Alright, this is what happened. I lettered a sign using one shot black, it's drying petty much flat with spotty areas of gloss. The temperature here was 20 degrees last night, high of 32 degrees today. I lettered this on white ACM material. I lettered it in an out building with no constant heat. I used a torpedo kerosene heater to warm up the building to about 50 degrees. Lettered the sign, looked great, nice gloss to the black. I turned off the torpedo heater and went inside and made a couple of runs. I got back and the out building was as cold inside as outside. The black still in the drying process was drying flat. I used turps to thin to a comfortable working consistency. Paint wasn't too thin but had good body to it. What happened in those couple of hours to the gloss????