Conversion varnish primer
pot life and durability. May 2, 2001
I have been thinking about switching from Sherwin Williams' moisture res lacquer to their conversion varnish for a more durable product. I am using HVLP and a 2 gallon pot. I can leave lacquer in the pot for days without a problem. With conversion varnish, do I need to clean the pot and hose out at the end of every day, or can it sit overnight and still be usable?
It's a different ballgame between lacquer and conversion varnish in a pot. You need to clean out lines at the end of the day to be safe. It depends on the conversion varnish, chemically. Some have more than a day pot life. Some have a lot less. It depends on temperature, also.
The biggest concern is that if you use the pot with conversion varnish and do not have a stainless steel pick up tube on the pot, the CV will yellow out if you are using a water clear. The acid reacts with the metal on a normal pot tube.
All CVs have a different pot life, depending on whose product you're using. Most go from 8-24 hours and need warm temperatures to cure properly. They are a huge step up in performance compared to conventional lacquers. An alternative would be a pre-cat lacquer/varnish--these have shelf lives of several months and are good performers. SW does have a new pre-cat on the market. These you can leave in your pot.
I'm going to side with Joe on this one. CVs, especially SW's water white, are great products if you have two things. Warm weather and the ability to use them all up after catalyzation. Not a problem if you use gravity feed guns, as I do. With pots you are better off with a good pre-cat. Velspar, Lilly and SW all make good pre-cats that should get the job done for you as they all pass KCMA tests. With your equipment set, this is probably the best solution.
I have had problems with the SW CV flattening agent settling out in a 2 gallon pot and 25 foot hose, unless I am spraying constantly and/or it is stirred in the pot.
We use Duravar on a daily basis. If we have some left at the end of the day, we blow the line back and have never had a problem. If for some reason I will not be topcoating the next day, I will go ahead and thoroughly clean it, which is easy with plastic liners.
Yes, the flattening agent does tend to settle out of it, and an agitator set up would be the ideal thing. But, it's all a matter of knowing your product.
As for left over material, it becomes sealer. As it does not turn to jelly in a 24 hour period, we spray cabinet backs and back of trim with it to use it up. Our rep has informed us that it just tends to lose some of its chemical resistance and is just fine for this purpose.
From the original questioner:
I want to use the finish on kitchen cabinets in a small shop. Would the pre-lacquer be as durable as CV?
They are not as durable, but as mentioned earlier, they're an alternative. Most cabinetmakers I know prefer a post-cat coating, but I do know of a few that use pre-cats. Contact some suppliers and gather up the info and run some tests.
How long will you leave the CV in the pot? Generally I'm against cleaning the lines at the end of each day; what a waste and danger. Talk to your rep about decatalyzation procedures at the end of each day and uncatalyzation for weekends. Introducing thinner into the lines is a contaminant. Sure, you may not have a problem now or in a few months, but you will someday.
Use SWs' tf3 vinyl sealer; you don't need to cat this product if wrinkling isn't a problem or critical re-coat isn't a problem. The benefits for catalyzation in intercoat adhesion are minimal for this product, anyway. Then you only need to cat the CWW CV topcoat. All stainless or pure aluminum, otherwise carbon metals will spend the catalyst and it may not be there for all stages of curing when you need all you can get.
Get your rep to explain all of this to you. The CV finish offers your customers a good advantage to chemical resistance and a higher build with one coat for wear. However, I will argue the finer points of the tf3 vinyl sealer as being great moisture resistance, but it is an improvement over NC sealers.