So I'm trying something different - I shot a coat of Behlen's Sanding Sealer on raw poplar which had been sanded to 220. Next day I sanded the sanding sealer with 320, blew it off and tack ragged it, and shot a coat of Nitrocellulose Under Coat. In some spots (corners) it appears that there are stretch marks - as if the undercoater shrank a bit to reveal sanding sealer underneath. Why would this happen? The two should be compatible - both thin with lacquer thinner. I had tried shooting BIN under lacquer, and although the results were spectacular, I'm a little concerned that there might be problems down the road. Everything I've read warns me not to use BIN under lacquer. I emailed Zinsser on Monday about it, but still no response. Any ideas? My goal is to fill in the grain a bit without having to resort to filler.