Hi All,

What is your favourite collodion formula? What salted collodion you use from day to day? And do you adjast your formula for hot or cold weather?

---------

I use formula from Quinn forum (http://www.collodion.com/forum).

PART A
250ml Plain U.S.P. Collodion
160ml Ether

PART B (this needs to be mixed over an alcohol lamp)
3g Cadmium Bromide (will cake up in water - break apart and dissolve over the alcohol lamp.
5ml Distilled Water

PART C
This is PART A and PART B Mixed together

PART D
4g Potassium Iodide
5ml Distilled Water
160ml Grain Alcohol

Slowly mix PART D into PART C and shake after every addition.

---------

But after I've made some research and found that KI and CdBr2 may be dissolved in alcohol I want to change this formula and will try new one:

PART A
250ml Plain U.S.P. Collodion
160ml Ether

PART B
3g Cadmium Bromide
4g Potassium Iodide
160ml Grain Alcohol

Slowly mix PART B into PART A and shake after every addition.



Edited 2 time(s). Last edit at 04/12/2007 03:34AM by unrealalex.

unrealalex Wrote:
-------------------------------------------------------
> Hi All,
>
> What is your favourite collodion formula? What
> salted collodion you use from day to day? And do
> you adjast your formula for hot or cold weather?
>
> ---------
>
> I use formula from Quinn forum
> (http://www.collodion.com/forum).
>
> PART A
> 250ml Plain U.S.P. Collodion
> 160ml Ether
>
> PART B (this needs to be mixed over an alcohol
> lamp)
> 3g Cadmium Bromide (will cake up in water - break
> apart and dissolve over the alcohol lamp.
> 5ml Distilled Water
>
> PART C
> This is PART A and PART B Mixed together
>
> PART D
> 4g Potassium Iodide
> 5ml Distilled Water
> 160ml Grain Alcohol
>
> Slowly mix PART D into PART C and shake after
> every addition.
>
> ---------
>
> But after I've made some research and found that
> KI and CdBr2 may be dissolved in alcohol I want to
> change this formula and will try new one:
>
> PART A
> 250ml Plain U.S.P. Collodion
> 160ml Ether
>
> PART B
> 3g Cadmium Bromide
> 4g Potassium Iodide
> 160ml Grain Alcohol
>
> Slowly mix PART B into PART A and shake after
> every addition.

Do more "research" and you will "discover" that when you put Cadmium Bromide and Potassium Iodide together in solution they make some Potassium Bromide which is not soluble in alcohol. This Potassium Bromide comes out of solution, making room for the fomation of more Potassium Bromide until all the Bromide in the alcohol has been converted to Potassium Bromide.
In any reversable chemical reaction, removing one of the products of the reaction from the mixture by whatever means (like precipitation) will cause the reaction to shift in the direction of the removed product, in this case KBr, trying to restore the equilibrium. This continues to occur until one or both of the components (K or Br) of the precipitated product are used up.
Putting more water in the alcohol or collodion will cause some of the Potassium Bromide to remain in solution. Unfortunately the solubility of water in collodion is very low and most of the water you add will precipitate out of the collodion along with the KBr. This is sometimes refered to as a "clearing" process.

Hi John,
Hmm... I'm not a chmist. So do not know about this

But what if I make four parts instead of two:

PART A
250ml Plain U.S.P. Collodion
160ml Ether

PART B
3g Cadmium Bromide
80ml Grain Alcohol

PART C
Slowly mix PART B into PART A and shake after every addition.

PART D
4g Potassium Iodide
80ml Grain Alcohol

Slowly mix PART D into PART C and shake after every addition.

Does this solve problem?

Also I want to say that have already made this mix (with both salts in alcohol) and did not seen any precipitation salts very easily dossolved in alcohol.
May be this woks because I use Cadmium Bromide Tetrahydrate?