Overall, nicely done! I can see a great deal of growth and improvement over the set. I can see some issues that came up as well - one of which you sorted out as you worked through the set, and one which still appeared to persist until the end.

As a whole, I am very pleased with the keen observational skills you demonstrated throughout this challenge. You really got in close and identified all of the subtlety of your reference images, showing a great deal of patience and care. You didn't fall back to drawing from memory, and instead focused on identifying only what was in front of you, pulling from it directly without further mental processing.

Your textures also show that you clearly understand how every surface you were dealing with is made up of solid, 3D forms, and how every mark implies their presence. It is common that students working on this exercise will, especially when they demonstrate observational skills as fine as what you've shown here, get too caught up in just drawing what they see. You've clearly gone beyond that and understood the forms that are present there, and how they might cast shadows on their surrounding surfaces.

So, the first issue that stood out to me was one you did end up correcting on your own. Earlier in the challenge you weren't quite as confident in your use of confident, filled shadow shapes, and instead used a lot of hatching/erratic scribbling/etc to try and create the midtones you wanted so badly to help promote your gradients. Of course, this is incorrect, both in that it didn't allow you to really push your observation (due to the randomness factor), and it also didn't allow you to be quite as decisive with your marks. I'm very glad to see that you resolved this - as you push from #10 onwards, you definitely lean in hard to the clear, intentional shadow shapes, defining their outlines first before filling them in, rather than just painting shadows onto the page more arbitrarily. This also helped imply the presence of clear forms as described previously much more effectively.

The other issue I wanted to discuss may have you knocking your head against a wall a little bit, because it's actually very obvious - the black bar on the left side of the gradient isn't there just to look nice, or to separate the gradient from the rest of the challenge. The purpose of the challenge is to achieve a smooth, seamless transition from the solid black bar on the left to the area of solid white on the right. In most of your textures here, you jumped very suddenly from the black bar to your texture. There were a few, like 16, where the edge of that bar got somewhat obscured (which is a big move in the right direction), but you basically need to work on expanding the dark end of your texture and allowing your cast shadow shapes.

The beauty of working with cast shadow shapes is that they are flexible. By simply saying, we're turning up the light, turning down the light, or moving the light around, we can allow those cast shadow shapes to start to deepen - getting bigger, covering more surface area, expanding to merge with neighbouring shadows and plunge a section of texture into complete darkness. As we pull back on this and allow more light in, those shadows get shallower, pulling back closer to the forms that cast them, and opening up to areas of solid white. We can control them completely in this regard. You definitely do understand this - aside from the darkest areas, your density gradients are excellent, and you show remarkable control of it towards the white end on the right side. You just need to push the darks harder.

Just as a reminder, this diagram from the texture analysis notes goes over what I've explained above.

So! As a whole I am very pleased with your results, and while you do still have room for growth, you're making excellent progress. I'll go ahead and mark this challenge as complete. Keep up the great work.