Surprise: Picks Per Inch

Amount woven yesterday: 2.5"
Amount woven to date: 27"

I decided to figure out how many picks per inch I was getting on a warp that was 20 ends per inch. When I checked, was I surprised! I am getting about 65 shots (or weft throws, or picks) per inch. No wonder the weaving proceeds at snail-like pace.

How on earth can I get so many picks to an inch on this warp?

In the first shed, warps 1 and 2 go up, 3 and 4 go down
In the second shed, warp 1 goes down, 2 and 3 go up and 4 (like warp 1) goes down.
In the third shed warps 1 and 2 go down, 3 and 4 go up.
And in the fourth shed warp 1 goes up, 2 and 3 go down, and 4 (like 1) goes up.

As a result, there are places in each shed were the thread will lie in the same shed as it did in the previous shed, and so will lie neatly next to the thread from the previous shed; and then there are places where it will lie in a different shed, and so will lie neatly on top of the previous thrown thread in those places. And with each of the four sheds, these positions shift by one warp end. Because there are always places where 2 warp ends sit on top of one another and so take the space of only one warp end. i 4 warp ends will take less space along the warp than they would have if they had been woven as plain weave.

Something similar happens in twill. Is this what happens with twill? Is this the real reason that twill is woven at a closer sett than plain weave and is treadled with more picks per inch than its plain weave equivalent?

My analysis of what is going on here has finally led me to realize why some people say to weave crackle at a twill sett! 30 epi is a tight plain weave sett for 20/2 but the twill sett would have been more like 40 epi. At left is a closeup of the fabric and you can see the kind of open cell effect that appears while it is on the loom. It almost a very very slight waffle-weave effect. There is a sense of texture or depth to the cloth.

I do not know what will happen when I wash and press the fabric when I remove it from the loom.. Nor do I know what would happen to this effect if I were to sett the warp closer. But I can see that I might explore different setts in weaving polychrome crackle such as this, though I am not sure about other kinds of crackle. On my next warp I have made a note to think about trying 30/2 silk at a twill sett just to see what happens. I cannot bear the thought of threading 60/2 silk at a twill sett...........

By the way, near the bottom of the photo there is a whitish streak across the warp And, if you look carefully you might see two more streaks as you move your eyes up. though these are less clear in the picture. These streaks are evenly spaces and are not treadling errors. This is what happens when I begin treadling the next block. I haven't yet figure out what to do to prevent this from happening it, so I am thinking of it as a design element! At least for now!