What does "solidification" mean in "his departure or farewell was a kind of solidification"?

Question

But I had to give up on that idea or hope, I had to wrench it out of my head and heart, or out of my cunt, as the women say back in Torre del Greco, and although I never completely gave up, somehow I understood Jack’s reluctance or his stubbornness, the luminous, fresh, honey-slow silence surrounding him and his few words, as if his tall thin figure were vanishing, and all of California along with it; in spite of my happiness, my joy, or what until shortly before I had thought of as happiness and joy, he was going, and I understood that his departure or farewell was a kind of solidification: strange, oblique, almost secret, but still a solidification, and the understanding, the certainty (if that’s what it was) made me happy and yet at the same time it made me cry, it made me keep fixing my eye make-up and made me see everything differently, as if I had X-ray vision, and that power or superpower made me nervous, but I liked it too; it was like being Marvilla, the daughter of the Queen of the Amazons, although Marvilla had dark hair and[…]

Excerpt From: Roberto Bolaño, in the story “Joanna Silvestri”, in The Return (story collection)

What is the meaning of 'solidification' in this portion?

Answer 1

There are many passages in this story where the narrator talks about Jack fading or vanishing, or being less than he once was. A sampling:

Although he looked drained and weak, he was making an effort to keep his eyes open.

I was glad to be there, watching Jack, his legs were much thinner than I remembered, and his chest seemed to have sunken in,

Then in the paragraph quoted in your question:

and although I never completely gave up, somehow I understood Jack’s reluctance or his stubbornness, the luminous, fresh, honey-slow silence surrounding him and his few words, as if his tall thin figure were vanishing, and all of California along with it;

Later towards the end of the story:

And the detective says, It’s all right, don’t worry, take your time, Madame Silvestri, at least you remember him, even that is useful, now I know for sure he’s not a ghost. And I’m tempted to tell him that we are all ghosts, that all of us have gone too soon into the world of ghost movies,

So my interpretation is that the mention of solidification is a contrast to the other descriptions of Jack: although Jack in general is fading away, his actual departure from Joanna's life is a solidification, a firming up of Jack's life even though Joanna isn't a part of it anymore.

EDIT: removed one of the examples because it's about a different character, not about Jack