My liquid darkens, what does it mean?!
Well it can mean a lot of things, the worst is that some chemical substances are burning on the coil or the coil burns itself because it’s dry. Either way, you’re inhaling burnt wick or something that even Panoramix doesn’t know. The other option is that the coil needs cleaning, sometimes it burns just a little every time you get new liquid, so cleaning it is somewhat a routine you should follow every day.
Third option, and that happens only with the highest quality liquids (so probably 1% of them), the pharmaceutical grade glycol and glycerine are so sweet that they caramelise. Some say it’s impossible, others that obvious. I believe them both, it just depends on the liquid.