Thinning Conversion Varnish in Hot Weather

A finisher seeks advice on techniques for thinning conversion varnish on days when the weather gets hotter than 90F. November 29, 2014

For you guys that spray SW Kemvar Plus (the topcoat, 60% solids, V66V21 catalyst). We have been spraying conversion varnish for the past six months and thinning it mostly with standard lacquer thinner from SW. On warmer days I toss in some butyl acetate to avoid solvent pop. Our shop doesn't have climate control, so I'm interested in seeing what you guys use for thinning in really hot weather (90 degrees and higher). Currently, on an 80 degree day, I'm cutting it 35% with lacquer thinner and 5-10% with butyl acetate (total, 40-45%) and achieving good results. I'd like to perhaps get this down to a single chemical, something a little slower than the standard lacquer thinner, but obviously not as slow as the butyl acetate.

Forum Responses
(Finishing Forum)
From Contributor F:
You should contact your ML rep. They have several lacquer thinners available to deal with temp and humidity. I spray Duravar and start to switch to retarder over basic thinner in the summer when it's hot and humid.

From Contributor R:
Id contact Sherwin Williams about the product. Maybe ML has the same formula as SW does but who knows. Aside from reducing the material, keep in mind the VOC threshold. Some states have stricter laws than others do so stay within the limit when you reduce it. California, for example, is known to have Air Quality officials drop in unannounced to view the finishers record keeping. They also will take a sample of what youre spraying back to their lab for testing. If its over the limit be prepared to open your wallet.

From the original questioner
I do appreciate the suggestions here, but I asked the representative these questions before I ever bought the first gallon of the stuff, and they gave me good suggestions, which have worked in this weather so far. My rep has never sprayed this product for a living, 40-60 hours a week, in 90-100 degree temperatures, so he can only tell me "should work, might work, supposed to do this, supposed to do that". I'm looking for the opinions of folks who are actually spraying it.

Regarding the law, we are in complete compliance with every law we are aware of, we have sought out what laws we are to follow, and we do not hide behind ignorance. Our shop is about as geographically, politically, sensibly, ideologically, and intentionally as far from California as one could get, and still remain in the continental US. I doubt quite seriously that Kemvar Plus is sold in California, and even if it was, I doubt that anyone could spray it if you're not allowed to thin it, unless you have equipment that is capable of spraying peanut butter.

From Contributor R:
Kemvar Plus is available for sale in California and can be reduced with a solvent called Oxsol. It and acetone are exempt in that state. Not to get into a discussion about politics that pertain to coatings, but lacquer thinner might not be the best solvent to use. Usually Xylene is used and it wont dry as fast as lacquer thinner or acetone will so it may help retard the dry time and give you a better flow. The oxsol even dries a bit slower. Application wise; an airless works well. Shops in California who want to follow the VOC limits to the letter use one.

From the original questioner
That's the sort of info I was hoping for. I will order some xylene and try it out.
I am actually a bit surprised that you can get Kemvar Plus in California. It's a pretty intense solvent-based finish. We run two AAA pumps, by the way, agreed with you on that.

From Contributor R:
Strange as it seems California has different VOC limits and they based on the county your applying it in. The Kemvar has a VOC of 367 but once you add the catalyst (which you obviously must do) it kicks it up to 535. Add a thinner like lacquer thinner and it boosts it up even more. Add as much acetone as you want. (its an exempt solvent). Reduce it with xylene and it brings you over the VOC threshold. Oxsol is an exempt solvent and will flash off at a slower rate than L/T or acetone or xylene. You might want to try it.

From contributor K:
There is a special reducer for the Kemvar Plus called Kemvar Solvent (R7K310). Its pretty expensive though, so I just use just premium grade lacquer thinner at 50%. I also spray a clear cv topcoat over that to add depth and durability (makes touch-ups easier too without small scratches going through the color). I find that when using the Kemvar Plus as a topcoat, the Kemvar Solvent is key to achieving fantastic results. But again, I just do wet on wet passes with the color then the CV topcoat. It turns out real nice.

From contributor D:
I thinned 40% with xylene, but had issues with inconsistent sheen (spraying low gloss). I talked with the rep, but no one could give me a good solution, so I switched to Chemcraft CV. Not as good as original SW kemvar, but a lot better than trying to thin that five gallon bucket of toothpaste from SW.

From contributor M:
Spraying the KV Plus can be a touch tricky because it's such a high viscosity finish, especially cutting it 40%. It's designed (according to their information sheet) to be thinned 50%. Since it can be sprayed on in heavier coats (which is almost required at 40% thinning because of the viscosity) then you're probably getting a lot of flattening paste that is settling back into the film rather than staying in place.