Negative Processing Chemistry Research

Some links to lower-toxicity recipes for dev/stop/fix, with some price and source exploration:
Chems
Dev
Ascorbic Acid (vitamin C)
225g - $13 - ebay - $0.057/g
1000g - $40 - ebay - $0.040/g
500g - $23 - ebay - $0.046/g
450g - $35 - ebay - $0.077/g
225g - $17 - ebay - $0.075/g
450g - $20 - ebay - $0.044/g
900g - $30 - ebay - $0.033/g
Sodium Carbonate (Soda Ash)
500g - $40 - ebay - $0.080/g
680g - $37 - ebay - $0.054/g
1000g - $30 - ebay - $0.030/g
100g - $5 - ebay - $0.050/g
500g - $12 - ebay - $0.024/g
Stop
As the developer isn't as aggressive, we can get away with water bath for stop.
Fix (non-hardening)
Sodium thiosulfate (pentahydrate/crystalline)
400g - $37 - etsy - $0.0925/g
113g - $7 - ebay - 113g – $0.0619/g
2500g - $50 - ebay - $0.0200/g
1360g - $55 - ebay - $0.0404/g
1360g - $50 - ebay - $0.0368/g
450g - $15 - ebay - $0.0333/g
Sodium sulfite (anhydrous) - Increases shelf-life of fix, not necessary
30g - $40 - ebay - $1.33/g
500g - $150 - ebay - $0.30/g
500g - $50 - ebay - $0.10/g
450g - $30 - ebay - $0.07/g
450g - $23 - ebay - $0.05/g
225g - $16 - ebay - $0.07/g
450g - $14 - ebay - $0.03/g
100g - $10 - ebay - $0.10/g
Articles
https://petapixel.com/caffenol-developing-film-with-coffee/
https://www.35mmc.com/18/08/2020/polyphenol-developer-alternatives-a-world-full-of-options-by-daniel-keating/
Possibly with espresso given that we have coffee roasting and an espresso machine?
Personal Safety Risks
These chemicals have been selected for general low-toxicity, but risks and appropriate precautions exist.
Chemical
Risks
Precautions
Sodium carbonate (soda ash)
Alkaline irritant. Pure dust can irritate nose, throat and eyes.
Working-strength solution (~2.7%, pH ~11) can dry or irritate skin on prolonged contact.
Eye contact with powder or strong solution is main issue.
Gloves & eye protection appropriate for when scooping or pouring.
If not gloved during mix, wash hands immediately afterwards.
Rinse eyes with water for 15 min if splashed.
Ascorbic acid
Very low. Mild irritant as a dust.
Avoid raising/breathing dust.
Coffee
Effectively none.
Sodium thiosulfate
Very low toxicity. Mild skin and eye irritant, and prolonged skin contact dries skin.
Gloves.
Rinse eyes with water for 15 min if splashed.