Question
I have been spraying Sherwin-Williams Kemvar water-white conversion varnish for 4 years with great results. On the last 3 jobs, the finish has wrinkled once I sprayed the first or second topcoat over clear vinyl sealer.
I have followed all the manufacturer's recommendations for catalyzation, reduction, etc. The problem seems to occur most with stained wood (I use only Sher-Wood wiping stains), but has also cropped up on pieces receiving a natural finish. My shop does tend to be humid.
The sealer is catalyzed. The time between coats varies from 6 to 24 hours. I'm not mixing old and new finish, but I will use the same batch until it is around 24 hours old. Sanding with 220 grit between coats. Wet finish thickness is between 3 and 4 mils. Wrinkling patterns are quite random, but seem to appear more frequently where spray pattern overlaps. I have tried sanding down to bare wood and starting over, but it doesn't seem to help. Shop temperature is generally around 75 degrees in the summer.
Forum Responses
Rule #1: Do not use CV
Rule #2: If you must, do not use a sealer.
Rule #3: Mix your batch, wait 30 minutes to let the material anneal and fog on your first coat, apply a heavy coat, 320 and scotch brite and final as soon as your sanding is done, with a good shot of retarder.
CV in the olden days had a terrible re-coat window problem and became seedy with age. The longer you wait after the product starts to crosslink, the larger the cross-checking is going to be. Also, sometimes CV can not emulsify out 220 scratches. Your problem is that the solvent in the new coat is eating into the drying film below. Switch to a better product.
Also, are you using their W/W catalyzed vinyl sealer? I tried that stuff a few years ago and thought it was awesome.
Your sealer may not be put on wet enough or maybe just a little too thick or drying too fast and not getting a good bond to the wood. Take your topcoat and use it as a self-sealer. Probably cut it 1:1 with the reducer. Spray a couple wet coats, let it dry long enough to sand, then re-coat with your topcoat. Also test it, letting a piece dry overnight and re-coating the next day on the same type of wood with the same type of stain underneath. See what happens. If no problems, your sealer was in fact your culprit.
Be sure you’re putting the right amount of the correct catalyst in the material. You’re either not getting a good bond with your sealer or your sealer is too soft. What’s happening is your topcoat is pulling it all up when it starts to cure and the catalyst in the topcoat is giving a little time to attack the sealer also. Using a sealer under the topcoat is a good thing, but your sealer has to be compatible.
