Replenisher - X g / Y g 'replen' - explanation please (+thanks)

[nick mulder]

Hi,

I am mixing up some developers, bleaches, clearing baths and wotnot for some B+W reversal developing of 16mm cine film ...

couple of questions - heres some typical info that I need clarified:

Start w/ 750ml water
Sodium Thiocyanate 9mL / 11.4mL replen
Potassium Bromide 8g / 0g replen
etc...

replenish at 222ml/100ft (16mm cine film)​

Ok - start with water... add some Sodium Thiocyanate, which is expressed in mL amounts - thing is I have it in solid form...

What to do ?

Also I would like to understand what is meant exactly by the two measurements ... Is the first one the initial amount and the second one the amount you add to replenish the solution after a certain time ?

If I am correct that means that when replenishing I add more of the sodium thiocyanate than I did in the first instance ? and I dont have to add any potassium bromide ever ?

I am also not sure about the 222ml/100ft comment - I assume I add more water as the film will carry a certain amount away with it ?

So for every 100ft of film I add 222ml water and the replen amounts of the chems ?

100ft is the 'replen' time ?

I'm only doing 33ft lengths for now and am keen to get some developed quickly so am not worried about the replenishing of chems (yet) - if I am correct about the first listed amount being correct then I'm almost there (been collecting chems and gear for a while now) - just need to know about that mL/g problem with the sodium thiocyanate...

thanks for any help in advance

nick

 

[Nick Zentena]

Which formula is this? It might help others if they knew which one.

Looks like processing the film uses up Sodium Thiocyanate but not the bromide. Odds are the film is releasing bromide in the processing or at least not using it up. I'd guess the m/l numbers are for some sort of solution.

Yup for every 100 feet of film you run you remove enough liquid so when you add back 11.4mL you're at the starting amount. I guess this is for 1 litre? You don't normally add water when you replenish. You add the replenisher which of course is made with water.

But like I said tell us which formulas and people might know better.

 

[nick mulder]

Which formula is this? It might help others if they knew which one.

the site http://www.fortunecity.com/lavender/lavender/569/negtoposdeveloper.html is where I am getting the info.

I couldn't source D94 but have some D19 in which I just need to add the Sodium Thiocyanate. My mention of the pot bromide is therefore redundant but serves to help me understand the replenishing question I have re. the rest of the instructions on that page.

So as I understand it, I was correct ? For a working solution add the 'before the slash' amount and replenish with the 'after the slash' amount ? :rolleyes:

As for my question re the thiocynate g vs. ml question I found some info further down that page - I have to:

Add 5 ml of %51 Sodium
Thiocyanate per liter of D-19

Firstly this says 5ml instead of the 9ml listed earlier on the same page, so I'll take it that the measurement isn't set in stone (it helps with highlights apparently), but what exactly is a %51 mixture ?

Is this info lacking in some way and/or is there a photographers convention when it comes to weights, volumes and % mixtures, perhaps I need to go back to first year chemistry and learn molar masses and the rest ?

 

[john_s]

% solutions are usually grams of whatever it is per 100mL solution. So a 51% solution of sodium thiocyanate would be 51gram of sodium thiocyanate in whatever amount of water to make 100mL of solution. Note that there is not 100mL of water: there is less than that, whatever it takes to make 100mL of solution.

Replenishers generally contain the same ingredients as the developer but in different proportions, to take account of the differences in their being used up. As has been mentioned, bromide is often missing in a replenisher because some of it comes out of the film. Usually a fixed amount of replenisher per unit of film is put into the used developer, and some of the used developer might need to be discarded to make room for all the replenisher. As time goes by, the amount of replenisher required might need to be increased or decreased according to how it turns out: heavily exposed film might exhaust the developer more, etc.

The site you mentioned shows that you need 222mL of replenisher for each 100ft of 16mm film. If you are doing 33ft, then 222/3=74mL would be appropriate, I guess.

 

[Nick Zentena]

http://www.kodak.com/US/plugins/acrobat/en/motion/support/processing/h2415/h2415.pdf

That's the Kodak B&W processing document. It doesn't list D-19 but does provide the formulas for D-94 and D-95. Plus the replenishers.

Might be easier to understand then that webpage.

 

[Gerald Koch]

The amounts of chemicals before the slash are for the composition of the original developer. The amounts after the slash are for the composition of the replenisher solution.

Say you started with 1 liter of solution. After processing 100 ft of film in the developer you would pour off AND SAVE 250 ml of the solution. You would now add 222 ml of the replenisher and enough of the reserved developer to bring the volume up to the original 1 liter. Any remaining reserved developer can now be discarded.

If you are processing only 33 ft lengths then you would add only 222/3 ml of replenisher.

The thiocyanates are very deliquescent and will rapidly pickup enough moisture from the air to dissolve. This is why they are often sold and a roughly 50% w/v solution. Take the amound in grams and multiply it by two to get the amount of the 50% solution required.

 

[nick mulder]

http://www.kodak.com/US/plugins/acrobat/en/motion/support/processing/h2415/h2415.pdf

That's the Kodak B&W processing document. It doesn't list D-19 but does provide the formulas for D-94 and D-95. Plus the replenishers.

Might be easier to understand then that webpage.

thanks, for all the info everyone - I didn't think to search at the Kodak website, something about it being constantly bagged for slowly dropping dropping film products made me think it would be a waste of time - they do however keep up with the Cine stocks ...

I could have searched ! - hopefully this info is helpful for others here too...

Turns out I need to add 6g of the sodium thiocyanate / L - about 'one flat dessert spoon' according to my measurements (;

thanks again