Another Caffenol question, also applies for chemistry in general

[Top-Cat]

So I just recently found out about caffenol, which to me seems like one of the best things that happened to analog photography in the past ten years.

I found out there were a whole lot of different recipes out there and seeing as I'm kind of new to the game of DIY chemistry I found this one to seem like the simplest to follow: http://content.photojojo.com/tutorials/coffee-caffenol-film-developing/

I tried it on Agfa APX 100 with slightly positive results - I got an image, but the image was very weak, as I could hardly see the image on the film itself and could only see it clearly enough after I scanned it.

For my second attempt I tried the same mix, but doubled the development time, I agitated as I usually did (ca 1-2 times a minute) for thirty minutes - I did this as I saw another recipe referring to a development time of fourty minutes, all though with slightly less agitation ( using semi-stand development ) - this time I got similar results, a weak picture, only with an almost black base.

So I'm asking, what do you change to get higher contrast - in the sense that I want a more transparent base and to get it darker where the negatives should be?

Caffenol is comprised of three ingredients (instant coffee, ascorbic acid, and sodium carbonate), and as I've read from skimming through "The Darkroom Cookbook" a developer is usually consisted of several agents, each agent doing it's own job. Should I change the amount of one of the agents? Or is getting higher contrast only a question of the process itself, such as more agitation?

 

[SMBooth]

Here is proberly the best site for your coffee trip http://caffenol.blogspot.com/

 

[Top-Cat]

Dug through "The Darkroom Cookbook" again, and found a quick answer - as far as I can see, it seems that the sodium carbonate (washing soda) acts as an accellerator.

Am I right in thinking I should add more of this to get a higher contrast? It also says that increasing the amount of sodium carbonate might cause fogging, and that I should add some sort of restrainer to prevent this.

As it says caffenol.blogspot.com, both citric acid or salt might work as a replacement for KBr (potassium bromide) as a restrainer, salt being the cheapest and easiest available, preferrably iodized, allthough regular can work as well.

Just thinking out loud here to see if someone who might know better has any objections.

 

[removed account4]

i am not very good with the chemistry part of this developer, even thought it is my main developer ...
from what i can remember developers work best when they are a certain ph, and the washing soda
acts as a buffer to adjust the ph ... the vit c on the other hand increases the speed and the contrast of the developer.
what kind of print developer do you normally use ?
if you ever want to smooth out your developer, boost the contrast and reduce the fog, and you have some ansco 130 handy
add about 10cc / L of caffenol and stand develop your film for about 20-25mins, that is what i do and i get great results.
even with 10 year old shelf stored tmz --

good luck !
john

 

[Trask]

John's typo has created a universal truth: "developers work best when they are a certain oh"

Some people think Rodinal has the oh, other prefer XTol's oh -- it's all in the mojo oh.

 

[Top-Cat]

My experience with developers are: Rodinal (haven't used that in years now though), Xtol and T-Max. For my own darkroom, the one I use now, I just recently went out of T-Max and bought myself a batch of Xtol of which I'm using now.

I don't think the fix (Ilford Rapid) can be trusted as I don't like the colour of it (yellowish), but I'm broke, even too broke for Fomafix, so I'm trying to make the best out of leftovers.

I do have some old Ilford Paper developer lying around, might that improve the recipe? (All though I do like to find a solution using household products, as caffenol is very tempting considering the price, and the availability, as well as the unique qualities of grain and tone)

 

[removed account4]

hate to say this but caffenol isn't very inexpensive, much more expensive than the other developers you mentioned ... more fun though
i can't speak for the ilford developer that you have, i guess you can shoot a test roll and see, don't add too much, just a small amount ... or if the developer is like dektol just dilute it 1:7 ( without the coffee bits ) and process it normally for 7 mins
or if you want to get crazy dilute it with your caffenol 1:7 and see what happens, you might get nice contrast
and other good stuff.
i developed all my film in ansco 130 for years before learning about caffenol.

john

ps trask, you're fast !

 

[Gerald C Koch]

The developing agent identified in coffee is caffeic acid. This chemical is a derivative of catechol which is used in hundreds of developer formulas. The site quoted by the OP says not to use decaffinated coffee. But I think that this warning is based on the incorrect assumption that the developing agent is caffeine. This is not true and caffeine has NO developing action. Since coffee is a natural product the amount of caffeic acid will vary. Robusta coffee contains more of this chemmical than arabica coffee. The amount of caffeic acid can also vary between batches of coffee beans. There are something like 600 different chamicals in coffee and there is a good chance that there are other chemicals present that could act as developing agents.

Vitamin C, ascorbic acid, is also a developing agent and is used in developers like Xtol. It can also act as a preservative much like sodium sulfite. The third chemical in this developer is sodium carbonate which is an alkali. It raises the pH of the solution allowing the two developing agents to work.

Salt, sodium chloride, cannot be used as a restrainer to replace potassiun bromide. Sodium chloride only works with very slow chloride emulsions. This excludes modern films. The only chloride emulsion that I am aware of is in Azo paper. Citric acid also cannot be used as a restrainer.

Fortunately, the best coffee for driinking is made from arabica beans. This leaves the poorer variety robusta to be used as developer.

 

[removed account4]

hi jerry

on the blog site ( http://caffenol.blogspot.com/ ) on the july 11 entry reinhold talks about using it salt as a restrainer.
i know you have a chemistry background, do you have any clues as to what the salt is doing, if it isn't "restraining" ?
as i mentioned i have limited knowledge of what is actually going on ...

thanks in advance for your insights !
john

 

[Gerald C Koch]

For sodium chloride, potassium bromide, and potassium iodide the amount that produces a restraining action is very approximately proportional to the ratio of the solubility products of the silver salts.

[Ag+][Cl-] = 1.7 x 10 -10
[Ag+][Br-] = 4.0 x 10 -13
[Ag+][I-] = 0.94 x 10 -16

You will notice that the solubility products form a decreasing series where each SP is roughly 1/1000 of the previous one. Thus in a developer where 2 g of potassium bromide is used the same restrainer activity could be achieved using 1/1000 of that amount of potassium iodide, or 2 mg. The amount of sodium chloride required however would be 2000 grams! So you can see that using 20 g/l of sodium chloride would have only a very, very slight restraining effect.

Now iodized salt is another matter as its restraining effect comes from any sodium iodide present in the salt. Perhaps any apparent restraing action of the non-iodized salt is based on the placebo effect. Another explanation would be that there may be a small amount of bromide and/or iodide contamination in the non-iodized salt.

Jerry

 

[Top-Cat]

Seems like I should try using iodized salt.

I also happened to find some sort of mix for making jam at the grocery store containing water, fructose, citric acid, some sort of ph-regulator and something for conservation, could this be used for citric acid, or does it contain chemicals that might get in the way?

 

[jp498]

I use the recipe here:

http://www.digitaltruth.com/data/caffenol.php

Scaled up to 1L to develop Fomapan 100 sheet film. I use about 15-17 minutes at 72F. I consider it a lower contrast developer, but not as weak as what you experienced. If you want a higher contrast developer, use something else. I haven't tried the other suggestions on here; they might be fun.

 

[removed account4]

Seems like I should try using iodized salt.

I also happened to find some sort of mix for making jam at the grocery store containing water, fructose, citric acid, some sort of ph-regulator and something for conservation, could this be used for citric acid, or does it contain chemicals that might get in the way?

i would stay away from fruit fresh
there is a long long long thread here called " caffenol tragedy " where
the OP used fruit fresh, it just made a big mess ...
i have heard of others having similar results ...

what brand coffee are you using ?

do you have a bulk loader to you can do small tests instead of
shooting a whole roll ?

how are you exposing your film ? sometimes over exposure can be your friend .

you might also try to print the film you said was "weak" sometimes caffenol film
looks like hazy fog with very little image, but prints ( or numericalizes ) better
than you thought ..

i tend to over process and over expose my film a little bit and my film is usually
pretty dense but it is tuned to the way i print .. my earlier film was thin like
yours was ..

 

[Gerald C Koch]

Seems like I should try using iodized salt.

I also happened to find some sort of mix for making jam at the grocery store containing water, fructose, citric acid, some sort of ph-regulator and something for conservation, could this be used for citric acid, or does it contain chemicals that might get in the way?

No, you cannot use this mix. Citric acid cannot be used as a restrianer. Sodium bromide can sometimes be bought from a pool supply store. It is used to brominate rather than chlorinate pools.

 

[Athiril]

For sodium chloride, potassium bromide, and potassium iodide the amount that produces a restraining action is very approximately proportional to the ratio of the solubility products of the silver salts.

[Ag+][Cl-] = 1.7 x 10 -10
[Ag+][Br-] = 4.0 x 10 -13
[Ag+][I-] = 0.94 x 10 -16

You will notice that the solubility products form a decreasing series where each SP is roughly 1/1000 of the previous one. Thus in a developer where 2 g of potassium bromide is used the same restrainer activity could be achieved using 1/1000 of that amount of potassium iodide, or 2 mg. The amount of sodium chloride required however would be 2000 grams! So you can see that using 20 g/l of sodium chloride would have only a very, very slight restraining effect.

Now iodized salt is another matter as its restraining effect comes from any sodium iodide present in the salt. Perhaps any apparent restraing action of the non-iodized salt is based on the placebo effect. Another explanation would be that there may be a small amount of bromide and/or iodide contamination in the non-iodized salt.

Jerry

I believe iodised salt is an iodate however.

Seems like I should try using iodized salt.

I also happened to find some sort of mix for making jam at the grocery store containing water, fructose, citric acid, some sort of ph-regulator and something for conservation, could this be used for citric acid, or does it contain chemicals that might get in the way?

You can just buy citric acid in the supermarket in the baking section, should be near tartaric acid as well.


OP needs; more developer action, more restrainer, so more developing agent and/or higher pH and some bromide. Asocrbic acid would go a long way to increase activity.. it will drop pH too unless you add more base, or react the ascorbic acid with a base before adding it.


Chris, what country are you from? edit: Oslo in Norway nevermind.

 

[Gerald C Koch]

Concerning my previous post on the use or non-use of decaffinated coffee. It is possible that some of the decaffinating processes could decrease the amount of caffeic acid. Although it is claimed that the carbon dioxide - water method used most commonly specifically removes only the caffeine. Since decaf brands are usually more expensive this would not seem to be a real problem.

 

[Gerald C Koch]

I believe iodised salt is an iodate however.

Yes, but there may be some iodide also present. Iodate ion is an oxidizing agent and will be reduced by contact with organic material such as coffee.

 

[Athiril]

Yes, but there may be some iodide also present. Iodate ion is an oxidizing agent and will be reduced by contact with organic material such as coffee.

So that would waste caffeic acid?

I've read somewhere from some caffenol enthusiasts decaf contains less caffeic acid for some reason. Can't remember though.

To confirm about the caffeine thing, I've also tried pure caffeine extract powder as a developer just to be sure, there was no activity.

edit: Found this on the wiki page;
"Potassium iodate is sometimes used for iodination of table salt. Because iodide can be oxidized by molecular oxygen to iodine under wet conditions, US companies add thiosulfates or other antioxidants to the potassium iodide. In other countries, potassium iodate is used as source for iodine."

 

[Gerald C Koch]

So that would waste caffeic acid?

I doubt it, there are probably many compounds in coffee that would be easier to oxidixe.

Checked the salt in my cupboard. It contains potassium iodide and 1.5 g (1/4 tsp) supplies 45% of the Minimum Daily Requirement. The MDR is 150 ug. Doing the math 1.5 g contains 67.5 ug of potassium iodide or 0.0675 mg.

 

[Murray Kelly]

Just for the record Google Cinnamic acid and compare with the caffeic acid, hydroquinone and catechol structures. The hydroxyl radicals are just in the right place.

I was sceptical myself but am becoming convinced it is a perfectly reasonable replacement for 'regular' developers albeit somewhat slow. It needs carbonate to work at all well but the grain is very fine. I am getting 50 ISO with PolyPan F no worries. I like the tonality - I am no fan of contrast.

 

[Monito]

You may be able to get Potassium Iodide (KI) from your pharmacist as SSKI: Saturated Solution Potassium Iodide.

 

[Athiril]

Wouldn't that be 88.3µg of KI?

You may be able to get Potassium Iodide (KI) from your pharmacist as SSKI: Saturated Solution Potassium Iodide.

You can get the dry salt off ebay for about ~$20 for 100g.

 

[Gerald C Koch]

Wouldn't that be 88.3µg of KI?

0.45 x 150 ug = 67.5 ug

 

[Gerald C Koch]

If you are going to be buying a restrainer other than iodized salt then potassium or sodium bromide is a better choice. Since so little iodide is required it would be hard to measure for most people. The only time I have seen a requirement for potassium iodide is for the Beutler formula where 25 ml of a 0.001% solution is added to 1 liter of the concentrate.

 

[removed account4]

Concerning my previous post on the use or non-use of decaffinated coffee. It is possible that some of the decaffinating processes could decrease the amount of caffeic acid. Although it is claimed that the carbon dioxide - water method used most commonly specifically removes only the caffeine. Since decaf brands are usually more expensive this would not seem to be a real problem.

i think many of the coffee companies use dichloromethane as their preferred decaf method, the swiss water process, while it doesn't leave chemical residue that burns off
during the roast, it is more expensive, and the coffee "flavor" is reduced.
i don't know for sure, but maybe the coffee companies use arabica coffees
for their decaf-instant so it is more flavorful, seeing the decaf-process
robs coffee of taste. ( and cheap robusta beans are usually used as a filler )...
and more arabica beans = more cost/more expensive coffee.

while i am probably wrong, and it is only a guess, it seems that might be a reason
why decaf instant isn't recommended ... ( the wrong kind of beans )