About

geometricblackness.org is an open-research notebook about one idea: a thing can be black because of its shape, not its material.

A surface folded into the right geometry — V-grooves, cavities, pyramids — traps light by bouncing it until almost none escapes. Razor blades, vinyl records, black-silicon solar cells, a moth's eye, and a folded-metal rooftop absorber all do it, at scales five orders of magnitude apart. We test how well it works, publish the numbers, and hand you everything you need to check us.

Who's behind it

We're 601 Delaware — a 1932 industrial building in San Antonio, Texas, being brought back as a working coffee roastery and an industrial nonprofit: a real factory that does its own applied research and publishes openly. The building has to produce and teach. Geometric blackness is one of the problems the building actually needs solved — we want to cool a hot Texas factory with solar heat instead of grid electricity, and that runs through a good absorber surface — so the research isn't academic. It's a line item that happens to be beautiful.

Why we publish openly

Most applied R&D is kept quiet until it's a product. We do the opposite, for three reasons:

It's checkable. A finding you can't reproduce isn't a finding. Our first proof costs about $65 and one sunny afternoon; the protocols and parts lists are here so you can run it yourself and tell us if we're wrong.
The negatives are the value. We publish what doesn't work as plainly as what does — the vinyl record that warps in the sun, the geometry that helps a shiny surface far more than a black one, the hot-afternoon performance we lose. Honest failure is most of the signal.
It's the right thing for an industrial nonprofit to do. If a cheap fold can replace an expensive coating, that belongs to everyone who restores buildings, builds collectors, or just likes black things. We're not patenting a shape.

What you'll find here

Findings & data — reflectance and thermal measurements, raw, with the conditions they were taken under.
Replication kits — step-by-step protocols and procurement lists, from the $65 afternoon proof up to the full efficiency-curve rig.
Explainers — the lineage from razor blade to rooftop, and why geometric blackness works at all.
The Fuller thread — Buckminster Fuller wrote the light-trapping mechanism into Synergetics in 1975 and predicted the optimal geometry. We're testing whether he was right. We'll show our work either way.

What we're not yet measuring — the open physics

We're publishing this gap on purpose, because it's the part most likely to sink the thesis. Measuring how black a surface is and measuring whether it makes a better solar collector are not the same experiment — and so far we've mostly done the first.

The emittance penalty. A cavity that traps incoming sunlight also traps and re-radiates its own heat. By Kirchhoff's law, a better absorber at a given geometry is a better emitter at that geometry — geometric blackening raises absorptance and thermal emittance together. That's the link an expensive selective coating is built to break, and the link a fold cannot. We measure reflectance; we don't yet measure the hemispherical thermal-IR emittance that decides the loss.
Blackness is the wrong score. The number that matters is collector efficiency at the temperature an adsorption chiller actually wants (~70–90 °C), not absorptance at room temperature. At operating heat, radiative and convective losses dominate — and geometry makes the radiative loss worse. The efficiency curve, not the blackness, is the real result.
The roof sets the aperture. Folding multiplies surface area but not the area facing the sun. Each photon gets more bounces; you don't catch more photons per square meter of roof. For a surface that's already ~90% black, the headroom from trapping is only the last ~10%.
Blackness is angle-dependent. A V-groove traps best for light entering near head-on — which is how the razor-blade blackbody is measured. A rooftop watches the sun cross the sky, so normal-incidence reflectance flatters the day-averaged number.
Two different tricks wear the same name. Millimeter folds trap light by bouncing it — geometric optics, wavelength-blind, and so they raise IR emission too. A moth's eye and black silicon do something else entirely: sub-wavelength texture that cancels reflection by impedance matching. Only the second kind can be black to sunlight without also being a good radiator — and our rooftop sawtooth is the first kind.
The chiller wants temperature, not just heat. An adsorption cycle needs heat above a threshold; below it the cooling collapses. A blacker-but-leakier absorber can deliver more low-grade watts and less usable cooling. More heat is not the goal — enough temperature is.
The surface isn't the system. Real high-temperature collectors wrap the absorber in glazing, an IR-reflective cover, and convection suppression. Folds also add area for convection and dust-collecting valleys. Optimizing one bare surface skips most of the heat balance.

So here's the test that settles it: hold a grooved sample and a flat sample of the same metal at the same useful operating temperature, in the same sun, and measure the net heat each delivers — plus the thermal-IR emittance of each. If the groove's absorptance gain survives its emittance and convection penalty at 80 °C, geometric blackness earns its place in the collector. If it only wins near room temperature, then it's a fine cheap absorber for low-grade heat and not a coating-killer for chiller-grade heat. Either answer is worth publishing.

How to take part

Build the afternoon test and send us your numbers — confirmations and contradictions. Replicate a result, improve a protocol, point out an error in the physics. This is a notebook kept in the open, not a finished paper; it gets better when more people fold metal and hold it up to the sun.

A shape can be black. Help us find out how black.

License

All text, data, and protocols on geometricblackness.org are licensed CC BY 4.0. Reuse, remix, build on, and redistribute any of it — including the methods and parts lists — for any purpose, including commercially. Just credit geometricblackness.org / 601 Delaware. We're not patenting a shape.