Flatter pattern

Despite aggressive blocking, this turned out lumpy. Based on math, the increase in stitches for each round ought to grow geometrically, but it only grew linearly. If your stitches are stretchier (either because of size or yarn), you may not need the correction or as much correction.

I haven’t tested it, but here’s what I think would give you a flatter blanket of the same size:

Start as described.

Triangle base sizes:
Rd 1: 20 sts
Rd 2: 28 sts
Rd 3: 40 sts
Rd 4: 56 sts
Rd 5: 80 sts

Note that there is one less round of triangles. But since the triangles are larger, it should work out to about the same size.

If you try this, let me know how it goes!

Why the lumps?

I was surprised to see this pattern get so lumpy, but I think I know what happened.

I happen to also be working on the Diamonds Shawl from Omdahl’s Crochet So Fine. The pattern right after that is the Spiral Wave Shawl. This blanket happens to be exactly the first six rounds of that pattern.

However, that pattern is done is a very loose gauge, so the too slow increase is not problematic -- it might even be necessary. However, that does not translate directly to the tighter gauge that my yarn and hook gave.

Note that for the first three rounds, the linear increase matches the geometric and round four is only off by six stitches. Rounds five and six are further off from what the math would predict, and that’s where my blanket started to be problematic, even with blocking.

The graphical picture shows the progression of triangles, through the partially shown round 5) assuming approximately square stitches.

Tunisian variant

I used a size H Tunisian crochet hook and used the Tunisian gobelin stitch1. Instead of decreasing as indicated in the inspiration, I decreased by skipping the chain on the return pass and pulling through the first two loops on the hook together and pulling through the last two loops on the hook together. This got rid of gaps along the border between triangles.

(Note that for the Tunisian variant with this decrease, I had to add an extra two stitches per base row to get the right number of rows per triangle.)

1 Inspiration: http://www.ravelry.com/projects/truonyxrose1/spiral-croch...