Troubleshooting a Sagging Water-Based Varnish
Use a higher viscosity product or try the "tack on tack" method, say the pros. October 2, 2005
Question
I am using my first 5 gallons of Target wb conversion varnish. It's nice stuff, but does anyone have trouble with sagging down the edges of doors? I get a real nice smooth finish when the work piece is horizontal, but on the vertical edges of my doors, the finish sags and beads up on the bottom. When dried, I get a ridge. I tried varying thicknesses of film, but it seems like if I lighten up too little, I don't get a smooth film and a tad more than that, it runs.
Forum Responses
(Finishing Forum)
From contributor J:
What size needle/nozzle setup are you using in your spray gun?
From contributor B:
Keep your wet film thickness at 1-2 mils, or use the "tack on tack" method of applying the 8000cv. This is a common practice for vertical sag control when applying low to medium viscosity coatings.
From the original questioner:
I am using a Sata K3 with a 1.2mm nozzle. I tried the tack on tack method without much improvement.
From contributor J:
Give me a call at Target and we'll walk through this together.
From contributor O:
Try a higher viscosity product in addition to or as a substitute for the technique of wet on wet. Eventually you will want to use both.
From contributor A:
Could someone explain the "tack on tack" method? I've been spraying WB finish for about 3 years and constantly battle sagging on vertical surfaces. If I spray a little too thin, trying to avoid sagging on complicated pieces, the finish feels rough, almost more like overspray on a completed piece. Using a Kremlin air assisted airless with tip size recommended by supplier of the Chemcraft Aqualux I'm using.
From contributor B:
Tack on tack is a spray method that uses a very thin/fine application of finish to create a uniform film formation. It is a method that I learned early in my finishing days when using NC lacquer and the older 2-part polys. Basically, I cut back on my fluid volume until I get a very fine, almost rough finish on the surface, wait for it to get tacky, then apply a second coat in the same method. The solvents in the second tack coat melt the resins of the first coat and create one uniform layer. Frankly, some finishes level better than others when using this technique, i.e. NC's that flash very quickly. Some WB's can handle this process, mainly the all acrylic products with a very short open time. Some WB's will just slide right off of a vertical surface because of how they are designed and the type of solvents used, regardless of how lightly you apply them. I get the best results from Target Ultima Lacquer and EM8000cv. There are other products on the market that can also handle this method, but I stick with these two products because they work well for me and I have found the company to be very helpful.
