Anon Ymous brought up an interesting question: which danger is marciofs most concerned about? Is it the toxicity of the process liquids? Or is it toxic fumes emanating from these liquids? Is it maybe storage of hazardous precursor materials? Is it safe disposal of waste chems? Depending on to which extent you can address either of these hazards, there will be very different answers.
To give you an example: in terms of process liquids and storage,hypo alum toner is very benign, but not everyone is capable of safely operating a heated bath at 50°C/120°F in their darkroom (think electrical hazards, failed temperature control leading to fire hazards and toxic smoke, ...). Depending on circumstances hypo alum toner may be the most benign, or the most hazardous toner to use.
I would think iron blue toner would be safe, but IDK how archival it is. This is assuming a "standard" method of toning using one of the commercial brands?
You can also tone prints in food coloring, coffee, tea, etc.
Tea?
Hypo alum sepia toner must be the most benign. Apart from that, sepia toners based on sodium sulfide are a bit more dangerous, although good ventilation eliminates any problems. Those based on thiourea are considerably more dangerous.
All of them are ok if handled appropriately.
Two interesting points about selenium. Selenium is toxic in large amounts. However it is also an essential trace mineral in the human diet necessary for proper cell function. It can be found in many vitamin and mineral supplements. When taken in large amounts it is excreted in the breath and sweat as obnoxious smelling dimethyl selenide. The smell is described by some as that of rotting horseradish.
In the early part of the last century tellurium, a chemical cousin of selenium, was also used as a toner. Its toxicity is similar to that of selenium. However the organo-tellurium compounds produced in the body are far worse smelling than those of selenium. Miners who worked silver or gold mines often developed tellurium breath. This was said to wilt daisies and stupefy small animals at 50 paces.![]()
What is LD50 oral for selenium toner either stock or 1:10 diluted? The concentration of sodium selenite listed is usually 1-5%
Interesting. In what ways specifically are those based on thiourea more dangerous than sodium sulfide. I had always thought that Tim Rudman, an expert on toners had said that thiourea was easier on the lungs and overall less dangerous than sulfide tonersHypo alum sepia toner must be the most benign. Apart from that, sepia toners based on sodium sulfide are a bit more dangerous, although good ventilation eliminates any problems. Those based on thiourea are considerably more dangerous. Selenium toners aren't benign either.
All of them are ok if handled appropriately.
Thanks
pentaxuser
Finally, by the same token, breaking wind may also be very, very dangerous, as hydrogen sulfide is one of the smelly components in flatus.![]()
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