Is mixing a catechol developer too dangerous for someone untrained in chemistry?

I'm interested in trying Hypercat at some point. I asked my AI chatbot about handling catechol, and it basically warned me not to try it, specifically without a fume hood. (I don't know if a typical community darkroom would have a fume hood).

If I wear protective equipment, mask, and gloves, I presume inhalation is the main risk? How would I minimize fumes? I've heard of people immersing bags of dry chemicals before tearing them open underwater to minimize risk. But I would have to measure out the appropriate mass of catechol from a plastic container, as far as I can tell. And here's a real non-chemist question: can you mix developer outdoors, with a fan plugged in, to maximize air circulation, if you don't have a fume hood?

How does the danger of mixing one's own catechol developer compare to mixing a working solution of a commercial developer? Photo Formulary's Precysol comes fairly concentrated: you mix Parts A and B at 5mL each per 500 mL of working solution. I always used gloves and goggles when mixing it. Do the gloves need to be stronger than ordinary disposable gloves? I can't remember if I wore a mask though. What is the fume risk of mixing such a working solution? The included instructions didn't highlight any risks beyond those of using any photographic chemistry; just the usual "All chemicals are dangerous and must be treated with respect" that comes with all their developers, tanning or not.

Thank you for your advice.

It's poisonous and a severe irritant, but you can mix most photo chemicals outdoors safely - or in a well-ventilated darkroom.

Use gloves when mixing (and a mask) or using it -- but you should use it with good ventilation (whatever that means).

Others will say, "Don't worry about it", but it's your call. A lot depends on how often you will use it.

ame01999 said:

I asked my AI chatbot about handling catechol, and it basically warned me not to try it, specifically without a fume hood.

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Looking at the formula, I'd say your chatbot is full of crap.

Mix it and try it. Just don't drink any of it.

You should take safety advice from something like a MSDS, not a chatbot. For example, here's a MSDS for pyrocatechol (easily found by googling): https://www.sigmaaldrich.com/US/en/...krFzadGjjEvm52GPz7aK4YyAFQjOmpq0FHXXOlcc-ImEn

Of course, it's also not trivial to interpret an MSDS. I don't have any experience with catechol and in general don't use the more exotic photo chemicals, but my read of that MSDS is I would use a mask, gloves, and eye protection, and preferably mix it outside. The protection afforded by nitrile gloves is quantified in the MSDS.

I hope I don't need to say this, but if you do mix it inside or outside and set up a fan, for God's sake don't have the fan blowing onto the material or mixing work surface. A fume hood is an exhaust hood. I would rather just work with powder (I am not sure if you are measuring out powder or liquid) outside without a fan, than have a fan blowing even if the fan is blowing away from the work surface. Blowing that stuff around won't do anyone any favors.

I failed grade 12 chemistry.
I've been mixing pyro developers since the 90's, and Pyrocat-HD since 2003. I work with a ceiling fan, with a dryer hose hanging down, and wear a respirator with the proper filter. I wear gloves if sheet film developing in trays (normally I use BTZS tubes). No worries.

I don't have a strong chemistry background, just a few college courses in the 60s. I have mixed a few catechol formulas, mostly MCM 100. I followed the guidelines recommended from Photographers Formulary. My converted bathroom darkroom has a celling fan over the sink vented to the outside, I leave door open and crack a window open in the bedroom so I have air flow from the outside up though the fan. I wear a good mask, wear rubber gloves and apron. MCM 100 also uses p-Phenylenediamine which is also toxic. Once in solution when using it I wear gloves, mask and an apron. I have not suffered any ill effects. Here is a link to the directions from PF for MCM 100.

Andrew O'Neill said:

I failed grade 12 chemistry.

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Was that because you spent too much time hanging around all your artist type friends?
After all, doing that could never lead to getting a good job, could it?

Catechol (pyrocatechin) is toxic, but not as toxic as pyrogallol. Simply mix in a ventilated area with normal protective equipment - gloves and a mask. I mixed Pyrocat-HD in glycol a year and a half ago (no error) - still using it and it's as good as new. Works great! Mix enough without worrying about its shelf life - at these dilutions, you won't need to handle catechol often!

ame01999 said:

I asked my AI chatbot about handling catechol, and it basically warned me not to try it, specifically without a fume hood.

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Well, there's the 'utility' of AI for you.

You've done the right thing in setting AI aside and come here to ask for advice.

As pointed out by several above, pyrocatechol/catechol is toxic and an irritant. However, it does not offgas significantly; i.e. at room temperature, there are no vapors etc. There's a faint phenolic smell, but that's faint compared to standing next to a tarred piece of wood on a summer's day. It would probably be be unhealthy to live in that smell 24/7 for an extended period of time. Being exposed to it for the few minutes it takes to mix a developer is perfectly harmless. So the AI-advice of a fume hood is pretty ridiculous and a good illustration of how AI 'says' things without having a concept of the content (it just puts word in a human-logical order and calls it good - regardless if those words make any sense).

Given catechol's toxicity, there are basically two safety concerns:
1: Dust
2: Contact exposure

Concerning (1) dust: catechol is generally sold in the form of flakes (as opposed to pyrogallol, which in my experience comes as a powder). These flaks don't kick up a lot of dust (or any at all). Evidently, don't shake the bottle with the dry catechol and then stick your nose into it after opening it.

The potential exposure is limited to the period you're in the vicinity of some uncovered catechol (for weighing it out). Handle it gently. That's really all it takes. Your exposure to any dust ends as soon as the catechol hits the liquid it'll be dissolved in.

Concerning (2): contact exposure occurs when you get the dry flakes or a solution containing catechol on your skin. Evidently keep it away from any mucous membranes or sensitive tissues (eyes, nose etc.) I never feel the need to wear a mask or goggles when handling catechol because I know I'm not clumsy enough to splatter developer all over the place. If you are somewhat clumsy or very concerned about your safety, a mask and goggles are a perfectly sensible idea.

It's easy enough to get something on your hands; it's a good idea to wear nitrile gloves. Nitrile is better than latex/rubber because the latter is permeable to some substances. Nitrile is generally also more comfortable and the gloves are generally easier to re-use. If you intend to re-use your nitrile gloves, wash your gloved hands thoroughly before taking off your gloves, so you don't create a point for skin contact when putting on some used, contaminated gloves (it's a minor risk, particularly in the catechol case, but still).

When using a catechol-based developer, there are no fumes, dust etc. As said, don't splatter it about. If you're the clumsy kind, wear gloves, mask, goggles as you see fit.

Furthermore, for photographic purposes in a home darkroom setting, the amount of catechol you'll handle is pretty small. Your purchase of catechol will likely be a pound or less. Your exposure to the dry material will be limited to the few minutes it takes to weigh out the small quantity you need for a batch of developer. These factors inherently limit your overall exposure - provided you don't do something monumentally stupid, like pick up a fallen flake of catechol with bare hands and then use the same fingers to wipe your itchy eye etc. Again, if you're the clumsy or thoughtless kind, protective apparel will catch most of these slips.

Overall, it's commendable that you're concerned with the safety aspects of darkroom work. Keep an eye on those aspects and decide on appropriate protective measures when you work with chemistry (dry or liquid). At the same time, there's no reason to be overly concerned or to panic about it, or to go overboard with draconian measures. E.g. a fume hood for a home darkroom is really not necessary. Decent ventilation is always a good idea - as in any space you spend considerable time in!

reddesert said:

for God's sake don't have the fan blowing onto the material or mixing work surface

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Thanks for pointing that out. I see some comments about ventilation and fans in this thread and your remarks are to the point and sensible. Ventilation in principle is good. Anything that kicks up and carries dust all across the room is NOT a good idea (although for handling a small jar with catechol flakes it's not going to do any harm either).

MattKing said:

Was that because you spent too much time hanging around all your artist type friends?
After all, doing that could never lead to getting a good job, could it?

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I got an B in grade 11 chem.

As with most chemicals, adhering to common sense and general safety practices will serve you well. I've been mixing Pyrocat-HD for over 20 years and, among the various pyro formulas, I find this one to be the easiest and, perhaps, safest to mix. I do wear nitrile gloves when mixing, but don't wear a respirator. I use a teaspoon to reach into the catechol container and slowly place it in a tray on the scale. Of the pyro chemicals, catechol seems to have the least residual dust but I work carefully, anyway.

I should mention that I do wear a respirator when handling pyrogallol. I find this chemical can introduce airborne dust, even when trying to work as careful as possible.

As a side note... Pyro stains everything in comes in contact with. If you're working on a counter top, for example, make sure to put something down to catch any drips or other "fumble finger" things that might happen.

Good luck and have fun!

Catechol is present in apples & bannanas. https://www.scienceprofonline.org/cell-biology/enzyme-exercise-catecholase-browning-apples.html

Developing agents are present in plants - you can make developers from coffee beans, the contents of the spice cupboard and plant galls.

As the old adage goes: "It's the dose that makes the poison." Eat a tablespoon of catechol, not a good idea. Carefully mix a few grams into water, no problem - the few micrograms that may fly up your nose will be less than what is in the apple you just ate. FWIW, Sigma Aldrich gives the LD-50 Rat as 300mg/kg - extrapolated that's about 20gm for a 150lb person.

Humans like to magnify insignificant risks - it seems to allow them to ignore the significant ones. It's not a bad thing - there are many risks we can do sod-all about, so why dwell on them?

Buy pre-mixed liquid concentrates of Pyrocat or whatever and just don't mix it yourself if you aren't confident you can deal with it.

Doremus

Nicholas Lindan said:

Humans like to magnify insignificant risks - it seems to allow them to ignore the significant ones. It's not a bad thing - there are many risks we can do sod-all about, so why dwell on them?

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Both valid points - somewhat sobering, but certainly true.

I have a somewhat different opinion about risk assesment. It is true that modern people obsess over certain risks to the exclusion of others (people obsess over food hazards, but you are way more likely to be harmed by a car than by something in your diet, etc). But, humans are also not good at estimating low-probability high-consequence risks. We tend to have an internal model of risks, like "I've done this several or many times and haven't come close to getting hurt, so it's okay." This is sometimes called a heuristic trap, similar concepts exist in avalanche safety, aviation, etc. The problem is that if something has say a 2% chance of serious harm, and you've done it 10 times with no consequences, you don't actually have enough information to rule out an unacceptable risk.

In the case of catechol, while its LD50 is higher than anyone could reasonably intake - and its LD50 is only about 20% higher than hydroquinone - LD50 is a poor measure of hazards, because there are often negative consequences well short of a lethal dose. Two things that were specifically called out in the MSDS were eye damage and ease of skin absorption. Those are easy to deal with, wear gloves and glasses. But you have to apply a model of risk assessment (safeguard against known hazards) rather than the "We did this twice last year and nothing bad happened" heuristic.

Skin absorbtion in substituted phenols (catechol, pyrogalol, hydroquinone...) is an interesting topic. Hydroquinone is a good example:

8% Hydroquinone skin lightening cream: https://www.mattebeauty.co/product-page/hydroquinone-cream-usp-8-skin-bleaching-cream

When vanity is in the driving seat all the MSDS statistics in the world don't count a good damn.

I offered to make up a bucket of HQ cream for my sister. Hers was 10%, prescription only, $100 for 2oz, plus another hundred for the Doc.. "Hey, I got a pound of this HQ stuff!" I told her. I was rebuffed.

It's not a case of "I mixed some up last summer and nothing happened" but of quantifiable risks that are zero, and not zero in the case of "1% of the time this will get you," but of "zero percent of the time." If you stay very far away from LD50 - you are safe.

There is a famous MSDS for water - "In case of contact flush with plenty of water." Interestingly, the same MSDS states there is no inhalation hazard - it seems you can inhale as much water as you wish.

reddesert said:

I have a somewhat different opinion about risk assesment. It is true that modern people obsess over certain risks to the exclusion of others (people obsess over food hazards, but you are way more likely to be harmed by a car than by something in your diet, etc). But, humans are also not good at estimating low-probability high-consequence risks. We tend to have an internal model of risks, like "I've done this several or many times and haven't come close to getting hurt, so it's okay." This is sometimes called a heuristic trap, similar concepts exist in avalanche safety, aviation, etc. The problem is that if something has say a 2% chance of serious harm, and you've done it 10 times with no consequences, you don't actually have enough information to rule out an unacceptable risk.

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This reminds me SO much of comments between my son and me many years ago. He would say, "Dad, what's the chances of xx (fill in the blank) happening?" My retort back was always, "Well, I guess if it happens to you it was 100%!"

Nicholas Lindan said:

If you stay very far away from LD50 - you are safe.

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Speaking of acute toxicity, yes. There are of course other modes of harm, which necessitate reducing exposure to the bare minimum (or avoiding it at all). In the case of catechol, think of concerns w.r.t. irritation and skin sensitization and suspicions of genotoxicity.

I find the best way to mix developers using, for example, catechol, is to have a well arranged work space and I do it when nobody else is at home, to minimize unexpected interruptions. As Koraks said, catechol is not dusty, so just work patiently, neatly and methodically and you won't have a problem.

Knowing what you are doing and being fully aware of the risks and safety protocols helps a lot. If you aren't in that place yet, learn how before mixing toxic chemicals.

Doremus