Acid Catalyzed Lacquer

[gellkeller]

I posted this in the "Vibrola" section but nobody bit. Hopefully someone can shed some light.

Is "Acid Catalyzed Lacquer" a pseudonym for Conversion Varnish?

[henry5]

My first 2 Sei basses had the above finish, but unfortunately I don't know anything about it other than in their case it was a satin finish and easily repairable.

[jingle_jangle]

Catalyzed lacquer, in my experience, is peculiar to Asian-made instruments, and is an offshoot of the Korean (and later, Chinese) high-volume piano industry. This is a polyester finish, and in theory works like a CV finish, but is almost always pigmented because it does tend to yellow with time. It's cheaper than CV, less chemically complex, but cures to a very hard and brittle surface and is usually applied about 3-4 times as thickly as CV is. It is a stone bear to flatten and buff, and once cured will even resist chemical stripping.

CV is more ductile or impact-resistant, and is a higher-quality and more chemically sophisticated.

[gellkeller]

Paul, thanks for the info.

Would the catalyst have any bearing on the quality of the finish? Is an acid the preferred or only type of catalyst?

[jingle_jangle]

Practically speaking, the catalyst in this type of paint has no effect on the quality of the final surface, provided it is mixed in proper ration and the finish is applied correctly. Since this is a polyester (not a polyurethane, as is CV), the ideal ratio is 2% catalyst, but I've seen cases where the ratio has exceeded 10%, which still cured and yielded a satisfactory finish. This is not possible with urethanes; the ratios with these and with epoxies are much more critical; being off by a small percentage yields a finish with substandard performance.

This is the reason when I hear amateurs and some professionals talk about "poly" finishes. I respond, "Poly what?" and usually then see a confused look on the other's face. Polyesters and polyurethanes are two very different animals.

An interesting tidbit regarding polyesters: The "catalyst" in polyesters is not, strictly speaking, the agent that reacts directly with the resin in order to effect a cure. Rather, the material itself would cure by itself in air, if an inhibitor was not formulated into it.

The catalyst (methyl ethyl ketone peroxide, or "MEKP") actually strips away the inhibiting agent to allow the resin to react with the air. Additonally, cobalt promoters are usually added to the MEKP to facilitate cures at room temperature.

Gary Clauson, being an organic chemist, could be more specific on the reactions involved here. My experience is practical and I've only done a bit of reading on this topic.

[gellkeller]

Paul, I really appreciate the time you spend on answering these types of questions. Informative, concise and educational. Much appreciated