Conversion Varnish Pot Life and Durability
Does extended pot life (days or longer) in a conversion varnish come at the expense of other desirable qualities? July 7, 2011
Question
I see there are companies that make conversion varnishes with pot life in the 14 - 21 day range. I am used to using CVs with an 8-10 hour pot life. Is there a drawback to using a CV with a 21 day pot life, like decreased durability? It seems like whenever you gain convenience, you lose some performance - is this the case with the extended pot life?
Forum Responses
(Finishing Forum)
From contributor B:
Since I'm the guy making the 21 day pot life [Gemini], I'll tell you how I feel about it. You can't let the longer pot life fool you into thinking performance is lacking. If it were, they would not be accepted in the market as a CV. And no, they are not pre-cat lacquers (to those competitors who can't figure out the chemistry).
Get some of each one of the pot life CVs you are thinking about, including the one you currently use, spray out a few drawer fronts, let them cure for 10-14 days and stick them halfway in a bucket of water for three days. You'll see that they hold up just fine.
From the original questioner:
Are they also just as chemical resistant? I like the idea of the extended pot life, but I want to make sure I am not giving anything up as far as durability is concerned.
From contributor J:
Cross linking chemistry has come a long way for sure. There are some factory or distributor catalyzed "pre-cat" finishes on the market that are almost at the level of a true CV in terms of durability and resistance. Some have a pot life of up to 6 months after being catalyzed.
What I don't get is the big advantage of 21 days over 8-12 hours? Is this product catalyzed by the user or the distributor? Seems to me it would be easy to forget when exactly your 21 days is up if you forget to mark the can. I would be skeptical about other issues too, like variations in gloss or application properties as the product nears closer to the end of its pot life. I’ll stick with my 8-12 hour CV and just mix what I need to spray in a day as needed.
From the original questioner:
I agree - I wouldn't spray a CV that has been sitting around catalyzed for 20 days either. But I think the advantage would be you will save a lot of time and material in the long run. If you spray for several days in a row, you won't have to flush the gun out with thinner everyday, or dump out leftover finish at the end of every day. You could just run the finish down low every day, and mix up fresh every morning, just take the tip off the gun each night and let it soak.
From contributor J:
That's exactly why I use pre-cat for 80% of my work. I only break out the CV when I know the finish will be subjected to higher than normal wear and moisture or when it's customer requested. Personally I think CV is kind of overkill for some applications. After all, do you really need a finish that can't be stripped with lacquer thinner on everything?
From the original questioner:
Yes, I agree CVs are overkill for a lot of projects. But almost all of our work is either kitchen cabinets or bathroom vanities, for which I feel CVs are a must. We do build mantles and entertainment centers, but they go with the same job as the kitchen cabinets, so it's just easier for us to spray everything with the same finish. I think the extended pot life will also make it nice for us when the contractor calls two days after we deliver a job and tells us he needs an extra piece of trim. There's nothing worse than having to mix up more finish for 1-2 pieces that got left behind. We can just leave the leftover CV for occasions like that. Extended pot life CVs may not be that useful to some shops, but for mine, I think they will be very handy.
From contributor J:
Not to argue the point - I agree CV is great for bath cabinets - but most of the kitchen work I do is pre-cat. I think a lot of finishers out there got a bad impression of pre-cats from one particular product that was very popular until it had a lot of moisture related failures. Not all pre-cats are created equal. Some are not much better than nitro lacquer, while others are almost as good as CV.
To put it in perspective, my own kitchen and bath cabinets were finished with pre-cat vinyl sealer and pre-cat topcoat 12 years ago and they look as good now as when they were new. But then I don't have 5 kids and 2 dogs either.
From contributor D:
Contributor B, it is nice to have the chemist chime in here. Does your 21 day CV contain nitrocellulose? This is one way I have separated a true CV from a post catalyzed system in the past. The product we use is Becker Acroma, which has a 24 hour pot life and no nitrocellulose. I would be interested in trying your product versus our current system for performance.
