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C. D. Keth
1-Sep-2012, 20:34
I'm interested in learning to make daguerreotypes and I'm starting with safety in mind. I understand that breathing any of the chemicals involved would be pretty bad for your health.

Has anybody made a portable fume hood for this purpose?

Here's what I was thinking: something like a bathroom vent fan built into a briefcase-size hood that can be set up on legs like a little table and enclosed with tent fabric. For outdoor use, it would just have a little chimney that directs fumes away from me. For indoor use, I would vent it out a window with dryer vent hose.

Jason Greenberg Motamedi
1-Sep-2012, 20:59
Tell me more about what you plan on doing.

If you are using iodine only (Becquerel development) in a tight fuming box, then what you describe is a temporary solution, but not ideal. Your iodine will eventually corrode your vent. If you are planning on the traditional method, using iodine, bromine and mercury, then what you describe is no where near enough, and you will slowly kill yourself and possibly others. Bromine is very corrosive to metal, and will destroy the little vent fan in a few months. Mercury attacks aluminum, and will also probably kill your vent. One thing to think about is that bathroom vents are designed to carry off hot steam. Both bromine and mercury vapors are heavier than air, so a top-vent only will not work well. Look at the design of lab hoods, and you will see that they have baffles which pull air from the bottom, middle and top of the hood, ensuring that all fumes and vapors are drawn away from the opening. In addition, a bathroom vent will not have enough draw to pull air from the opening of a decently sized box, which you will need for two fuming boxes and a mercury pot.

C. D. Keth
1-Sep-2012, 21:21
Tell me more about what you plan on doing.

My preference is to get into practicing the traditional mercury developed, iodine and bromine sensitized process. This is exactly why I am investigating the safety before I go about doing anything else. I've found a lot of information on the process itself but surprisingly little on modern safety practices that apply.

It sounds like a proper lab vent hood is really the only thing to do. Does that sound right? I was trying to avoid that because of the huge expense but safety isn't optional.

Jason Greenberg Motamedi
1-Sep-2012, 21:43
There is quite a bit on modern safety methods, but not here. Start with Ken Nelson's article on Mercury (http://www.cdags.org/wp-content/uploads/Merc.Mod.Dagist.pdf), and then consider that the bromine is actually much more dangerous than the mercury, and is one of the most corrosive, toxic and spill prone substances in existence. Can I suggest taking a workshop? Doing it yourself is the least cost-efficient and most dangerous way of starting. Even a Becquerel workshop will get you started so you can prepare your own plates, and learn the basics of polishing. And yes, you need a real fume hood, and have to understand enough about the chemicals you are working with to ensure that the hood is properly vented.

C. D. Keth
1-Sep-2012, 21:50
Thank you for the reading and other recommendations. This is exactly why I start reading and asking questions long before I lift a finger to do something like that. Can you recommend a particular workshop that you feel is particularly good, or perhaps one that is reasonably close to Southern California?


There is quite a bit on modern safety methods, but not here. Start with Ken Nelson's article on Mercury (http://www.cdags.org/wp-content/uploads/Merc.Mod.Dagist.pdf), and then consider that the bromine is actually much more dangerous than the mercury. Can I suggest taking a workshop? Doing it yourself is the least cost-efficient and most dangerous way of starting. Even a Becquerel workshop will get you started so you can prepare your own plates, and learn the basics of polishing. And yes, you need a real fume hood, and have to understand enough about the chemicals you are working with to ensure that the hood is properly vented.

Nathan Potter
1-Sep-2012, 21:56
Jason has some good suggestions above. For the chemistry you mention a fume hood or box type structure made from polypropylene sheet would not corrode. You can buy sheets of polypro of 3/8 inch thickness and fabricate a design. I have had a lot of such hoods made specially for corrosive chemistries. Polypro can be heat welded or more simply drilled and tapped then assembled using stainless steel machine screws. All takes a bit of skill and practice. This doesn't need to be a very sophisticated design.

For much heavier than air chemistry I have used a lip exhaust scheme as mentioned by Jason. Typically this is implemented by using a narrow slot fully across both the front and back of the hood structure. An exhaust line from the lip grabs the contaminated air and connects to the exhaust fan or blower which shoots the effluent to the outside at a safe distance. The exhaust blower needs to be resistant to the chemistry.
A corrosive chemically resistant blower is best to use (often with polypro parts) but I've seen people coat a standard blower with a protective coat of plastic to extend lifetime.

Maybe just a 2 X 2 X2 ft. box with front open for work access would suffice. A channel at both front and back would function as an adequate lip exhaust with exhaust tube running to a blower remote from the hood to avoid vibration. If I remember correctly it is most efficient to achieve about 100 cu ft. / min. / linear ft. of hood front opening. Thus you might be looking at 200 cu. ft. / min. for a 2 X 2 X 2 ft wide box. Often a vertically sliding front window is used to partially close off the front opening and to increase the velocity of room air into the hood.

Nate Potter, Austin TX.

Jason Greenberg Motamedi
1-Sep-2012, 22:10
I can't suggest a workshop in Southern California, but Eric Mertens teaches occasional workshops in Oakland. Ken Nelson and I taught a series of workshops last month in NY at CAP (Ken will teach another in the Spring, I won't teach again until the Fall of 2013). Jerry Spagnoli teaches Becquerel workshops all over the US, and Mike Robinson teaches from Toronto and perhaps elsewhere. Poke around at cdags.org to find more.

Nathan is correct, one can easily build a hood, but it takes knowledge and time, and you will need a box with a workspace of at least 4' lateral feet to fit all the boxes. I have built them out of acrylic, and even plywood. Both are "good enough" materials if there is enough air movement (and yes 100 ft/min is the minimum face velocity), but a mistake can be deadly. Of course, buying the wrong kind of fume hood (like a recirculating/filtering one) can be just as bad.

Dan Dozer
2-Sep-2012, 18:41
I'm not a wet plate person, but I do know a lot about chemical fume hoods. Please heed all the warnings that people are saying about using hazardous chemicals. When you're talking about making some sort of fume hood, you might take a look at this commercially manufactured chemical fume hood for ideas. I specify these on my projects quite frequently for use with small amounts chemicals use and you might get some ideas from it. Granted, it does have stainless steel in it and others have said to use polypropylene (which has overall better chemical resistance. Note the slotted back damper panel that takes fumes from all heights above the work surface. Also note the sloped clear plexiglass panel in front that covers your face from the fumes (this is real important).

http://www.labconco.com/product/protector-work-stations-without-blower/853