View Full Version : safety issues when working with chemicals

04-11-2007, 10:21 PM
Hello PE (and anyone else who has this information),

With all the posts regarding (and enthusiasm for) making our own film, I do not recall seeing any posts detailing safety measures one must take when working with the various chemicals used in emulsion making.

Can you please spend some time describing safety precautions that we should be aware of when dealing with the various components of emulsions, and during their handling?

Also, if you have details on any protective safety equipment that is needed when mixing these chemicals, can you please pass them along?


Bob Mazzullo

04-12-2007, 07:32 AM
The first things that come to mind are just basic lab safety.
Read the MSDS, wear appropriate PPE, don't eat or drink while handling chemicals, wipe up spills - generally keep the lab clean and tidy, store things safely, ensure proper ventilation, have a first aid kit handy etc.

Most of which we should all be doing in our respective darkrooms anyway :)

PE or others can probably fill you in on specific hazards of the chemistry used, but a good read of the MSDS would help too.

Photo Engineer
04-12-2007, 10:26 AM
The most immediate hazards are the silver nitrate which can burn you or leave dark stains on your skin, and the hardners which are not very good on contact with skin. Both silver nitrate and hardeners are poisons.

After the emulsion is precipitated, and before the hardener is added, it is pretty benign and not very harmful unless you accidentally drink it.

The metal salts and organic restrainers are also somewhat toxic.

All of these ingredients are used at such low concentrations they are harmless in the final coating, or they react fully while drying and are rendered harmless for the most part.


06-07-2007, 10:25 AM
Here is a descriptive USDA web site with some chemical handling safety information. Some of the entries pertain to some of the chemicals used in emulsion making:



Bob M.

Mike Wilde
06-07-2007, 10:41 AM
http://www.physchem.ox.ac.uk/MSDS/ - heaps of good information there.

I have a binder labelled MSDS in large letters on the spine in the darkrrom, and my wife knows that it is there too. Every bit of raw chemistry I buy, I look to the oxford site for the MSDS for it, and print it out. If the common name is not on the msds, I write it at the top of the page. The name of the chemical is high lited, and filed in the binder in alphabetical order of the highlighted chemical name. That same name is placed on the bottle/ bag/pail of chemistry.

Mixed chemistry if it is a recurring thing will have the chemical formula written with a sharpie pen onto masking tape and stick to the bottle.This speeds up things when mixing more fixer. stop bath, blix, etc.

With developers I just write on the masking tape label the date mixed, the formula name and a reference to the page in the darkroom cookbook, my film processing ringbound notebook, etc, to let me know where the formula is recorded.

The other safety issue is good ventialtion. Lots of other threads have discussed this issue.

06-07-2007, 11:40 AM
Thanks Mike...

Besides the web site, having a binder with all the relevant MSDS information inside and having someone else in the house know what it is and where it's kept could make all the difference in a tight situation.

If you have any other safety information, or precautions we should know about, please pass them along.

Bob M.

Mike Wilde
06-08-2007, 10:03 AM
I use a lab coat over street clothes when mixing concentrated developers, etc. After the session I drop it sraight into the washing machine in the adjacent laundry room. That way anything that got on me doesnt travel too far.

I wear closed toed shoes - no flip flops or sandals. This habbit comes from an splash oops when making soap (done in the darkroom, as another hobby) a few years ago.

I wear glasses, and have goggle that fit over them that I wear when mixing concentrates. If I am working with glacial acetic acid, sulfuric acid, 40% soduim hydroxide etc. I put on a full face shield.

I have yellow 'dishwashing' gloves that I wear when goggles whenever I mix the full stringth acid, & hydroxides.

When working with hydroxides I prefer to make stock solutions up front because the stuff otherwise will rip water vapour straight out of the air, and turn itself into a sticky mass that is then impossible to handle, and also will not weigh properly. When mixing hydroxide stock solutions (if you ever do - there are ways to never have to deal with strong acids and alkalis in this hobby too) start with half the weighed water as ice. It will melt soon enough. It prevents the solution from boiling from the hydroxides liberated heat of hydration.

If I didn't mix my own chems, the darkroom would be at positive pressure to keep household dust from entering. I make soap, make wine and vodka, and mix chems in my darkroom, so I run it at negative pressure, to get the smells that happen in there out side of the house.

I have the HRV for the house routed to suck its exhausing air out at the end of my sink, next to where the fixer or toner tray usually sits. I turn the HRV on high speed and pu the scale right next to the inlet on a board of melamime that bridges the sink when scratch mixing. That way any sulfite dusk, hydroquinone needles, etc go outside before they can settle on any other surface and otherwise dust and chemcally contaminate the darkroom.

I alos have a full mouth and nose washable filter felt type mask that I occasionally use, like if I mix a sulfide toner. In summer this happens at the picnic table which is hosed down immediately therafter, but here in Canada in February that is not an option.

The floor gets wiped with damp cloth ocassionally and the mop cloth while still wet gets bagged and tossed. The rest of the place gets vaccuumed when I get too annoyed at the amount that I must spot on prints. the vaccuum is a central type, so the smallest dusk is not recirculated in the house like conventional vaccuums can do.

06-08-2007, 10:58 AM
Thanks again, Mike....

The trick about using ice has probably saved my bacon from a potential accident, because I never would have thought of it. If I ever make it up to Ontario again, lunch is on me.

When you do have time, can you please detail some of the procedures for dealing with strong acids or bases you mentioned, or perhaps point me in the right direction?

Bob M.

Mike Wilde
06-11-2007, 10:20 AM
The liquid concentrated acids I keep in my stocks are all stored in plastic nalgene type jugs with good fitting lids that my supplier - Claire at JD Photochem - ships to me.

I have a bit of sulfuric (pH lowering of developers, fixers), 31% hydrochloric (aka muratic) (some intensifiers, also good for concrete patches, and a safe place to store it is here) , and acetic (makes RA-4/C41 one shot stop bath) on hand. They live on a high shelf one their own; less likey to get disturbed there, and out of the reach of my kids (now 4 and 7). They are purposefully not stored near basic chemicals.

The kids know that they are not allowed in the darkroom unless dad is with them, and they are invited in.

The powerful acids get measured off sitting in the darkroom sink, where lots of water is easily at hand to rinse off any spills, and quickly rinse out any measuring equipment. Usually a little of a concentrated acid is all that is needed, so I save the little graduated cups that are found over the lids of cough syrup. I pour the required acid into one of these, then it is easier to add it bit by bit to adjust pH, or add the measured amount to the liquid solution. You all know the value of gloves, goggles, and a paddle to disperse the acid I hope. I find that stirring just before the acid goes in prevents micro boiling as it reacts with any base present to form the required buffer. Remember, always acid to water, and if not, as in a spill, always lots of water to rinse.

The other more minor special use acids - boric, citric, edta, oxalic, etc are dry powders and I store them in thier own labelled tightly capped plastic jars on a shelf mixed in with other dry chems. I for a long time salvaged washed vitamin pill bottles (and cough syrup bottles for liquid stock solution storage), to deal with chems that arrive in other than a good storage container. These small bottles and jars also allow me to keep a 'working stock' in the handy sink side cabinet, while the larger overstocks of the chemical live in old cheeze whiz etc jars in the bottom drawer of my enlarger desk (it is a big drawer). There is nothing magic about the sink side dry chemistry cabinet - just there is no need to vaccuum a ton of litte bottlles and jars when I am on a dust hunt.

The most powerful base is soduim hydroxide. Most darkroom rats can get by without it, unless you are into lith developers, etc. Because another mad habit of mine is home made soap ( domestic and craft sale scale productiuon) I buy it in a large (25kg) bag, and store it in two 5 gallon pails with well gasketted lids. It is vastly less expensive per kg than buying the little bottle of Red Devil drain cleaner lye, but that is the same stuff.

The transfer of the sodium hydroxide micropellets from the well sealed multilayer bag to the two pails is tricky. I cut a sheet of plastic to cover the laundry room floor (left over from a home reno), and have the laundry room sink full of water before beginning. If the pellets get away from me ( some do) they land on the plastic. After the transfer, I get a wet rag, and wipe down my shoes. I then fold up the plastic from the outside towards the middle and toss it.

I store my hydroxide as a 40% stock solution. It can be bought this way also. I have tried 50%, which is also sold commercailly, and large crystals formed after the solution had cooled- it was a PITA to re-dissolve them.

I have a 1 gallon stainless vat that sits on a magnetic stirrer (retro fitted with a coffee perk heating element clamped under the stir table to heat a beaker when heat is needed). I get the pre-weighed ice (about 50% of the totoal mass of H2O that will be needed and some measured amouint of liquid water spinning to prevent the ice from all clumping up. I then use an empty margarine tub to scoop and weigh the approx NaOH weight needed. I weigh it, subtract the weight of the margarine tub, then add the contents gradually to the swirling mix of ice and water. With gloved hand, rinse the tub in th solution, as some pellets will still be adhering to it. I then add any needed water (1mL equals 1gram when it is just water) to bring the solution to 40% NaOH by weight.

Do use anything that cannot take heat. Pyrex measuring cups are fine. Stainess steel is fine. Aluminum is not; it is consumed and the pot and aqueous solution are both ruined. Plastic may melt. The reaction generates lots of heat. If it boils, leave the room; do not breath the vapours.

You need to calculate the molecular weight of NaOH and H2O to make this 40% by weight solution work (think CRC handbook or periodic table of the elements- rememeber high school chemistry?). I pre work an ideal example, then work out the amount I am actually dealing with as I go. I tape saran wrap over a calculator, to keep the rinsed gloves from dripping water into the calculator keys. Dont take your gloves off until everything is washed up.

Once the hydroxide solution has somewhat cooled, pour it off into a glass storage bottle dedicated to the purpose, and put on a snug fitting lid. Tighen the lid once the solution is at room temperature. The solution will slightly etch the bottle, and also soduim carbonate will form around the inside at the top (as the hydroxide rips the O from CO2 in the air each time the bottle is openned to make OH and O into H2O).

After the hydroxide to stock solution is in the bottle, still with all lab coats, rubber gloves, and goggles on, take dying j-clothes from the kitchen and use them to wash everything and adjacent surfaces with lots of water. The pellets once they abosrb water feel kind of slippery like they are soap. If you feel anyting tingly and soapy on your skin, load on heaps of water, and you will already have a minor burn. Leave it there, and the hydroxide rips the fats from your skin to make soap, and leave a hole hwere the fats in your skin used to be. After wash up, put the lab coat or what ever was your top layer of clothing into the washing machine.

The less powerful bases are much more commonly used. Most of my B&W print developers are made alkaline with good old fashioned Arm and Hammer washing soda - sodium carbonate. 20 Mule Team borax also is used, as well as paint prep targetted Tri Soduim Phosphate as well as more strictly photo purposed soduim metaborate (aka Kodalk) potassium carbonate, and TEA. These are generally stored on their own shelf in the dry chemistry cabinet.
(except in winter, when the TEA (RA-4 developer) sits on top of a heating duct - it freezes at 20C).

Just because an acid or base is less powerful than sulfuric or hydroxide they may still be an irritant. Wear gloves, if only surgical types. if you are going to handle them. I use stainless steel measuring spoons for most of my work with them to keep my hands from touching the chemicals. I weight them in throw away dixie cups that I place on the pan of an old triple beam banace that is tared to cancel out the cups weight.

06-11-2007, 10:41 AM
Good Grief!

I remember the saying about an "ounce of prevention is worth a pound of cure"....I think you just gave us a pound of prevention.

Many thanks for your time and very valuable information. You can bet I will be using a lot of these procedures personally.

Bob M.