[peterburkimsher]

Thank you trop for the links!

Do you know if there's a database of natural chemicals for filters?

Specifically, I'm looking for a 0.3 µm ultraviolet filter (or any base-2 harmonic e.g. 2 * 0.3 = 0.6µm, 4x, 8x, 16x).

Tangentially related, I'm also searching for any flowers whose pollen grains are 19.2 µm (0.3 µm * 64).

As you say, the 19th-century (and Ancient Greek, Chinese, Egyptian, IVC) experts knew well about the biological solutions for technical questions. I just have no idea where to learn about natural substances.

[trop]

peterburkmisher: I wish I knew! I've been wondering about all this myself, and where even this knowledge lies these days. Materials scientists? Chemists? It sees a question too specialized for the former, and not specialized enough for the latter? Please anyone who knows...?

More generally:

Josef Maria Eder's "History of Photography" [1] is a semi-technical survey of 19th and early 20th century processes. Part of what it makes it wonderful is the narratives of so many chemist/photographers trying to get their discoveries supported by scientific societies and/or the market, with vastly varying success. As Eder was actually there doing the work[2], he has much to recount.

Much more recent, Richard Benson's "The Printed Picture"[3] takes on how images have made their way to paper. Benson probably knew as much about this as anyone still alive.[4] If in Philadelphia, it's possible still to catch an exhibition of his work.[5]

[1] https://archive.org/details/EderHistoryPhotography

[2] https://www.metmuseum.org/art/collection/search/296322 is a beautiful example

[3] http://www.worldcat.org/oclc/495363201

[4] https://printedpicture.artgallery.yale.edu/color-photography

[5] https://philamuseum.org/calendar/exhibition/richard-benson-w...

[peterburkimsher]

Thank you for more links to read around the subject!

In case you're wondering why 0.3 µm is so important, this is why:

https://www.visualcapitalist.com/visualizing-relative-size-o...

Hypothesis 1 is that there is a correlation between particle size and wavelength of resonant light.

Hypothesis 2 is that there is a correlation between other wavelengths of light and mutations.

corollary to that: masks = COVID concentrators, left as litter on the street, under broad-spectrum sunlight, will be disinfected, but also occasionally mutated.

Therefore mask litter is a very high risk.

Therefore all humans must pick up masks from the street, dispose of them safely, and wash hands immediately. Love your neighbour, take the risk because you're vaccinated. And keep wearing that mask, even though it's < 100% efficient, it's better than nothing because it cycles.