Great info. I have a question, how do I get the ohms up to around 2.1-2.5? I am using 30 gauge and 2mm silica (newb,lol). I will eventually get to cotton but I've only wrapped a couple so far and I am at 1.2-1.3 ohms with 4-5 coils. Do I simply just need to increase the amount of my coils? That doesn't seem right since your wrapping 10-12 and still getting that low ohm. Obviously the size of the coil has much to do with it also?
Interesting info, when you say mandrel, is it the typical wire looping type that is graduated to different diameters all the way up? If so, wondering how you decided to use that instead of what I have read so many say they use such as drill bits, etc?
A drill bit can be a mandrel... as can a toothpick, paper clip or needle. So, when I say "use a 1.5mm mandrel" - it means for you to use anything that will suffice as a mandrel with which to wrap a wire coil of a specific size, and yet... not specifically a drill bit.
The difference is most micro coils are around 1.5mm mandrels and are wrapped tight around the mandrel with the wraps touching each other.
The easiest way to explain the relationship of resistance and wire gauge is that the thinner the wire, the higher the resistance. And when you wrap wire around a smaller mandrel you can use more wraps and still use the same amount of wire, meaning the resistance is the same. When you wrap coils with spaced out wraps you will end up with less wraps and still have the same resistance.
If you have a smart phone, check out Vaper's Toolbox, so far it has been fairly accurate.