For those who use sodium hydroxide

What About Bob · Mar 1, 2025

I now have some. One pound of it to be exact. I have never used NaOH before, not even any drain cleaners. It will be one of those chemicals that won't be used a great deal, maybe once in a great while. Mostly for an experiment or two.

I have been to many places for gathering information, even through a soap making channel. I have the safety goggles and will be wearing long sleeved shirts and pants that I don't care much about. For gloves I have a case of 1000 black nitrile gloves, though in my research neoprene might be a better choice? One site recommended using a face shield as well as the safety goggles, yet I have watched a few soap making videos and the soap lady only wore simple safety glasses. Is use of a face shield overkill?

My idea is to mix NaOH separately in cold water and add it slowly with stirring, wait for it to cool down then add it to the part that needs it. I get the idea of an exothermic reaction upon NaOH into water. There are so many discussions on what to use and what not to use for mixing and storing the stuff. I am understanding to avoid anything tin and aluminum due to chemical reactions that create toxic fumes. I have a Pyrex graduate that was to be used for mixing but depending on who you go by that glass isn't recommended, yet again I noticed that the soap lady was using glass and in one of her videos she just plopped the NaOH right into the Pyrex with water in kind of a carefree manner while making the statement to "add the NaOH slowly and to stay far away from those fumes!", lol. Her thermometer reading displayed 177F after adding it.

Stainless steel or temperature proofed plastic were recommendations for mixing. Polyproylene, HDPE or even PET were thrown about for storing, yet one other place said no to using PET. I use a Paterson chemical mixer that is plastic. Will NaOH melt it?

For ventilation many recommended a respiratory mask. I have one, that I haven't even used yet, but the cartridges are for vapors from ammonia, formaldehyde, hydrogen sulfide, etc. Yet, again, according to the soap lady you can use either a respiratory mask or something as simple as an N95 mask. For such a small amount of NaOH are the fumes really that noxious during mixing?

A lot of questions, I know. Information varies depending on where you seek the information. I would be interested to hear what others views are on these things. Thanks

bernard_L · Mar 1, 2025

You did not specify what photochemical you intend to prepare. As an example, see the mixing instructions for part B of thiocarbamide toner:

https://www.digitaltruth.com/products/photoformulary_tech/Formulary%20Thiourea%20Toner%20[06-0045].pdf

(except I suspect that "Sodium Hydroxide(52°C/125°F)" is some copy-paste oversight; no need to heat the NaOH prior to mixing!!)
Do not overdo or overthink it. To be on the safe side, wear a paper mask (leftover from covid) and, (IMO, more important) protective goggles. Add the powder progressively, completely dissolving each time, and monitor temperature; as long as it stays below 50°C you should be fine. Glass should not be a problem on the short term (mixing). Long-term effects seem to be limited, see, e.g.:

Leaching of borosilicate glasses. I. Experiments

The corrosion of sodium borosilicate glasses xNa2O–yB2O3–(1−x−y)SiO2 is studied at constant temperature and pH as a function of the glass composition …

www.sciencedirect.com

Finally, store your hydroxide pellets (flakes? powder?) in an air-tight container. Sodium hydroxide will absorb water vapor, and then, also react with carbon dioxide.

What About Bob · Mar 1, 2025

bernard_L said:
You did not specify what photochemical you intend to prepare. As an example, see the mixing instructions for part B of thiocarbamide toner:

https://www.digitaltruth.com/products/photoformulary_tech/Formulary%20Thiourea%20Toner%20[06-0045].pdf
(except I suspect that "Sodium Hydroxide(52°C/125°F)" is some copy-paste oversight; no need to heat the NaOH prior to mixing!!)
Do not overdo or overthink it. To be on the safe side, wear a paper mask (leftover from covid) and, (IMO, more important) protective goggles. Add the powder progressively, completely dissolving each time, and monitor temperature; as long as it stays below 50°C you should be fine. Glass should not be a problem on the short term (mixing). Long-term effects seem to be limited, see, e.g.:

Leaching of borosilicate glasses. I. Experiments

The corrosion of sodium borosilicate glasses xNa2O–yB2O3–(1−x−y)SiO2 is studied at constant temperature and pH as a function of the glass composition …

www.sciencedirect.com

Finally, store your hydroxide pellets (flakes? powder?) in an air-tight container. Sodium hydroxide will absorb water vapor, and then, also react with carbon dioxide.

I will be using it for an experiment with D-23 developer and also for making a small amount of homemade Rodinal solution.

When the NaOH was ordered there was no description on the fineness or type of NaOH. The container hasn't been opened yet but it sounds like the contents are coarse. When I shake the container it sounds about the same as my container of sodium metaborate contents when shaken.

I know that potassium version is recommended more. A few videos I have seen in the past said sodium could also be used.

Thanks for the Digital Truth and Science link.

koraks · Mar 1, 2025

The risks of working with NaOH in pellet form are generally grossly overstated. Don't sweat it.

What About Bob said:
My idea is to mix NaOH separately in cold water and add it slowly with stirring, wait for it to cool down then add it to the part that needs it.

Sounds fine. I generally just add it directly to the solution I'm making, but your approach will work too.
The solution will heat up a little, but unless your dissolving a lot of hydroxide in a small amount of water, it won't get all that hot. Solutions up to 10% w/v made from tap water won't get dangerously hot.

You can use regular glass or pyrex for mixing. You can store hydroxide solutions in glass bottles; the worst that can (and does) happen is that the glass loses a bit of its shine/lustre on the inside. It's not like the glass will dissolve or anything. PET is OK, too. Tinfoil/aluminum will indeed dissolve.

What About Bob said:
Yet, again, according to the soap lady you can use either a respiratory mask or something as simple as an N95 mask.

You don't need a mask if you're just dissolving NaOH in water. No gases evolve when doing this. It's ridiculous that people are suggesting a respirator for this.

The real risks of handling NaOH and NaOH solutions in practice are:
* Splashing, esp. in the eyes. Work carefully and wear safety goggles.
* Softening of the skin and ultimately chemical burns if you allow strong lye solutions to touch the skin for a prolonged amount of time.
* Damage to materials that aren't resistant to lye, such as aluminum.

Just to illustrate, although not to say that this is good practice (it evidently isn't): I never use safety goggles when handling NaOH pellets in my darkroom for various purposes. I handle the solutions with my bare hands; of course I don't put my hands in there, but I don't bother putting on gloves just to pick up a bottle/beaker of lye solution. If I spill one or two solid NaOH pellets, I generally pick them up with my fingers. It takes some time for them to dissolve, so I simply pick them up and put them back where they need to go. Then briefly rinse hands to get rid of any tiny trace of NaOH dust that may have been left. Similar with minor splashes of lye-containing solutions; just rinse them off.

Of course, I do recommend wearing safety gear and don't be as nonchalant as I am (which is entirely a personal choice). Wear goggles, that's the main thing. Optionally wear gloves; doesn't matter for this purpose whether it's latex, nitrile or whatever (if you have to buy new ones, get nitrile). I don't see why you'd want to wear a mask, let alone a respirator.

dokko · Mar 1, 2025

I handled concentrated sulfuric acid and mixed NaOH solutions for reversal processing without any safety protection (other than being really really careful) when I was young.

I would never do this anymore, not because it's terribly dangerous when nothing goes wrong, but it is if something goes wrong (like, something startles me in the wrong moment).

for sulphuric acid, I simply use 10% solution now (still being careful about splashes).

I don't need NaOH solutions anymore (I use carbonate), but if I'd have to mix it in larger quantities again, I'd wear gloves and safety googles and do it in a ventilated area (possibly outside) because I found the air while mixing was unpleasant to breath in.

What About Bob · Mar 1, 2025

Thanks, Koraks.

At the most I might be dissolving around 20 grams of the stuff. What I found interesting was that the Rodinal recipe called for 20 grams of hydroxide, 50 grams of sulfite and about 30 - 500mg acetaminophen tablets mashed up. Certain chemical places sell the acetaminophen base without all of the extra stuff that is in consumer tablets, like the fillers, starch? dyes, etc, but a small amount of plain acetaminophen was around over $400 for less than 500mg of the stuff. I am adventurous but not that much, lol.

I have a second coffee grinder that I can use for mashing the tablets. Doesn't seem possible to separate the junk from acetaminophen but according to other users that I have witnessed the stuff will develop film, after 72 hours.

The D-23 experiment is one that another forum member was working with. There was an example image of logs and a blade of grass that was so crazily sharp. I have been wanting to try the addition of NaOH to D-23 after seeing that.

dokko · Mar 1, 2025

What About Bob said:
At the most I might be dissolving around 20 grams of the stuff. [...] I have been wanting to try the addition of NaOH to D-23 after seeing that.

I assume you wont be adding the full 20g to 1L of D-23, because if you do, you're likely going to have a massive increase in contrast

What About Bob · Mar 1, 2025

dokko said:
I would never do this anymore, not because it's terribly dangerous when nothing goes wrong, but it is if something goes wrong (like, something startles me in the wrong moment).

Yeah all it takes is something slight to make one jumpy. One thing I could think of that would be startling would be the smoke and fire detectors going off when the apartment people do their occasional alarm testing. Sometimes they don't give notice when doing this and the tests can last for a few hours or more.

I live in an apartment complex where people are out and about constantly. I would get a lot of strange looks by people with mixing chemistry outside. Might even get questioned about it, lol.

koraks · Mar 1, 2025

Yes, the parodinal recipe that you mentioned will work, and it does indeed also work with regular paracetamol tables with all the fillers etc. You'll find that this paridonal concoction throws down a thick, heavy layer of what appears to be a kind of mud in the bottle. Ignore it; it doesn't affect the film in any way. It's mostly undissolved sulfite and the fillers used in the paracetamol tablets.

Keep in mind you don't need to mix the full amount listed; the 20g NaOH 50g sulfite etc. you listed is for 250ml+ concentrate. If this is just to test the recipe, you could also start with a smaller amount; divide everything by 5 or so and see how that goes. Then mix up a larger batch if you like it, although rodinal is of course used in a very dilute form, so I usually end up mixing batches of 50-100ml of developers like these.

What About Bob said:
There was an example image of logs and a blade of grass that was so crazily sharp.

Most of this will be down to other factors than the developer used. In the grand scheme of things, the developer really isn't all that significant.

What About Bob · Mar 1, 2025

dokko said:
I assume you wont be adding the full 20g to 1L of D-23, because if you do, you're likely going to have a massive increase in contrast

The 20 grams would be for the homemade Rodinal. The amount for the D-23 is something like 0.5 grams of hydroxide in either 1+7 or 1+9 dilution of D-23.

What About Bob · Mar 1, 2025

koraks said:
Keep in mind you don't need to mix the full amount listed; the 20g NaOH 50g sulfite etc. you listed is for 250ml+ concentrate. If this is just to test the recipe, you could also start with a smaller amount; divide everything by 5 or so and see how that goes. Then mix up a larger batch if you like it, although rodinal is of course used in a very dilute form, so I usually end up mixing batches of 50-100ml of developers like these.

Sounds good. I do have two 100ml amber glass bottles but I think I will get some 50ml bottles for smaller doses. The recipe was from "FrankenFilm", I believe it was.

koraks · Mar 1, 2025

Yes, you'll find the same recipe in various places. I've made it a few times in the past as well. It worked OK, but in the end I don't really see the point of Rodinal since there's not all that much it does better than any of the other available options. In fact, come to think of it, it doesn't have any clear advantage as far as I can tell. If you want something that's highly concentrated, keeps well, can give high acutance with reduced agitation etc, Pyrocat is what I keep coming back to.

pentaxuser · Mar 1, 2025

What About Bob or anyone else knowing the answer to this most important questíon: Who is the soap lady?

Thanks

pentaxuser

What About Bob · Mar 1, 2025

pentaxuser said:
What About Bob or anyone else knowing the answer to this most important questíon: Who is the soap lady?

Thanks

pentaxuser

Why The Queen of Soap, of course:

and

If I ever feel the need to make any soap I know where to go for all of my soaping needs.

Augustus Caesar · Mar 1, 2025

I use SH in making up FX-21, but it's not really that hard to handle. Only a very small amount is needed in most photographic applications. I add it directly into the solution as I mix it. No need to dissolve it first.

chuckroast · Mar 1, 2025

What About Bob said:
The 20 grams would be for the homemade Rodinal. The amount for the D-23 is something like 0.5 grams of hydroxide in either 1+7 or 1+9 dilution of D-23.

I use 0.5 g/l of working strength 1+9 D-23. I mix it in directly, stirring and pouring slowly (with eye, skin, and clothing protection) and the amount of exothermic response has been unremarkable.

mshchem · Mar 2, 2025

Decades ago I handled a lot of sodium hydroxide, pellets for mixing 30% solutions for Kjeldahl nitrogen assays. I mixed 5 gallons at a time using several pounds of sodium hydroxide. Always done in a fume hood, huge stainless steel kettle, a polypropylene paddle to stir. Gets very hot. I had safety gear, heavy duty rubber gloves, rubber apron, face shield and a lab coat underneath. Lye is very nasty stuff. Dissolves glass, slowly, leaks past valves. Just nasty.
How I never was hurt handling acids and caustics, toxic chemicals. No thanks!

tokam · Mar 2, 2025

Do not store sodium hydroxide in PET containers. A number of years back now a friend gave me a small PET jar with maybe 100g of NaOH crystals and I left it on a shelf in my laundry. A few months later I found that the bottom of the jar had disintegrated and the NaOH had spilled and, of course, had eaten the paintwork on the shelf. Annoying cleanup job ensued including repainting the shelf. In smaller quantities I think it is shipped in HDPE plastic containers, may be best to leave in original sontainers.

koraks · Mar 2, 2025

@tokam are you sure you're not confusing PET and HDPE here? That would make more sense.

mshchem said:
30% solutions for Kjeldahl nitrogen assays. I mixed 5 gallons

There's a big difference between mixing big kettles full of 30% lye vs. mixing 250ml of 10% solution.

tokam · Mar 2, 2025

No, it was an old PET jar that contained peanut butter that had been washed / dried before storing NaOH. See vlog on Pictorial Planet - John Finch 'Making You Own Sodium Metaborate' for comments on NaOH storage. My PET jar dissolved when storing dry NaOH. (If you have a PET soda bottle wash and dry and then put a couple of tablespoons of NaOh in it and place it where you can easily wash away any subsequent spilled NaOH.

koraks · Mar 2, 2025

OK, thanks for confirming. It's interesting since I've had HDPE degraded by RA4 developer replenisher (pH=13). I had always assumed this was due to its alkalinity, but it must be more complex than that, since HDPE in principle should be resistant to even concentrated NaOH solutions.

mshchem · Mar 2, 2025

We stored NaOH solutions in Nalgene PP and HDPE containers no trouble. These solutions scavenge CO2, keep your bottles capped

darkroommike · Mar 2, 2025

Nasty stuff, I wear googles and a rubber apron. I'm also careful about temperature as I mix. The other thing to watch out for is that sodium hydroxide absorbs moisture from the air as it sits on the counter so measure out what you need and put the lid back on your stock jar. I also have the water running in the sink or a pan of water for a quick rinse if I splash, I have never splashed but better to be careful. Potassium hydroxide is just as energetic and needs the same care, some Rodinal recipes call for potassium hydroxide rather than sodium hydroxide.

mshchem · Mar 2, 2025

koraks said:
@tokam are you sure you're not confusing PET and HDPE here? That would make more sense.

There's a big difference between mixing big kettles full of 30% lye vs. mixing 250ml of 10% solution.

What's the point? NaOH in solid form can be tricky, you don't necessarily feel it doing anything. Then you slip off your boot to find a hole in your ankle.

mshchem · Mar 2, 2025

darkroommike said:
Nasty stuff, I wear googles and a rubber apron. I'm also careful about temperature as I mix. The other thing to watch out for is that sodium hydroxide absorbs moisture from the air as it sits on the counter so measure out what you need and put the lid back on your stock jar. I also have the water running in the sink or a pan of water for a quick rinse if I splash, I have never splashed but better to be careful. Potassium hydroxide is just as energetic and needs the same care, some Rodinal recipes call for potassium hydroxide rather than sodium hydroxide.

Yep, all good points. Super hygroscopic, if you leave a pellet sit on a counter you'll find a pool of nasty.

For those who use sodium hydroxide

What About Bob

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