Triethanolamine

AcceleratorC6H15NO3CAS: 102-71-6Shelf life: 36 mo
Triethanolamine
Image: ChemSim — Public domain

Physical Properties

  • Molecular Weight: 149.19 g/mol
  • Solubility (20°C): 1000 g/L

Also known as: TEA, Trolamine, 2,2',2'-Nitrilotriethanol

Triethanolamine (C₆H₁₅NO₃, often abbreviated TEA; CAS 102-71-6) is a viscous organic liquid alkali used almost exclusively in photographic liquid developer concentrates.[1] Unlike the inorganic alkalis, TEA is itself a solvent — it holds developing agents in solution at concentrations where sodium- or potassium-carbonate formulas would precipitate. This property makes it the alkali of choice for the class of "water-free" or "propylene-glycol-based" developer concentrates popular in contemporary DIY photography chemistry.[2]

Photographic uses

  • Liquid concentrate developers: PC-TEA, Pyrocat-HD glycol variant, and several Anchell/Troop formulas use TEA as the alkali in an organic solvent (propylene glycol) base. The finished concentrate is shelf-stable for years as long as it stays dry and sealed.
  • Kodak Xtol (historical): Early Xtol variants used TEA contributions alongside sodium metaborate; current formulations emphasize metaborate.
  • Silver solvent effect: TEA has a mild silver-complexing action that contributes to fine-grain development — a secondary benefit beyond its role as an alkali.
  • pH modulator: TEA provides moderate, well-buffered alkalinity (working pH 10–11 depending on concentration), between carbonate and sodium metaborate in effective strength.

Practical notes

Supplied as a pale yellow viscous liquid. Absorbs moisture and carbon dioxide from the air, gradually converting to the less-active carbonate salt on prolonged exposure — store in a tightly sealed container under nitrogen or in the original supplier bottle with minimal headspace. TEA that has darkened noticeably to brown/amber has partially oxidized and is suitable for general use but not for precision-grain fine-developer work.

Used at 50–80 g/L in typical water-free concentrate formulas. The final working solution dilution (typically 1:15 from concentrate) gives the low working concentration where TEA's mild alkalinity is appropriate.

Related compounds

Diethanolamine (DEA) is a related amine alkali used in some older formulas; generally superseded by TEA because of DEA's carcinogen classification. Monoethanolamine (MEA) is the simpler ethanolamine with stronger alkalinity but more volatile chemistry. Sodium metaborate is the inorganic-solid alternative most similar in photographic effect.

Safety Notes

Acute hazards

Triethanolamine has low acute toxicity:

  • Mild skin and eye irritant: concentrated TEA causes transient redness on skin contact and mild stinging in the eye. Working-strength developer is essentially non-irritating.
  • Low inhalation risk: TEA is not volatile at room temperature; vapor exposure is not a meaningful concern in normal darkroom handling.
  • Harmful if ingested in quantity: a substantial swallow causes nausea and gastrointestinal upset.

Storage & handling

  • Personal protective equipment: Nitrile gloves and safety glasses for concentrated liquid handling; not required for working-strength developer dilutions.
  • Storage: Tightly sealed in a cool dry cabinet. Minimize headspace in partially-used bottles to slow air-driven degradation.

First aid

Consult the full Sigma-Aldrich Safety Data Sheet for authoritative first-aid instructions.[3] In brief:

  • Skin contact: Rinse with water.
  • Eye contact: Flush with running water for at least 10 minutes; seek medical attention if irritation persists.
  • Inhalation: Move to fresh air; unlikely to be relevant at darkroom concentrations.
  • Ingestion: Rinse mouth; seek medical attention for substantial swallow.

References

  1. BOOK Anchell, Steve; Troop, Bill. The Film Developing Cookbook 2nd ed. Routledge, 2019. ISBN 9781138959187. ↩
  2. BOOK Haist, Grant. Modern Photographic Processing, Volume 2 1st ed. John Wiley & Sons, 1979. ISBN 0-471-04635-X. ↩
  3. WEB Sigma-Aldrich (Merck KGaA). Sigma-Aldrich Safety Data Sheets Sigma-Aldrich. https://www.sigmaaldrich.com/US/en/search/safety-data-sheets ↩

Reference databases

Last reviewed 2026-04-21