Over a period of time, excess burnt
e-liquid will accumulate on the heating coil of clearomizers. This can be removed by rinsing under water and doing a dry burn. Here's a quick demo video on how to dry burn a clearomizer's heating coil.
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e-liquid flavors are a mixture of Pg (propylene glycol), Vg (vegetable glycerin), flavoring agents, and liquid nicotine. Depending upon when the
juice ingredients were initially mixed, the final product may require some time before it will provide the best flavor. Not all e-juices will require "steeping", which often just means shaking the juice and then letting it sit to age a little, allowing the multiple ingredients to meld together as one. Steep time is generally 1 - 2 weeks for best flavor.
This is not to say that you can't vape the juice upon delivery, you can. Just know that it may taste best if allowed to age a little. Many vendors will print a "birth date" or creation date on the bottle.