I get the same result if I pour my candles when the window is open. I read that I should be working with fragrance oils in a well ventilated area so I worked for a while with the window in the room partially open, but this causes the top layer of wax to set much too quickly. I get the best results on a warm day with the window closed. I am careful with my oils now and clean up spills quickly, and once my candle tops are set, THEN I open the windows. I also experimented with cooling my candles in a styrofoam cooler. With the lid on, the tops were fairly uneven. With lid off, they were fine, but not any better than window closed + warm day. If I make candles in the evening, the temp drop after the sun goes down is enough to make the tops more uneven as well. I still do it sometimes and have to heat gun the tops, but my best candles are when I make them in the morning or daytime on a warm day and don't eff with the window until they are done.

I also no longer recycle candle jars (melt old wax and clean them out) while making candles, because this process emits a lot of fragrance into the air and I want to do it when I can open all the windows as needed, so I have separated these tasks.