Just tidying up a beat-up headstock on a low-priced Hamer. I sanded it and hit it with a thin coat of acrylic, and it looked good. Steel-wooled it two days later and did the same. Looks great, until you look close and see the crazy little cracks. What would have caused that? My little workroom can get cold at night, and I probably did this around midnight, before the heat went down to about 57 or so. Could that be it? What else? Spray too thick? I'm sure the previous coat was quite dry.