Question about safety and bichromate fumes

Hi! I am looking for advices on working safely with more toxic chemicals in a darkroom at home. More specificaly I am concerned with bichromate fumes in a poorly ventilated room. I am now just in the reading and researching phase and am very new to this. I did follow a small course for some processes (cyanotype, kalitype...). The future darkroom has no ventilation. I does have a window but then again I am located in Montreal and part of the year it is not so convenient to have it wide open (especially when it gets down to -25C/-15F). Maybe an inline duct fan would be a good solution? I could possibly connect it to a black painted acrylic panel that would be fixed in the window when using it. I think the skin and eyes contact issues I know how to handle but it's the fumes and powder that really concern me.

Thanks for any inputs and advices!

Hey there,

I used potassium dichromate for years in a basement with minimal ventilation when I used to make gum prints. I'm not sure exactly what you're using it it for, but unless you're igniting it in some way it shouldn't be emitting any sort of fumes at all when used normally. When people recommend using ventilation, their main concern is breathing in the dust. I'd recommend weighing out and mixing the stuff outside while wearing a dust mask. Once it's in solution, it should be fairly safe to work with, as long as you're sensible. Just avoid skin contact (wear gloves, goggles, maybe an apron). With my dichromate solutions, the bottle never leaves the sink, so that any potential spills are easy to clean.

Ventilation is important even if you are using incredibly benign chemicals. So I would recommend you improve the ventilation, and then use the bichromates carefully.

If a substance does not emit any fumes, there does not need to be special ventilation.

ThePhotoChemist said:

Hey there,

I used potassium dichromate for years in a basement with minimal ventilation when I used to make gum prints. I'm not sure exactly what you're using it it for, but unless you're igniting it in some way it shouldn't be emitting any sort of fumes at all when used normally. When people recommend using ventilation, their main concern is breathing in the dust. I'd recommend weighing out and mixing the stuff outside while wearing a dust mask. Once it's in solution, it should be fairly safe to work with, as long as you're sensible. Just avoid skin contact (wear gloves, goggles, maybe an apron). With my dichromate solutions, the bottle never leaves the sink, so that any potential spills are easy to clean.

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That's pretty much what I do. Once it's dissolved in water, the airborne risk is gone.

The MSDS sheets for Potassium or Sodium Bichromate is quite alarmist, I was responsible for drawing up the COSSH assessment for a lab I ran and we used far worse chemicals. Sensible precautions, definitely no ingestion, wear gloves, never heard of or seen fumes.

Ian

The only danger, which came close to "fumes of dichromate" is the production of airborne aerosols and that is the case if you use a spray bottle for applying a solution of dichromate, which in case of gum printing is not necessary. Okay dust can be a hazard, too but only if you prepare your solution.

bj68

I don't know if you need to heat the solutions. In that case there would be some potential for producing small amounts of aerosols. Otherwise there aren't fumes because it is a solid.

What you want to take care of its to not have drops of your solution go anywhere you don't know and hence won't clean away, especially the floor. When they dry they'll leave residue which will become dust when not wiped up. Ventilation will not necessarily protect you from dust exposure. Unless everything happens inside a fume cupboard.

lantau said:

I don't know if you need to heat the solutions. In that case there would be some potential for producing small amounts of aerosols.

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How??
Unless you boil the solution.

I actually heat my potassium dichromate. I use a super saturated solution which means I have to heat it up to about 120 degrees Fahrenheit to hold the crystals in suspension. I have to reheat the bottle every time before I use it, as crystals will reform at room temperature. Still, I do that in a microwave to contain any possible fumes (which I've never noticed any) and mostly for convenience. I suppose there could be a health hazard issue, if one were so inclined to do something stupid, but in the real world, it's not an issue. Only a small amount of the solution reaches boiling, and only for a brief second or two, and most of it either diffuses or condenses by the time I've opened up the microwave.

Thanks everyone for those useful answers. It's quite reassuring to think it can be handled safely with care in normal conditions. I will try to improve ventilation anyway and will wear a mask, googles, and apron if I am ever to make my own solution (and do it outdoor).
What chemicals used in alternative/historical processes (or film or silver print) would be more problematic when it comes to fumes and ventilation? Solutions containing formalin (such as some used for developping color film)? What else?

Photopathe said:

...
What chemicals used in alternative/historical processes (or film or silver print) would be more problematic when it comes to fumes and ventilation?

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The history of photography has some real doozies. Hot mercury vapor to develop daguerrotypes, potassium cyanide used in concoctions that also contain strong acids, ether, glacial acetic acid, elemental iodine, powerful ammonia ( sometimes mixed with silver salts ), fluorine compounds, sulfide compounds, uranium toners, elemental selenium powder.... the list goes on and on. Lots of things that are probably best left alone!

You are less likely to find the worst of these things in modern versions of historical processes, but if you start exploring historical/alt processes, it's a must to learn about everything you are using. I usually look at the MSDS, read a lot, look up vapor pressure ( if you look up vapor pressure for sodium or potassium dichromate, you'll find that it is negligible - at room temperature ). Since I'm not a chemist, if there's anything I'm uncertain about, I ask questions here directed to people who know what they are talking about. And if you use something dangerous, you also need to think about proper storage and disposal. I enjoy reading the journals from the early days of photography, but there are quite a few ingredients that I leave out and wouldn't even have at my house. Sometimes there are safer alternatives ( a couple drops of tincture of iodine from the drugstore works just as well as a few grains of elemental iodine ) and sometimes it's better just to skip it.

Wet plate collodion would need adequate ventilation. Cyanotype and Van Dyke don't really, but the fixer in Van dyke can be unpleasant to smell for some, but not dangerous. Casein is similar to gum bichromate, but adds amonia which is also unpleasant to smell. That's all I have experience with.

And I wouldn't mix the dichromate solution outside, due to wind, unless you can work in an area without any wind. You don't want the wind to kick that stuff up into the air where you breathe or get it in your eyes. I mix mine in the kitchen, but am meticulous about not letting any dichromate touch anything where food is prepared. It's a large room with plenty of light and space and a sink with running water and paper towels handy in case of an accident.