Replies

1. 
   Kevin | May 22, 2003 05:37pm | #1

   Hey... a fellow Northwesterner! :-)

   Here's how AWI (Architectural Woodwork Institute) defines conversion varnish: "A catalyzed alkyd-based coating that is tough and resistant to household chemicals." AWI doesn't define Alkyd, but the Sherwin-Williams Chemical Coatings Finishing System Guide does. "Alkyd: A synthetic resin which is made by the reaction of a polybasic acid, such as phthalic, maleic or succinic acid, with the polyhydric alcohol such as glycerine. Vegetable oils, fatty acids and other resins are often used as modifying agents." DuPont's Chromasystem Technical Manual has a less detailed, but somewhat easier to understand definition for Alkyd: A coating based on a polyester binder. Such polyesters are chemical combinations of molecules that contain more than one acid or alcohol group. Typically the alkyd finish is catalyzed with an acid so that adding the catalyst is what completes the formula and makes it a conversion varnish.

   What makes conversion varnish "good" is a matter of what properties one is looking for in a finish. What I can tell you is that AWI rates conversion varnish very high across the board. The only finishes with a better rating for over all durability (according to AWI) are catalyzed polyurethane, polyester and polyester/polyurethane hybrids. For over all rating only the catalyzed vinyl rates better, and that only slightly. However, Sherwin Williams rates it's conversion varnishes slightly better on an overall rating than it does it's catalyzed vinyls. Sherwin Williams treats the catalyzed vinyls much like conversion varnishes, lumping them all together under the "Kemvar" grouping. Both finishes are catalyzed with acid and contain formaldehyde. Catalyzed vinyls also contain alkyd resins... at least SW's do.

   As for how nasty a finish it is... I presume your painter meant that it's nasty in terms of health risks. That's all relative IMHO. The more durable the finish, the more health risks are associated with it's use... in general. Also, the more durable the finish, the less user-friendly it is to touch up or repair... in general.

   If you've got the spray equipment, a place to spray 'em at and a good respirator then I don't see any reason why you couldn't use it just because you don't consider yourself a professional. It'll spray like lacquer.

   FWIW... I personally prefer precat nitro-based lacquer as a happy medium between durability and ease of touch up and repair. That's my default finish unless a customer stipulates that I use something else. I've got a job coming up in a week or so where I have to use catalyzed vinyl 'cause that's what the client stipulated because it's going to be installed inside the arctic circle and cat. vinyl is better suited to cold check resistance.

   Greetings from Portland,

   Kevin

1. 
   DennisS | May 22, 2003 06:15pm | #2

   Kevin -

   Thanks for the explanation on the make-up of conversion varnish(es). From the chemical composition, sounds like I'll stick to mineral oil & beeswax (grin).

   Seriously, though, it was the health risk issue I was refering to when the painter described it as 'nasty'. For what little I'm doing that requires a durable finish, I think there are other more rookie-friendly approaches to getting a satisfactory end result.

   Thanks again for the explanation.

   ...........

   Dennis in Bellevue WA

   [email protected]

1. 
   HowardAcheson | May 22, 2003 06:55pm | #3

   Dennis, I suggest you get the MSDS from Sherwin William on their CV. See if you want to deal with the risks.

   As I recall, it is required that you use a forced fresh air respirator for safety. Standard respirator filters may not be effective.

   I personally do not feel it is a product that anyone but a professional should be using.

1. 
   Kevin | May 22, 2003 08:26pm | #5

   The MSDS may well stipulate the use of a forced air respirator system. But, the current product data book that I have says that either a standard (with the appropriate cartridges) or forced air system can be used with conversion varnish.

   FWIW... my opinion is that the question of whether to use conversion varnish or not should hinge on whether one has a spray booth or appropriate exhausting system. I definitely wouldn't spray this stuff in a garage. Although I know guys who do.

   Regards,

   Kevin

2. 
   DennisS | May 23, 2003 02:48am | #6

   Kevin; Howie -

   Thanks for the info on this stuff. I don't think it's in my future to be using it - I asked out of curiosity as much as interest in actually using it. No need to use bandwidth on the discussion as far as I'm concerned. You've all pretty much answered my question(s).

   For the record (sorta), I used a waterborne poly finish on a redwood countertop for the new landry sink/tub and it's looking really quite nice. Time will tell with respect to durability, of course. That's the first time I've used that particular material and for me it was great stuff to work with. Easy cleanup, flows on nicely and quick drying time to re-coat.

   ...........

   Dennis in Bellevue WA

   [email protected]

1. 
   TomT226 | May 23, 2003 02:19pm | #7

   Try Target PSL. It's a water based lacquer that has 100% burn in, and once cured, has almost the same hardness and durability of conversion varnish or CAB lacquer. I use it all the time when I don't use nitro lacquer.

2. 
   Kevin | May 22, 2003 08:19pm | #4

   Dennis,

   As I understand it the primary health risk associated with conversion varnish is the solvents and especially the formaldehyde. SW does offer a water-based version which would get you away from the vast majority of the solvents. But, it still has formaldehyde in it. Keep in mind that alkyd resins are used very widely in finishes from stains to clear coats. That's not to say that alkyd resins have no health risks... I assume they do to some extent.  It's just that the alkyd part of conversion varnish's chemistry isn't the primary health risk.

   Regards,

   Kevin