Details in the process of making 'blacker than vantablack' coatings (part 1?)

Recreating MIT's "blacker than vantablack" in a home shop (almost).

MIT press release:
MIT nanotube-on-aluminum paper:

NIST nanotube darkness comparison:

Shaper handheld CNC router:

Almost-as-large quartz tube (I used 76mm OD) :

Insulating firebrick for tube furnace:

Black velvet on Amazon:

LR-1 spectrometer:

Applied Science on Patreon:

(part