttons in what we're able to get, so I'm sure it will do. Vijay sells DA, but it would have been cost prohibitive after shipping since the RL and SL came from LMI.



I believe the original is just as durable! I watched Vijay's original video with alcohol spills, etc. before the Post Cat was a thing.

Thanks...

According to LMI, "Post catalysis helps in creating a cross-linked polymer that is far superior in terms of fast curing, chemical resistance, and hardness. "

https://www.lmii.com/finishes/3094-roya ... quart.html

Whether they mean it's superior to the regular RL product or others on the market is not clear. I like the idea of it being faster though.

I’m happy to say I sprayed my first few coats of Royal Lac Post Cat today, following the schedule I posted above. I’d love to provide some feedback, but honestly I’m not sure what to comment on.

I got the finish in Dec 2020, so it’s just under a year and a half old, hanging out on a shelf in the garage the entire time. Happy to say it's behaving just fine. Shelf life has previously been reported at two years, so this was as I was expecting.

Thinned 50% it goes on like 80% thinned nitro.

The smell lingering around in those first few moments after spraying is sweet. It isn’t bothersome at all. Not something I’d want hanging out in my house immediately after, but it’s garage friendly for sure. Two hours later, no smell whatsoever.

I initially mixed 21g RL, 3g catalyst, 21g denatured alcohol, but this was far to little. I'm not sure that it would have completed a full coat. I ended up mixing an additional 70/10/70. Combined it got me through three coats with very little left over.

I’d be happy to give feedback on anything else?


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I’d like to note that the sweetness is likely from the alcohol. I’m using Vijay’s 200 proof and realized how sweet it smells while I was cleaning the gun later after posting.

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Updates on my first experience using RLPC. Bearing in mind that I haven’t yet buffed it and I’m trying to temper my thoughts…

This is the ideal finish for the person who builds at home and needs the finish to play nice with his or her health, and the health of those around them.

Easy to mix. Thinned 50%, it goes on effortlessly (I got a much nicer surface than my technique deserves). Long pot life (well longer than the 10 hours advertised by my cup test). Most importantly, it’s beautiful. Easiest sanding finish I’ve used. Low to no VOC’s while it hangs in the air immediately after spraying. Absolutely no VOC’s once the finish is dry, at least none that I could smell.

The only two drawbacks are that (1) it’s gotten quite pricey, but I used about 1/4 of the quart spraying 8 coats. And (2), because it’s a thermoset finish, you’re done once it cures. I’d like to touch up a dust spot on my soundboard, but I’ll need to sand it back entirely in order to do so. Once the finish is cured, subsequent coats won’t burn into the existing coats like nitro.


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I’m not trying to be a fan boy or sell anyone on this finish, but I’m also really impressed (delighted) by how easily this finish sands. Working with Festool Granat 500, the majority of this lower bout was level in under four minutes, possibly three. It’s been about two or three months since spraying, so being at full cure certainly helps, but wow…




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My wife gave me 10 minutes before going to the store, so I set a 10 min timer before starting on the back. One minute to spare including a few pauses to clean the paper with my gummy stick. I’m speechless. The surface was decent to start, but I’m not about to tell you I’m a savant when it comes to spray technique.


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I’m curious to hear your final thoughts, I’m looking to do a gloss guitar soon.

I sprayed one once a few years ago and it turned out pretty good. Not perfect, but pretty good…I want to spray back and sides and pad the top. A friend of mine gets his RL topcoat finished at 1.5mil which is admirable…

I've been letting a Royal Lac Post Cat guitar cure for a few weeks, and I'm about to start sanding and buffing. It went on great, just like James reported. I look forward to seeing how it does through this stage.

Did you spray, Don?

Ed--

I did. I'm a relatively inexperienced spray finisher, but it went on fine for me. When I made mistakes, it was because I tried to put too much on at once, and got a few runs. They sanded out easily enough.

Nice. I would like to learn to pad it on. I tried it once, followed the instructions carefully, and it turned into a big sticky mess that I had to spray over with a Preval sprayer. Still turned out ok.

Can't wait to hear your thoughts, Don. I haven't started with my 800 or 1000 yet.



I initially started Tom Bill's FP course using Royal Lac five or six years ago, then switched to "regular" kusmi button lac dissolved in Everclear. The Royal Lac was def a bit tackier.

I ultimately needed to touch up a sand through on the sides and sprayed an additional four coats six days ago before leveling this morning. To my surprise it was still a delight to work with. I expected the sanding to be a bit gummy since I didn’t let as much time pass this time around.

And while I didn’t sand through on the top and it certainly looks very thin, an additional session of 4 coats all around (maybe 2-3 on the top) added to the original schedule might be what I do in the future to be safe.


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Theoretically you only need 72 hours, yeah?

One of these is in my future…

https://www.defelsko.com/resources/dry- ... substrates