Breathing Protection with Conversion Varnishes
Finishers discuss respiratory health and personal protection issues relating to the application of acid-catalyzed coatings. October 27, 2005
Question
I've read many posts on this forum about issues with thinning CV and shooting it with an HVLP gun. My current set up is an airless system shooting unthinned SW precat with a rac5 switch tip. Can CV be shot with an airless and still achieve a quality finish? Will it still need to be thinned to a certain viscosity? How much slower will this process be compared to shooting precat with an airless?
Also, is there any difference on how quickly a respirator cartridge will break through? I've got everything worked out for production output and expenses for an airless precat operation. I can look at a job and know almost exactly how many hours, gallons and incidental materials it will take me to complete it. The idea of switching to CV will obviously throw all that out the window. About the only thing I know about CV is that the durability is superior and that our coatings rep says that the drying time will be about 5% longer. If anyone has made the switch from precat to CV, I’d appreciate any advice or lessons learned.
Forum Responses
(Finishing Forum)
From contributor A:
I've only sprayed conversion varnish, and I've mostly used an airless. I did use a nice HVLP system at another shop once, and was very pleased with the results, but airless has been giving excellent results as well. I've been using Chemcraft's Plastofix Plus with excellent results. I still have to thin it a little (5 to 10%), especially with the hot weather, to get a really smooth finish. A dual-orifice 412 airless tip seems to work about the best.
From contributor B:
We switched from precat to CV and back to precat, mainly because of the horrible off-gassing of the CV causing nose bleeds, shortness of breath, and coughing. We do have a code conforming booth, but even a couple days after spraying, when installing, it still gets to you. We only use CV on table tops and anything of that nature that needs the protection. Otherwise, three coats of precat is a good finish.
From contributor C:
Make sure your filter is rated for formaldehyde and keep your respirator stored in an air tight container. I would change filters at least twice a month. If you’re serious about CV long term, you may want to consider a fresh air supply unit. The SW CV is great, but very nasty for those who apply and work around it. I don’t think that airless is the right way to apply SW-CV. An HVLP system is the way to go.
From contributor D:
The life of a respirator cartridge is determined by how much contaminant is in the air, the humidity level of the air and the respiration rate of the wearer. Believe it or not, the average life is 8 hours of use. Storing it in a plastic bag will help. For long term, air supplied respirators are more economical, but are not very comfortable to wear.
From contributor E:
I hear this a lot about acid cure paints. It is not enough to exhaust the overspray. You must change the air in the drying area too. A small fan in the wall to draw the off-gassed solvents outside should be required in every shop. Most conventional coatings range from 22 to 38 percent volume solids. This means 78 to 62 percent of the initial volume of the paint film will evaporate during the first hours of drying. You can figure that spraying a gallon of product onto your job would release as much as three quarts of material into the air around the shop. That is the reason CV and precats are nasty - improper drying room ventilation. Formaldehyde is not the concern it once was. Most paint systems contain less than 1/10 of 1% by volume but paratoluene sulfonic acid in the catalyst is dangerous. That product is in a higher concentration, as are the common solvents required to maintain viscosity. Don't breathe that stuff. The warning label tells you these products will cause nervous system damage if chronically inhaled.
