Resources for conversion varnish

Learning the fundamentals of finishing with CV. September 2, 2002

Q.
Are there any books or videos out there about conversion varnish, which cover recoat windows, touch-up, etc?

Forum Responses
From contributor D:
There is no book that has the information that you are looking for on conversion varnish. For recoat window information, you have to consult the manufacturer of the conversion varnish that you are using.

By the way, if you are new to conversion varnish (even though we are heading into summer here in the Northern Hemisphere), for the fist 48 hours after spraying, you must keep the ambient room temperature where your sprayed project is drying at or above 60 degrees F. Failure to do so could leave you with a coating that is inferior or defective.

All other specific questions should definitely be addressed here at the Woodweb Finishing Forum. There is no better place to hold round table discussions on conversion varnish.

Touch-up can be done with either additional applications of conversion varnish (if your finish schedule allows, depending on your existing dry mil thickness of your overall coating) or with Mohawk/Star/Behlens precatalyzed aerosol lacquer. But the type of touch ups and the types of touch up products are dependent on the actual repair that you are trying to remedy.



From the original questioner:
Can you put conversion varnish over the top of pre cat lacquer?


CV, for the most part, will not go over anything that has sterites in it. If you think you are having trouble now, just try applying it over anything other than itself and vinyl sanding sealer. CV is also very mil thickness sensitive and prone to cat problems, depending upon whose product it is. These problems vary - some need to have very accurate percentages and some need to be mixed and left to start crosslinking for 1/2 hour. For instructions on how to tame this animal, it is probably best to find a talkative person that uses the exact CV that you do. The manufacturers are not using the product in the field.



There are some other things to consider as well. What projects are you going to be putting this CV on? What type of spray equipment will you be using?


From the original questioner:
Iím using an HVLP and Williams CV. Most applications will be on cabinets, furniture, window trim and interior doors. Is there a way to monitor mil thickness without guessing?


From contributor D:
1. The question was asked about coating precatalyzed lacquer with a conversion varnish topcoat. The answer is yes and no. Yes, you can overcoat the precatalyzed lacquer (use a thin, light coat of vinyl sealer just to have a type of barrier coat down to prevent the precat from wrinkling).

And no - if you create this hybrid of finish types you will have an overall inferior coating and you will not know how it will hold up or how good its protective qualities will be (definitely not as good as just the conversion varnish with no funky undercoating).

Your best bet is that if you have a precatalyzed finish already on an item, use more of that precat rather than lay down a different finish. Scuff sand first and keep everything within the allotted dry mil thickness for your finish.

2. You check the thickness of your coating by knowing the percentage by volume of resin in your coating applications (including your sealer coats) and checking how thick your applications are when wet by using a wet mil thickness guage. (A coating sprayed 5 wet mils thick that has a solids by volume of 20% yields a dried film of 1 mil: 5 X 0.2 = 1.0).



We are using Sherwin Williams Kem-Var W and are having very good luck with it! We build cabinets and millwork. We use a Binks cup gun at about 40psi. All of the coats are sprayed on as thick as they will go without running. Experience will teach you by feel and light refraction. Spray something that has a vertical surface, let set for a bit, and see if it has runs. If not, spray more; if it does, spray less.


We just started experimenting with conversion varnish. We used Valspar. We used the Valspar thinned down as a sealer, sanded the sealer and then applied the topcoat. I noticed the finish is not as smooth as lacquer. Are we doing something wrong or is this a property of conversion varnish?


The Global Resistovar is very good. Are you straining when you pour the finish into the gun? This is important. Also, CV dries slower than lacquer, giving dirt more time to get into the finished surface. A clean booth helps a lot.