Equivalent Sodium Hydroxide to Sodium Carbonate

I use 80 grams of Sodium Carbonate and fill to 500ml of water, what is the equivalent amount of Sodium Hydroxide in 500ml of water? The sodium carbonate forms a very flaky and thick solution that ends up producing "snow" on my images, wheras from my use of black and white Sodium Hydroxide developers, it leaves no marks. Both accomplish the same thing: making the solution very alkaline. I want to switch over to using Sodium Hydroxide to make things easier, but I dont want to poach it with too much, as around 100+ grams of Sodium Carbonate to 500ml, it starts to bleach some fuji films.

Sodium carbonate has a PH of 11, Sodium Hydroxide a PH of 14. I understand that the concentration is what matters here, and I think the 80 grams of sodium hydroxide put it in league with about 5 grams of Sodium Hydroxide? (educated guess from what I know about its use in high contrast developers)

warrebphoto said:

Sodium carbonate has a PH of 11, Sodium Hydroxide a PH of 14.

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No.
That's not a meaningful statement. You can compare the 'strength' if you will of both by comparing their pKa, or by comparing the pH of a solution of either chemical with the same molarity.

warrebphoto said:

I understand that the concentration is what matters here

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Yes, but also buffering behavior. Sodium carbonate is itself a buffer, whereas hydroxide needs additional ions present in order to form a buffer. This is relevant if there's not just hydroxide or carbonate in your solution and this is indeed the case when developing film. Even ions leaching from the gelatin emulsion itself will start to form a buffer with the present hydroxide, and then there's the matter of other chemistry in the developer. All this means that there's no easy substitute of x grams sodium hydroxide for y grams of carbonate. It's far more complex than that. The pH of a hydroxide solution will shift as you add stuff to it, while a carbonate solution will be more stable. In addition there are likely distinct differences in how carbonate and hydroxide interact with other chemistry.
You probably can get plenty close enough for your purposes by entering the target pH in one of the calculators online and then use that as a starting point: e.g. https://sensorex.com/ph-calculator/
You can get the target pH by calculating or better yet measure the pH of your known carbonate solution.

warrebphoto said:

as around 100+ grams of Sodium Carbonate to 500ml, it starts to bleach some fuji films.

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I suspect you'll run into problems with the emulsion lifting off from the film if you're going to use any significant amounts of hydroxide. YMMV.

Out of curiosity, what are you trying to accomplish? Boosting contrast? If so, I expect you'll run into a limit anyway that makes it not sensible to work in the rather absurd pH range you're targeting.

I didn't know the answer to this, so I was curious to look it up. In their book 'Developing' (Focal Press, 1970, updated 1978) Jacobson & Jacobson say the following:

<<
Caustic Alkalies
These are much more energetic in their action than the
alkali carbonates, and are only used in those cases where
a powerful and quick-acting developer is required. As might
be expected, developers compounded with caustic alkali
have poor keeping properties and are soon exhausted. The
reason for this difference in properties between developers
compounded with carbonates and those made with caustic
alkalies is of sufficient interest to call for a little special
explanation.
When sodium carbonate is dissolved in water, part of it
is split up, or as the chemist calls it, hydrolysed. As a result,
caustic soda and bicarbonate of soda are formed although
only in small quantities at any one moment. When develop-
ment is taking place the caustic soda or sodium hydroxide is
used up and as that happens more carbonate hydrolyses.
Hence the carbonate acts as a sort of reservoir of caustic
alkali. If we had caustic soda in place of the carbonate to give
the same alkalinity, it would soon be used up and the activity
of the developer would cease. Obviously the use of sodium
carbonate allows us to use a small concentration of alkali
and get the utmost work out of it. The above explanation
also shows why it is rarely possible to substitute caustic
alkalies for carbonates in normal developers.
>>

They go on to say that it is better (in terms of consistent results and keeping properties) to use a relatively strong solution of a mild alkali, rather than a weak solution of a strong alkali. Bearing this in mind, you might want to consider sodium metaborate, which you can make in solution using sodium hydroxide and borax (see this other thread) so it would avoid the use of carbonate as you require. I made a note from somewhere that 1g of metaborate is roughly equivalent to 2g of carbonate.

I hope this helps. Let us know the outcome!

It's just as koraks said. To reinforce one point: yes, you can adjust the pH of a NaOH solution by dilution. But it is a strong base and will hold pH to a high dilution. Once you come down to pH11 it will be so dilute that relatively small changes will change the pH a lot. Or properly stated, as Koraks did, it will be insufficiently buffered.

The answer is that NaOH is not useable on its own for pH11. You need to look up a suitable buffer.

warrebphoto said:

I use 80 grams of Sodium Carbonate and fill to 500ml of water, what is the equivalent amount of Sodium Hydroxide in 500ml of water? The sodium carbonate forms a very flaky and thick solution that ends up producing "snow" on my images, wheras from my use of black and white Sodium Hydroxide developers, it leaves no marks. Both accomplish the same thing: making the solution very alkaline. I want to switch over to using Sodium Hydroxide to make things easier, but I dont want to poach it with too much, as around 100+ grams of Sodium Carbonate to 500ml, it starts to bleach some fuji films.

Sodium carbonate has a PH of 11, Sodium Hydroxide a PH of 14. I understand that the concentration is what matters here, and I think the 80 grams of sodium hydroxide put it in league with about 5 grams of Sodium Hydroxide? (educated guess from what I know about its use in high contrast developers)

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What do you mean by "flaky" solution - are you getting precipitations?

I'm curious to know which developer requires 160g/l of Sodium carbonate. That seems to be a rather excessively high amount of Sodium carbonate for a film developer. Do you mind sharing the developer formula?

nmp said:

What do you mean by "flaky" solution - are you getting precipitations?

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Since I am using so much carbonate in such a small amount of water, it ends up becoming extremely cloudy and does not fully dissolve in the water somehow. This ends up creating a visual snow on my negatives. Since I have used sodium hydroxide in high contrast B&W developers I thought it would be better to use a few grams of hydroxide instead of 80 grams of carbonate

Raghu Kuvempunagar said:

I'm curious to know which developer requires 160g/l of Sodium carbonate. That seems to be a rather excessively high amount of Sodium carbonate for a film developer. Do you mind sharing the developer formula?

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very high saturation color developer
Sodium Sulfite - .5g
Potassium Bromide - .7g
Sodium Carbonate - 80g (standard 12.8g)
Sodium Bicarbonate - 8g (standard 1.4g)
CD3 Color Developer - 2g

I have been using this formula for many years now. It has really nice color, but I do not like the snow dot effect it gives. It isn't dust, as they are visible in the negatives. It works best for slide film that is processed as a negative.

warrebphoto said:

Since I am using so much carbonate in such a small amount of water, it ends up becoming extremely cloudy and does not fully dissolve in the water somehow. This ends up creating a visual snow on my negatives. Since I have used sodium hydroxide in high contrast B&W developers I thought it would be better to use a few grams of hydroxide instead of 80 grams of carbonate
View attachment 306347

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One more question - are you using plain tap water or distilled water. If former, and if it is hard - there might be calcium carbonate formation which is insoluble and precipitates out.

Ok, but it appears to be a little weird modification of the color developer - so much carbonate and some bicarbonate too! Is that strictly needed to get high saturation results? Wouldn't increasing pH of your 'standard' developer by just adding some Sodium hydroxide (say 1g) to it work?

lantau said:

It's just as koraks said. To reinforce one point: yes, you can adjust the pH of a NaOH solution by dilution. But it is a strong base and will hold pH to a high dilution. Once you come down to pH11 it will be so dilute that relatively small changes will change the pH a lot. Or properly stated, as Koraks did, it will be insufficiently buffered.

The answer is that NaOH is not useable on its own for pH11. You need to look up a suitable buffer.

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Should I try to just add bicarbonate to the solution? or well that would make metaborate though hmm.

Below is the highest B&W contrast developer I have used. I think the high sulphite content would counteract the high PH? as I know increasing the sulphite decreases the saturation. But then again it does produce high contrast, which means it must still be acting strongly.

Very High Contrast D178 (Jacbonson's developing)

Hydroquinone 23g
Sodium Sulphite 45g
KBr 15g
Sodium Hydroxide 9g

(This stuff is extremely fast acting, dev times 1-2min)


I wonder if a color developer like this would work, sulphite acting as the buffer? Im not too knowledgeable.

Sodium Sulfite - 10g
Potassium Bromide - 3g
Sodium Hydroxide 3g
CD3 Color Developer - 2g

nmp said:

One more question - are you using plain tap water or distilled water. If former, and if it is hard - there might be calcium carbonate formation which is insoluble and precipitates out.

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I have always used tap water. I could try to use distilled water next time too

Raghu Kuvempunagar said:

Ok, but it appears to be a little weird modification of the color developer - so much carbonate and some bicarbonate too! Is that strictly needed to get high saturation results? Wouldn't increasing pH of your 'standard' developer by just adding some Sodium hydroxide (say 1g) to it work?

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That is a smart idea actually. Would the sodium hydroxide have a reaction with the bicarbonate though? The only official use of sodium hydroxide in color developers is in E2/3 reversal color developer, which I have tried to make myself, recipe below. (I never did a good test to see if it actually worked, but it did not work on the crappy 126 film I tested.)

Trisodium Phosphate 20g
Sodium Hydroxide 2.8g
Sodium Sulfate 25g
Potassium bromide 5g
CD3 5g

This reference gives the solubility of sodium carbonate anh as 170g/L at 20C:
Since your solution contains 160g/L the flakes may result when it cools down.
I would suggest just try 100g/L, the pH is not much affected by concentration at these levels:
Such flakes can usually be filtered out with cotton wool in a funnel.

warrebphoto said:

That is a smart idea actually. Would the sodium hydroxide have a reaction with the bicarbonate though?

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The original purpose of bicarbonate in your 'standard' formula, I guess, is to get a pH slightly lower than what 12.8g of carbonate would give you. If you will be increasing pH of your developer by adding Sodium hydroxide, you might as well remove bicarbonate from the formula.

Your formula looks like it is derived from ECN2 developer. It has more of everything than what you stated as the standard concentrations. But a lot less than what you are using.

I assume you are using normal C41 film? I guess it is a clever trick. CD3 is the wrong colour developer, but keeps the contrast down. Raising the pH increases activity and will develop more colour dye. I doubt the colour curves will match. But this is an effect developer. So who cares, as long as you like the results.

My guess, too, would be tap water causing Calcium carbonate precipitation. Especially at those massive concentrations of carbonate. From a chemists view, the recipe calls for a simple solvent called water. The stuff that comes out of the tap isn't that solvent. It is an aqueous solution of various salts. Best to use demineralised water. I prefer that over using a sequestrant.

Further it may depend on your way of mixing. If you add the Sodium Carbonate too fast it may clump a litte. Bits of material encased in solidified Sodium Carbonate Hydrate. I learned that it is difficult to do lab work without a decent lab. But I have a magnetic stirrer, now. That makes it easier. So add slowly and stir really well. If necessary filter before adding the CD3.

It's also best to keep the carbonate/bicarbonate ratio. It is a buffer. I'm not sure if it is that great and idea to scale up a buffer to such concentrations because activies are not proportional to concentrations anymore, when the latter goes up.

But better to just keep doing what worked and not think too much about it. Unless the other remedies don't work and this turns out to be the actual cause. We can still work on it then.

You all make very good points, I have bulk loaded a lot of very slow color film that I will use for testing purposes. I am going to mix both of these with hot bottled water, slowly. I might do it later today or tomorrow.


Color Dev Trial 1 (based off of the strong B&W developer)
Sodium Sulfite - 10g
Potassium Bromide - 3g
Sodium Hydroxide 4g
CD3 Color Developer - 2g

Color Dev Trial 2 (Normal recipe with added hydroxide)
Sodium Sulfite - .5g
Potassium Bromide - .7g
Sodium Carbonate - 12g
Sodium Hydroxide 2.5g
CD3 Color Developer - 2g

Have you tried leaving out the sulfite altogether? This should boost dye formation.

koraks said:

Have you tried leaving out the sulfite altogether? This should boost dye formation.

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Yes I usually use .7g, which is such a pitiful amount it doesnt do much. I think the sulfite is there to keep it from expiring after one use, but it also limits the saturation. Usually I get about 8 rolls from my normal recipe but I only recommend 4-5 36 exp rolls. I mix to 500ml though, not to 1000ml.

AFAIK sulfite is a quite powerful dye formation inhibitor, so the .7g might just be rather significant. It's part of the reason why sulfite isn't usable as a preservative in C41 formulae. The small quantity of sulfite present is there to achieve the correct color balance which doesn't sound very necessary in your case.

warrebphoto said:

it also limits the saturation.

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Hence my suggestion. I'd give it a try.

Sorry for taking so long to get back, but the results were not really anything special. Trial 1 was a complete failure and WAY too much, it bleached the neg. Trial 2 was able to develop fine, and is probably good for normal use with perhaps a bit less hydroxide? The only issue (which many have stated above) is that it will go bad after a few rolls because hydroxide expires quickly. I got a very blueish final image, but I assume thats because these were taken indoor with a disposable camera on its flash (first image) (found exposed).

Overall, results inconclusive. I will probably just stick to the old recipe, but mix with only about 50g carbonate because any more is just not doing much. Last time I mixed it with 30g carbonate plus 30g bicarbonate and it seemed to produce no spotting. (second image) (recipe scaled to 500ml, double values for 1L)