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I took some time to test Royal Lac Post Cat these past several weeks on a “spare” guitar body. To save time, I just did the back and top, but not the sides. Keep in mind, I’ve only finished about 10 guitars so far, so am by no means an expert.

Just a little background…I tried spaying standard Royal Lac in the past. It’s a beautiful finish, but decided against using it regularly, largely due to the long cure time. This new version of Royal Lac doesn’t have that issue. It cures in just 72 hours.

Here are some notes and general observations:
- The finish is beautiful. The depth and clarity is superb. I took photos, but wasn’t able to to capture how nice this finish looks. And it appears to be very hard as well.

- It sprays very nicely. You can safely spray a wet (but not heavy) coat without fear of sags or runs.

- I’m using a Fuji MightyMite 3 with their gravity fed gun and a 1.3 tip.

- This stuff is very sticky and stays that way for a good 10-20 minutes after spraying. I’m used to spraying waterborne finish which dries very quickly. It would be good to have a way to control dust.

- This doesn’t smell as toxic as nitro, but it has a nasty chemical odor until it dries.

- It’s extremely glossy right off the gun. It also clings and shrinks back immediately. As you’re spaying body coats, it will cling to the denser winter grains and exaggerate them (until you level the finish).

- It very clearly reveals any gaps in binding or spruce tear out. I found I could make these invisible by scuff sanding, filling with CA and continuing with my spraying schedule.

- Leveling the finish is more time consuming when compared to Enduro-Var or GF Topcoat. The finish levels fairly nicely with 400 Gold Fre-Cut, but the paper will clog after a bit. I estimate I used a full sheet of 400 for the top and back.

- This finish is not cheap, and there is some waste. I mixed one cup per day and used about 75% of this.

- Max Girouard and Andrew Mowry do four body coats in one day. That’s what I tried and list in the schedule below. But since I’m still building my finishing skills, I think I’ll do 6-8 coats spread over two days in the future. I came dangerously close to sanding through during my testing.

- Clean up is fairly with DNA

- Shrink-back is a consideration. After three weeks, the finish still looks amazing. But on close examination, I can see I don’t have that flat “factory finish” on the top. There is faint shrink back along the grain lines. On the back, if I look very closely at low angles I can see the finest evidence of pores. (I think if I epoxy pore fill as Gore and Gilet describe in their book, this wouldn’t be a problem.) I’m not sure, but I think this type of shrink back is common with French polished guitar as well.

- A big plus for this finish is that it can easily be repaired during the finishing process. I buffed through a small near an edge on the back. Over the course of a few days, I brushed a few coats over this area. Each time, I mixed a very small about of the product and catalyst using a pipette. Once the area cured, I leveled and buffed. There were no witness lines or any evidence of the repair.

I like this finish a lot. It takes a bit more work than Enduro-Var and GF Top Coat, but looks much nicer, is easier to repair (during the finishing process), and may be harder.

I’m waiting to see how much it shrinks back over the few months before deciding whether or not to use it on an upcoming project.


Here is the schedule I followed. This is pretty close to what Max and Andrew recommend. (They have a GAL article in the works.)

- Sanded top and back to 220.

- Pore filled back with Zpoxy. In some areas, I sanded through epoxy to wood. This left me with blotchiness, so I did a final coat of thinned Zpoxy to even out the color. (In the future I’ll do 100% epoxy coverage with no sand through.)

- Sealed with 2 coats of 2 lb de-waxed blonde shellac. 1.5 hour between coats.

- Let dry overnight.

- Scuff sanded the seal coats.

- Mixed 8 oz of Royal Lac Post Cat and sprayed first body coat. Let dry 2 hours.

- Scuff sanded dust nibs with 400 FreCut Gold.

- Sprayed 2nd coat. Let dry 2 hours.

- Scuff sanded again very lightly to get rid of dust nibs.

- Spayed 3rd coat. Let dry 2 hours.

- Sprayed 4th coat. Let dry overnight.

- Level sanded with 400 FreCut Gold. (I took extra care, sanding in one direction instead of back and forth. This reduced heat and paper loading. It was slow going.)

- Mixed up a fresh batch of product, but this time thinned with DNA - 1 oz / pint of product. (This may not be necessary.)

- Sprayed a thin coat. Let dry 1.5 hours.

- Sprayed 2nd thin topcoat. Let dry 2 hours.

- Sprayed final coat. Let cure for 4 full days.

- Level sanded

- Buffed with ColorTone medium and then fine.

Thanks, Mike! I have some of the post cat and am thinking of it for a Uke I'm working on. Appreciate the write up.


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Thanks for taking the time to write this up. I have a question on one step. Did you apply the blonde shellac over the z-poxy as sealer to ensure adhesion of the Royal-lac, or were you concerned that the z-poxy coverage wasn't complete? Or something else?

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Good question, but I'm not exactly sure. Vijay who sells the product recommends a seal coat. He sells a product for this called Seal-Lac, but also has said that de-waxed shellac works ok.

Thanks for taking the time to share your process, Mike. Your impressions are clearly very thoughtful.


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Very nice writeup Mike. It is greatly appreciated.

I have been thinking about giving it a try also. Your info will make it a lot easier.

I don't have any experience with shellac, especially a two part formula. So, my questions are probably laughable, but, does the finish just dry or does it actually cure? (If it cures it will become nearly immune to DNA, if it drys it won't) And after it has cured (?) Would you say it Is it more scratch resistant than nitro?

Any help would be great

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Joe Beaver
Maker of Sawdust

Joe, Royal-Lac is a curing finish. Vijay adds some things to shellac. The science is beyond me, but it's not just straight up shellac. It was actually designed to cure and become nearly impervious to solvents.

James, thank you for that. With what you and Mike have posted here I'm convinced. I'm going to try it on this year's builds. Summer in So Cal is usually a pretty good time to apply finish.

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Joe Beaver
Maker of Sawdust

Mike, thanks very much for sharing your experience and schedule! It is really helpful.

I wrote Vijay recently with some questions about the product. One thing I asked about was using epoxy for pore fill. He recommended against using it unless it is sanded all the way back to wood (see quotes below). I have always heard it was fine to use shellac as a tie coat between epoxy and finish but Vijay’s comment made me think otherwise. Has anyone ever experienced a failure when applying a solvent based finish over epoxy with a shellac tie coat in between?

Interesting Charlie. Mike used a wash coat of zpoxy so it is going to be interesting what will happen long term. I hope he saves the test piece

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Joe Beaver
Maker of Sawdust

That's what I have always done in the past...sand the epoxy to level after pore fill and then apply a wash coat of thinned epoxy to cover sand-through spots. I haven't had any failures...yet.

I'll save the test body for at least three months, but likely longer.

Vijay's comments about epoxy pore filling and sanding back to wood may be a set back for me. My experience so far is that the product has a great deal of shrink back. The finish will reveal even the slightest bit of unfilled pores/grain. With a very high gloss finish like this one, I think it will look bad.

If epoxy is out, what's the next best pore filler that will give us the smoothest surface? CA?

I'd be interested in how Max Girouard and Andrew Mowry pore filled

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Joe Beaver
Maker of Sawdust

FWIW, I attached two photos of the back I finished with Royal-Lac Post Cat. You only see the grain in the close-up photo if you examine it closely.

It's been three weeks since I buffed and shot these images. The finish has shrunk back a bit more and it's slightly more noticeable, but not much.

We would need to double check, but I think they are working with maple mandolins so they don't pore fill.

I would advise anyone wishing to jump on the Royal Lac bandwagon to do some thorough testing and allow several months curing before raising a happy green flag of success. Initially the finish looks awesome but after several months it cracks, crazes and checks. If you want to remove it, there isn't a paint stripper on the planet that will remove it either.

Bottom line ... I lost four guitars which cost me well over $25,000 and months of work.

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tim...
http://www.mcknightguitars.com

Sorry to hear that Tim. Sounds like the worst of nightmares. It makes every problem I've fretted over, or have heard about, not so bad afterall.

Which product did you have the problem with, Royal Lac or the new Royal Lac Pre-Cat?

I'm also wondering what pore fill and sealer you used? That will help guide me on my test panel.

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Joe Beaver
Maker of Sawdust

Sounds like a basis for compensation?

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I also had two guitars craze and it was about two or three months after I had buffed them out. That was with regular Royal Lac and a sprayed finish. I consulted with Vijay several times and it turns out the problem for me was that I sprayed the coats too close together without sufficient time to cure. The guitars will have to be redone. I will sand them back to eliminate the crazed areas then French Polish with Royal Lac. A month or so before I finished the guitars I also sprayed a mandolin. The owner reported a few weeks ago that it is still doing just fine.

Finally, if I recall correctly, Vijay had produced a prototype RL formulation for spraying that was supposed to provide faster building with fewer coats, i.e. higher solids content. Apparently than formulation did not work well and it is not offered.

The bottom line in my mind is to pay attention to Vijay's recommendations and do not try to get the finish on too quickly. Hopefully the post-cat version will be less sensitive to application rate.

And yes, I am continuing to use Royal Lac.

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Steve Smith
"Music is what feelings sound like"

Is it possible to sand it flat again and french polish or something?

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Pat

That's exactly what Vijay told me to do although I have not done it yet. I suspect it will be a bit of a PITA but otherwise no big deal. Fortunately, the two guitars where the finish crazed were prototypes and not for customers. Also fortunately, the one instrument that I did sell that was finished by spraying RL has done fine.

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Steve Smith
"Music is what feelings sound like"

I think Tim's right. We need to take extra caution.

Just to recap - Vijay tells me this new formulation was created with spaying in mind. It was also formulated to be very fast curing. Unlike the normal formulation, it allows for a condensed spraying schedule -- reportedly without the risk of crazing. Andrew Mowry and Max Girouard tested the post-cat formulation on panels and several instruments in 2016. They have had success and their review will be published in American Lutherie. I believe they are now using it on production mandolins.

All that said, I'm not willing to adopt the product until I see how it behaves for several months, at least. So far, I'm impressed with the finish on my test body. One unanswered question is how to eliminate all pores with a product that shrinks-back so much. I don't believe Andrew and Max pore fill their instruments other than their ebony headstock plates.

Pretty sure they're building mostly with Maple, which doesn't need pore filling. You're going to have to pore fill I believe, unless you using maple or some other non-porous wood.

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Jim Watts
http://jameswattsguitars.com

Regarding pore fill, I think Vijay was OK with using epoxy as long as it is sanded back to bare wood and a few coats of shellac are applied before applying the Royal-Lac post cat. I would think that should take care of the shrink back issues.

I'm a big fan of epoxy pore fill but it sounds like a no no with Royal-Lac. (I tried sanding back epoxy to fill grain only then finish with tru oil. It didn't work for me) Royal Lac may be different but I think I will try something else once my trial stock is in. Maybe two coats of seal lac, CA pore fill, another seal lac then the post cat.

Which brings me to a different topic, what brand, method, of CA to use?

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Joe Beaver
Maker of Sawdust