Re-Spraying Over Old Conversion Varnish

      Suggestions for prepping an existing CV coat before re-applying. October 2, 2005

We had a request from one of our new clients to reshoot a set of cabinets that was finished by another shop (approximately 6 months ago). There is a ton of dust and debris in the finish. According to the cabinet shop, they used Sherwin Williams conversion varnish. Can we sand out debris using 400 grit sandpaper and reshoot using the SW conversion varnish over the top of the existing finish? My main concern is adhesion over time. This is going in a high-use residential kitchen.

Forum Responses
I have had to apply my coating (Camger Coatings) over about a hundred chairs that had SW's CV on them dating back as many as 3 years. These chairs were rejected for one reason or another and at the time they could not shoot the SW CV over them. The material would either wrinkle or they would not get any intercoat adhesion, depending on the age of the chair. When I started supplying this account, they asked if I knew of a way to apply pigmented CV to these chairs so they could sell them at a reduced price just to get rid of them. I ended up coming up with a mix of acetone (5 parts) and Butyl Cellosove (2 parts) that the sprayer would mist a couple coats of onto the chair. After about 1-2 minutes, the old finish would soften enough so that a fresh coat of CV would get enough bite to adhere. Acetone by itself would evaporate too fast to be able to soften the finish. The BC would slow it down enough to allow it to dissolve the old CV. Scuff the finish before applying the acetone mix. Test the inside of a door first.

I would clean them and scuff sand with 400 and re-coat with SW CV, as you said. We have done this many times using SW CV, and it works fine.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor S:
Be careful of the amount of dry mils you will have once the recoating is complete. To many dry mils will crack or craze later down the road. It's risky to exceed 5 dry mils of any conversion varnish.

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