Why is it burned so fast? I vape at max 10 Watts, coil is 1,25 Ohm Kanthal, 28GA so too high temperature or to high watts are not the case, my coils are heating up pretty slow. I am using unflavoured 15DW/85VG e-liquid so neither flavours are the case. My draws last from 2 - 4 seconds. Vapour production is still good, vapour taste is not affected (no burnt taste).
What is this black gunk or layer on the coil? What does it mean from health point of view?
How to resolve this issue? How often do you rewick your coils? How long does it take for your coils to get to this state? At which power (watts) do you vape?
Thank you for your answers in advance.
You shouldn't be seeing any discoloration at that power, with unflavored juice. I'll admit I have no experience cutting juice with water and don't know if that could be a factor, though I don't see how. If it were any commonly used combination of VG/PG all the way to 100% VG I could say you absolutely shouldn't see any discoloration.
Personally I find an 8 wrap coil of #28 with a 2.5mm I.D. works well with the kayfuns V5 run somewhere around 12W to 14W.
I'd have to guess its either your wicking or you haven't opened up the juice control enough. When you fill it and its screwed all the way down, you need to back off two full revolutions to have the juice control fully open according to Svoemesto.
Also a few other minor (in comparison) things play into juice getting to the coil in pressure differential tanks like Kayfuns, your juice viscosity, your draw and airflow settings.
If its the wicking, honestly you can watch all the videos and listen to all the advice in the world, but getting it right takes practice and repetition.
Anyway, check out Phil's video, it'll give you a good rundown of the product.