Official Luthiers Forum!

In doing some finish planning for a guitar I have almost completed, I pondered this question: Is Royal Lac Post-Cat more durable than the original formula, or does it only provide the advantage of a faster cure time? I don't remember this being addressed here on the OLF, so I asked Vijay Velji, who makes the stuff. Here is his response:

"By the nature of Chemistry, Post Cat finishes are always more durable in terms of solvents and scratch resistivity. The added advantage is that it cures faster due to the catalyst that forces film forming as a faster rate."

I think this is a pretty definitive answer to the question, and hope it is helpful.

Thanks for that. This confirms what we have all suspected. it doesn't tell us to what degree the difference is though. I remember his site having some durability test results comparing shellac to some other finishes. I don't think post-cat royal lac was around yet though. I wonder if that was updated?

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

It has not been updated, Bryan. But since the original formula scored well, and Vijay is saying the Post-Cat is even tougher stuff, I’m encouraged. There’s an electric guitar builder who has posted a handful of videos on YouTube, touting the durability of Royal Lac Post-Cat. I find that to be pretty useful, too. If an electric builder thinks it is a durable finish, that says something.

Curious is this stuff repairable like shellac? Excuse me I have 0 royal lac experience.

No, after full cure, it’s not repairable in the same way as shellac. It is a thermoset finish. Shellac is a thermoplastic finish. But there are other repair techniques, the kind that sorta work on the other modern finishes.

No free lunch, right? There’s a downside to everything.

So is this some sort of additive to the regular Royal Lac stuff or is the post cat all mixed up in a can?

Can you pad it on like FP?

Brush it?

Or can you only spray it?

JF--

The Post-Cat version of Royal Lac is not pre-mixed. In fact, calling any finish post-catalyzed signifies that you add in the catalyst right before you want to use the finish. Pre-Cat is what you would call finish with the catalyst already mixed in.

I don't know all of the chemistry, but according to Vijay, it is inherent in any post-catalyzed version of a finish that it is going to be tougher. I'll take his word for it.

You can pad on Post-Cat, but you can't use oil, and you can't really do the whole swirly in circles thing we do with French polish. The Post-Cat doesn't dry fast enough to get away with that. But you pad it on in straight strokes, wait for it to dry, then repeat. It sounds like brushing can work, too. Vijay has videos on YouTube regarding how to apply it by brush and by pad.

It is nice to spray, I get no orange peel it levels nicely, it does not drip. I just finished spraying a ukulele. I heard people that have had success padding it on. I believe some dilute it with alcohol after mixing. I have only sprayed it.

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http://www.Harvestmoonguitars.com

Here are padding instructions from Vijay (he just provided as a follow-up):

Padding will work just fine. Royal-Lac Post Cat cannot be used for French Polishing since the solids content is 40% and even if you dilute it, an applied coat will not dry fast enough like shellac and be ready for the succeeding coat. But this is not a drawback since in padding, coat after coat is applied after the previous coat has dried to touch. Moreover, if the padding is not the best it really does not matter since after cure the finish is usually level wet sanded and buffed.
May I suggest that you dilute finish by 100% for padding. For example, if you mix 14gm of finish and 2 gm of catalyst (7:1 ratio), add 16gm or more of denatured alcohol. This will cut the solids to about half. Feel free to dilute it more if need be. Also, no need to sand in between coats. Apply about 4-5 coats in a day and you’ll get a pretty good build. Wait for 24 hours and then if additional coats are required, apply as before. Allow 7-10 days to cure before level wet sanding and buffing.
A lot of luthiers have moved over to the Post Cat version since it cures faster.

Also, remember the excellent information collected by James Orr here:

viewtopic.php?f=10101&t=53922&hilit=Spray+Royal+Lac