Well, toxicity wise, you can drink a tablespoon full of Propylene Glycol and enjoy the sweet syrupy taste, but the same action with Ethylene Glycol will put you on a kidney dialysis machine (if you survive). This is an approximate scenario. Both are sweet tasting syrups that children and pets love to get into. It is usually fatal for children or pets to ingest any amount of Ethylene Glycol.
Good luck with the finger.
Those are really gorgeous results and a great graphic. I can hardly wait to see your findings written up at the end the discovery process. In the meantime, it's good to see the process in action. I'm going to post a link to this thread on The Light Farm. Folks who aren't APUG members will have to register to see the jpegs, but I doubt that will hurt Sean's feelings.
Originally Posted by tim_bessell
Sometimes it's hard to know how pointed and direct to be when writing about emulsions in this forum. I apparently didn't make my point well enough before. Let's talk 'perspective'.
Originally Posted by Photo Engineer
No one in their right mind would deliberately choose the more toxic of two equal chemicals, but unfortunately making your own photographic materials involves non-food ingredients. The one that gives me most pause is silver nitrate. A drop splashed into an eye could blind. Wouldn't want to be a blind photographer. Yet, one rarely sees strong cautionary statements in conversations about making salted paper, because the process is considered a basic, simple, 'newbie-to-alt' process.
I use Photo-Flo 600 because it works. My emulsions with 200 were impressive buckets of fail. As Ron well knows, I use many drops of undiluted 600 concentrate with my paper emulsions. I don't dilute it. On the other hand, I had to use so much 200 that I was throwing off my gelatin/water ratio. If I did need a fraction of a drop of 600, I would not try to dilute a drop. I would make a reasonable quantity of working solution. This is a technique that is required for emulsion making. Many chemical ingredients are only needed in fractions of a gram.
Two more points: 1) We're talking about paper emulsions in this thread. I don't use any of the Photo-flo's in my negative emulsions, dry plate or film. I use Everclear. It could also be used with papers. Vodka is a good substitute if you take the extra water in it from somewhere else in the recipe. Wouldn't advise drinking Everclear either, or too much Vodka for that matter.
2) Photo-Flo 600 has been discontinued by Kodak. Staying undogmatic about specific chemicals is essential for the continuance of the wet darkroom in general, and emulsion making in particular. Always, always, think about alternatives. Photo-Flo 600 is a combination of EG and Triton-X (9002-93-1). The latter is also marketed as Daniel Smith Acrylic Flow Releaser. Although I still have almost two gallons of Photo Flo 600 left (more than a lifetime's supply), I've been experimenting with acrylic flow releaser and it works great. But, even with acrylic painting, caution is in order. Basically, Daniel Smith says don't breathe it, don't drink it, don't wash your hands with it, don't use it as an eyewash. Good advice, even with the chemicals we clean our bathrooms with. And am I the only one worried about breathing the fumes that come off an inkjet printer? I keep my printers in a ventilated closet because otherwise I get a headache. Is the monitor I'm looking at right now going to give me brain cancer? Perspective.
I answered what I did in response to Ray's question. I gave the practical reason why. There is no substitute for Silver Nitrate and so that falls within my practical advice.
But, remember that I wore safety glasses and rubber gloves when working with the raw chemistry, and you saw the condition of my lab coat. I wore it on purpose to demonstrate the effect on clothing and skin.
I advise prudence in all things. I do not want newbies, their families or pets to be injured by incomplete or erronious posts that I make.
But, as I have said, "do what works for you". The caveat is that you will then be responsible for the consequences. EG is now no longer used in antifreeze. Years ago, it was and spills in garages and driveways attracted children, pets and wildlife due to its pleasant sugary taste. After many illnesses and deaths, it was banned for this purpose. I would be shirking my duty if I did not point this out.
And, if you would please note, I used almost exactly those words in your post to introduce my students in my workshops to Silver Nitrate. I try to err on the side of caution rather than give blanket ok to everything. And, I give appropriate warnings wherever possible.
Hello To All,
In working with Silver/Gelatin glass negatives I found that I COULD use Photo-Flow 200, as long as my emulsion was hardened, with Formalin,Glyoxal or Chrome Alum. No hardener---Emulsion sheets off the glass when PF 200 is used.
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Vodka? Could I use Beer/ Just about 20x more? I have been buying Denatured Reagent Grade Ethanol. But be carefull of what the denaturant is. I buy "Type 1", which is 4-5% methanol. As long as the denaturant is an alcohol, you shuold be OK. Avoid mixtures with rings.
Avoid mixtures that become cloudy when added to plain water. The denaturant is incompatible with emulsions for the most part.
Ray - good question. And a fairly complicated one.
Getting to the nitty-gritty, I personally rank ethanol, ethylene glycol, and propylene glycol all at about the same level of toxicity. Here's my reasoning behind that choice.
I've heard the same stories (and they are true stories) that PE is mentioning about ethylene glycol and propylene glycol. Ethylene glycol was used in the past as a food additive - I've heard stories of people drinking wine that had too much added as a sweetener having died from drinking it. And it is now banned in many countries from use as a food additive for that very reason. Many antifreeze manufacturers have also switched from ethylene glycol to propylene glycol formulations. All true.
We should try to follow best practices when handling chemicals or other materials, whether at home or at work, we would want to minimize our exposure to hazards whenever possible. It's really the smart thing to do. Keep in mind that hazards can be split into 3 different catagories, physical hazards like exposives or flammable materials, environmental hazards like bioaccumulation and aquatic toxicity, and health hazards as we are discussion here, which include oral toxicity, dermal, gaseous, vapours, and mists. With the use of ethylene glycol and propylene glycol we probably only really need to concern ourselves with the oral and dermal toxicity.
The overriding question is how can we determine what materials are hazardous, and based on that information, how do we best minimize our exposure to risk. MSDS sheets are helpful with this as they list many potential known hazards for chemicals and products and also many physical properties and even give suggestions for what is the proper personal protective equipent when handling these chemicals.
Looking at MSDS from respected sources as Fischer Scientific and JT Baker, you can see that they are rather similar.
Ethanol (absolute, with no denaturants in it) -
NFPA Health Rating: 2 Moderate
Oral rat LD50: 7060-9000 mg/kg
Skin LD50: not given
NFPA Health Rating: 2 Moderate
Oral rat LD50: 4700 mg/kg
Skin rabbit LD50: 9530 mg/kg
NFPA Health Rating: 2 Moderate
Oral LD50, rat: 20,000 mg/kg
Skin rabbit LD50: 20800 mg/kg
As you can see, Ethylene Glycol takes a dose half as much as absolute ethanol to reach the same LD50 result. Propylene glycol take a dose twice as large as absolute ethanol and 4 times as large as ethylene glycol.
It's similar for the skin LD50 - ethylene glycol is about twice as toxic as propylene glycol. (There was no mention of the skin LD50 for ethanol in the Fischer Scientific MSDS for absolute alcohol.)
Note they are all listed as having the same NFPA Health rating of "2 Moderate". (The NFPA is the organization that came up with the safety diamond that gives a numerical overview of the general safety of a material - you've seen them on chemical bottles, trucks that transport materials, buildings that store hazardous materials - they are everywhere if you look.)
The NFPA defines a Health rating of 2 Moderate as "Moderately toxic material. Will have one or both of the following characteristics: Intense or continued exposure could cause temporary incapacitation or possible residual injury unless prompt medical treatment is given." Note the use of "Intense or Continued Exposure" here. This is different from a Health rating of "3 Severe" where a material is defined as "Toxic" and "May cause serious temporary or residual injury on short term exposure even though prompt medical attention is given. A known or suspected small animal carcinogen, mutagen or teratogen." That's a big jump in the respective definitions of toxicity.
So is ethylene glycol more toxic than propylene glycol? Yes. But keep in mind that they are on the same order of magnitude of toxicity so they are rather similar in their level of toxicity. Keep in mind that sodium chloride has a health rating of "1 Slight" and a LD50 of 3000 mg/kg while potassium chloride has a health rating of "2 Moderate" and a LD50 of 2600 mg/kg. Same order of magnitude, one makes it into moderate with the other is slight. But neither of them is really a very big health hazard in the amounts and exposures we are using when doing photographic emulsions.
I find the differences and risks in using them small. Do I use gloves with one and not the other? No. I don't actually use gloves with either. Should I wear gloves? I've decided that the concentrations and the amount of exposure do not warrant the use of gloves - I find the risk slight when handling these chemicals. And I am constantly washing my hands when handling chemicals, so that helps decrease risk as well here too.
Now I would like to point out that the decision about using gloves is a conclusion that I have made for myself. Every person needs to make an informed descision about when to use protective equipment. As the time and amount of exposure is small, and the working concentrations are small, I find that it's not worth worrying about the difference between ethylene glycol and propylene glycol. I find it slight. From the numbers above, the risk is about the same as when handling ethanol - I don't see anyone being concerned with they spill a mix drink or a beer on themselves. It's not that big a risk.
And neither ethylene glycol or propylene glycol a known carcinogen, teratogen, mutagen, or any of those other especially nasty chemicals. When working with chemicals in those classes, it is certainly a given that you truly need to match the level of personal protective equipment to the chemical in use.
And I would also like to second PE's suggestion that one needs to be responsible for their own actions. And that's why we all need to sit down and educate ourselves on these hazards. And that includes making sure that our families and pets are not exposed as well. Now that I have a little kid running around, I probably need to better secure my chemicals, which are literally all over the basement.
Well, that's the basics of my thoughts on this subject.
PS - I took a swig out of my bottle of Everclear when I bought it. It was awful!
Last edited by Kirk Keyes; 02-08-2010 at 04:35 PM. Click to view previous post history.
For up from the ashes, up from the ashes, grow the roses of success!
I agree with Kirk. I would like to add the following:
"Ethylene glycol (IUPAC name: ethane-1,2-diol) is an organic compound widely used as an automotive antifreeze and a precursor to polymers. In its pure form, it is an odorless, colorless, syrupy, liquid. Ethylene glycol is toxic, and ingestion can result in death."
And to continue:
"Ethylene glycol is moderately toxic with an oral LDLO = 786 mg/kg for humans. The major danger is due to its sweet taste, thus unlike for other poisons, children and animals are more inclined to consume large quantities of it. Upon ingestion, ethylene glycol is oxidized to glycolic acid which is, in turn, oxidized to oxalic acid, which is toxic. It and its toxic byproducts first affect the central nervous system, then the heart, and finally the kidneys. Ingestion of sufficient amounts can be fatal if untreated."
"Propylene glycol is used:
* As a solvent in many pharmaceuticals, including oral, injectable and topical formulations. Notably, diazepam, which is insoluble in water, uses propylene glycol as its solvent in its clinical, injectable form.
* As a humectant food additive, labeled as E number E1520
* As an emulsification agent in Angostura and orange bitters
* As a moisturizer in medicines, cosmetics, food, toothpaste, mouth wash, and tobacco products
* As a carrier in fragrance oils
* As an ingredient in massage oils
* In hand sanitizers, antibacterial lotions, and saline solutions
* In smoke machines to make artificial smoke for use in firefighters' training and theatrical productions
* In electronic cigarettes, it is used to deliver vaporized nicotine
* As a solvent for food colors and flavorings
* As an ingredient, along with wax and gelatin, in the production of paintballs
* As a moisture stabilizer (humectant) for snus (Swedish style snuff).
* As a cooling agent for beer and wine glycol jacketed fermentation tanks
* As a less-toxic antifreeze in solar water heating systems
* As a solvent used in mixing photographic chemicals, such as film developers
* In cryonics
* As a working fluid in hydraulic presses
* As a coolant in liquid cooling systems
* To regulate humidity in a cigar humidor
* As the killing and preserving agent in pitfall traps, usually used to capture ground beetles
* As an additive to pipe tobacco to prevent dehydration.
* To treat livestock ketosis
* As the main ingredient in deodorant sticks.
* To de-ice aircraft.
* As an ingredient in UV or blacklight tattoo "
"Propylene glycol is metabolized in the human body into pyruvic acid, which is a normal part of the glucose metabolism process and is readily converted to energy.
The oral toxicity of propylene glycol is very low, and large quantities are required to cause perceptible health damage in humans. Serious toxicity will occur only at plasma concentrations over 4g/L, which requires extremely high intake over a relatively short period of time. It would be nearly impossible to reach toxic levels by consuming foods or supplements, which contain at most 1g/kg of PG. Cases of propylene glycol poisoning are related to either inappropriate intravenous use or accidental ingestion of large quantities by children.
The potential for long-term toxicity is also low. In one study, rats were provided with feed containing as much as 5% PG over a period of 104 weeks and they showed no apparent ill effects. Because of its low chronic oral toxicity, propylene glycol was classified by the U. S. Food and Drug Administration as "generally recognized as safe" (GRAS) for use as a direct food additive.
Prolonged contact with propylene glycol is essentially non-irritating to the skin. Undiluted propylene glycol is minimally irritating to the eye, and can produce slight transient conjunctivitis (the eye recovers after the exposure is removed). Exposure to mists may cause eye irritation, as well as upper respiratory tract irritation. Inhalation of the propylene glycol vapors appears to present no significant hazard in ordinary applications. However, limited human experience indicates that inhalation of propylene glycol mists could be irritating to some individuals. Therefore inhalation exposure to mists of these materials should be avoided. Some research has suggested that propylene glycol not be used in applications where inhalation exposure or human eye contact with the spray mists of these materials is likely, such as fogs for theatrical productions or antifreeze solutions for emergency eye wash stations."
"Veterinary data indicates that propylene glycol is toxic to 50% of dogs at doses of 9mL/kg, although the figure is higher for most laboratory animals (LD50 at levels of 20mL/kg).
However, propylene glycol may be toxic to cats in ways not seen in other animals. The U.S. Food and Drug Administration has determined that its presence in or on cat food has not been shown by adequate scientific data to be safe for use. Any such use is considered an adulteration of the cat food and a violation of the Federal Food, Drug, and Cosmetic Act."
So, in the final analysis we probably ingest a lot of PG daily but it is harmless at the levels we ingest due to the metabolic path it takes. Pyruvic acid is a lot less toxic than Oxalic acid. Oxalic acid, I have been told, can actually congeal blood by reaction with calcium in the body. It is found in Rhubarb leaf and during WWII, many people died taking the mistaken advice of the government to consume Rhubarb leaf as a green vegetable.
I got these simple facts from Wikipedia. I have known them in that detail since Biochemistry in grad school.
Thanks for talking about health and safety.
As I am sure some have noticed, it is not an exceedingly "fun" topic, nor is it all that clear cut.
We try to make it clear by classification and pictographs etc., but it can quickly become, well, a bitter, dry topic. Nevertheless, an ounce of prevention....