Question
I've been using Chemcraft pre-cat lacquer for awhile now and haven't tried anything else. I see a lot of people using CV. What are the advantages (ease of use)? I'm using a Turbinaire HVLP with a 2qt pot and Turbinaire gun. I can't seem to get that glassy look and feel. Would using CV help that?
Forum Responses
(Finishing Forum)
From contributor D:
Pre-cat vs conversion varnish... You raise three issues:
(1) Ease of use. Pre-catalyzed lacquer is much more user-friendly than conversion varnish because conversion varnish must be catalyzed by the user prior to use, measuring in catalyst in precise quantities and sometimes letting the stirred and catalyzed mix "dwell" (sit for minutes while the catalyzed coating starts the reaction). Pre-cat needs no dwell time because the catalyst is part of the mix before you open the can.
Conversion varnish has pot life issues of 8 hours to weeks depending on the manufacturer of the coating and climate conditions. Gemini Coatings has been making a 21-day pot life CV for the longest time (longer than 21 days) and it has an excellent reputation as a coating, as does Gemini as a manufacturer. Pre-cats have no pot life issues but they do have shelf life issues from 90 days to two or more years, also depending on the brand and specific product.
Conversion varnishes could stay wet for more than 35 minutes depending on the brand (you must read the spec sheets for every coating that you use). Pre-cats handle like traditional lacquer and flash in maybe 20 minutes at the longest.
Some conversion varnishes have recoat windows that you have to factor in. Your spec sheet will tell you what and when. Even so, ambient conditions and/or operator error can quick in a recoat issue for any catalyzed coating, CV or pre-cat. The symptom? Wrinkling of the undercoat.
Conversion varnishes are 85% cured within about two days of their application. Pre-cats take about 3 to 4 weeks to achieve a cure that is worthy of any kind of performance. This is a performance issue and not an issue of when your sprayed parts are going to be ready to stack or pack (that would be a drying issue and I already touched on the flash times and spec sheet aspects of figuring this out).
(2) Advantages of CV vs. pre-cat. CV's are usually tougher and perform with more durability than pre-cats. Depending on the pre-cat, the differences might be nominal to minimal or they could be vast. Some pre-cats, once fully cured, are almost as tough as any CV. Most CV's are non-yellowing. This is not always an advantage but it is a feature and something to consider.
CV's have higher solids ratios per weight and volume of applied coating. It takes less of the catalyzed product to build more mil thickness. One little factor not considered by many end users is that the amount that you catalyze the product, you reduce the coating's resin content, e.g., adding in 10% by volume of catalyst to a coating which has at its outset 28% solids reduces the coatings solids content down to 25.2% solids by volume (28 - 2.8 = 25.2).
A disadvantage of a CV that specifies xylene as its reducer is just that, exposure to xylene. Xylene and toluene are two things that you want to protect against and avoid. With proper precautions and care this is no issue. With inexperienced and reckless operators and such, they run health risks down the road.
(3) The glassy look. If you cut down on the production issue and thin/reduce your coatings more (thinner build per sprayed pass) then you will lay down better quality coats. But you will need to lay down more of those coats, hence the sacrifice in production. This is where the air-assisted airless spray delivery systems seem to excel, laying down incredibly smooth off-the-gun coats of unreduced material. In that many CV's today seem to handle like lacquer in terms of flash times, stack and pack times, but not the time it takes for full cure.
One coating is not better than the other. It depends on many factors and it's up to you to weigh all those factors and certainly know what they are. It's all about tradeoffs, pros and cons.
1) CV is a lot more chemically durable than pre-cat. A lot - trust me on this. I have poured lacquer thinner onto drawer fronts sprayed with CV and cured 24 hours. Let the thinner evaporate - no effect. Do that to pre-cat after a 24 hour cure, see what happens. Most likely the sheen will be severely messed up, perhaps some wrinkling.
2) Krystal thins with regular lacquer thinner, not xylene.
3) Krystal stinks to high heaven, but so does pre-cat.
4) Krystal is a good bit higher in solids content. If you are using a good AAA and don't thin more than 10% or so, you should be able to get a spectacular finish in two passes.
5) Krystal has a sealer available but it's not needed. Krystal sands very well after curing up. Much better than pre-cat.
6) Krystal has an 18-month shelf life (uncatalyzed) vs. the 4-6 month shelf life of pre-cats.
7) Krystal is available pigmented (called Stealth) just like pre-cats. It's also extremely durable.
8) CV never blushes. Pre-cat will sometimes, given the right situation.
9) Doors/shelves sprayed with CV can be stacked after an overnight cure with the utmost confidence, even in 100-degree Carolina heat. But I've had pre-cat stick together shelves and doors on hot days even after a good cure.
The only reason I'd use pre-cat is if I were a penny-pincher in a hurry. It's a good product, but give yourself time and you'll quickly discover that the quicker cure time of CV, the sandability, the much better durability, all make CV the stuff of choice.
Contributor E, thanks for the info. Part of the problem I've had rubbing pre-cat is likely because I've mostly used Opticlear and Magnamax, both of which are top-notch in durability, meaning hard to rub out. That's for sure.
