Here are the photos of the front and back side:
The first and the easiest way to tat this would be tatting the first chain with a number of normal picots and connect the second chain to them with Catherine Wheel Joins. However, this way has a serious drawback - the second chain will not be connected to the part of the first chain that is _above_ it, and spiral will loose the form when you try to move the tatting (e.g. using spirals in earrings).
That is why I decided to use downwards picots also. In fact I used some kind of joins that I can't find a name and description. They are something very similar to CWJ but the picot is _above_ the chain, not _below_ it. I hope that it's enough to understand what I mean, but if it is not, I will make a set of photos to show it.
So, some abbreviations:
p - picot
dp - downwards picot
CWJ - Catherine Wheel Join
DCWJ - Downwards Catherine Wheel Join (the join I described earlier).
You start tatting from the back side (!). At the picture the first chain is green.
Ch 8 dp 8 dp 6 dp 4 dp(#2) 3 dp(#1) 2 p(#2) 1 p(#1) 1
Then you change shuttles and turn work, and tat the following:
Ch 1 DCWJ (dp #1) DCWJ (dp #2) 1 CWJ (p #1) 2 CWJ (p #2)
This is the necessary part - tatting the middle of spiral this way you make it stable enough. Continuing tatting this spiral you should do all these steps at the same time:
- Tat (4 CWJ) till the end, where CWJ is connected to the space between stitches (we didn't do more picots on the first chain).
- Tat (DCWJ) instead of ds when needed.
- When you reach the point where the first chain started, make a simple join.
- When you reach the point where the spiral should finish, make a lock join.
Well, I hope that my explanation was not very boring! The only thing I want to add is how to change the size of spiral - you can add as many groups (8 dp) at the beginning of the first chain as you want.