OT: Poor Boy Collodion recipe

[phuphuphnik]

Anyone have the recipe for a collodion wet plate that uses Potassium Bromide and Potassium Iodide instead of the cadmium? I found it once, but lost most of it.

cheers,

chriso

[photolytic]

Boy are you one the wrong forum!!!

Try looking on http://www.cwreenactors.com/phorum/list.php?

You’re belching mercury and bromine out of your fume hood and you’re worried about a few 10ths of a gram of cadmium salts in your collodion which will end up in your also toxic silver nitrate bath? I hesitate to ask if you fix your wet plates with potassium cyanide.

First of all potassium bromide is COMPLETELY INSOLUBLE in the alcohol/ether solvent of collodion.

Second. If you have any potassium iodide in your collodion and you add any soluble bromide salt, such as ammonium bromide, to your collodion, it will instantly equilibrate (They called that double decomposition in the old days) to a mixture containing potassium bromide which will begin to precipitate.

KI + (NH4)Br <—> KBr + (NH4)I

AS the KBr begins to precipitate, the equilibrium in the above reaction will try to maintain a the concentration of KBR in solution by shifting the reaction to produce more KBr until the reaction runs out of either potassium or bromide leaving nothing but iodide in the collodion.

Some will tell you to add water to the collodion formula to prevent this precipitation but water too is insoluble in ether and will leave the collodion with a hazy of suspended aqueous KBr solution. After week or so that too settles out (They call it “clearing), leaving the collodion clear but with little or no bromide.

http://www.moderndags.com/DSCN3674.jpg

If you still don’t want to use cadmium salts, which are soluble in alcohol. Your best bet is to use replace all of the potassium iodide/bromide salts with those of non-toxic sodium, ammonium, or lithium (cures you of bipolar disorder too). For examples, see the excellent NaI/NaBr wet plates posted by “Sean”) in the collodion forum above.

You would also help yourself by consulting the excellent collodion advice of longtime collodion and daguerreian expert George Berkhofer.

I made my first wet plates in 1955 and, with the help of my friend George Berkhofer, developed all of my collodion formulae with nothing more than a high school chemistry background so it’s not rocket science.

I can vouch for the excellence of many of the collodion formulas to be found in the Towler’s Silver Sunbeam” and Carey Lea’s “Manual of Photography” or Hardwich’s “A Manual Of Photographic Chemistry”, all of which can be found on-line or as reprints on eBay.

[phuphuphnik]

Actually, I was looking to avoid the additional ether. If I used cyanide, then silver plating my dag plates would be better as well. I am waiting to be authorized to post on the forum you suggested, in the mean time I know many here have done wet plate as well, so I asked. Thanks for the chem instruction, I was having difficulty following why it took so long to clear. I also can’t find cadmium iodide. The formulary has the bromide.

cheers,

chriso

[photolytic]

You mentioned only the cadmium salts in your post so I didn’t give ether advice.

No need to add extra ether.

We never did in the past and several on the forum also agree.

Commercial Collodion already comes dissolved in a 75/25 ether/alcohol solvent.

Just dilute the collodion 50/50 with alcohol. Add up to 60/40 in winter, when the temp is low.

Don’t bother buying Everclear 95% potable alcohol at >$10 a bottle too unless you’re going to drink it. Denatured from Menards is much cheaper ($15/gal) and works just as well if not better.

Artcraftchemicals.com has both Cadmium Iodide and Bromide at approx. $25/oz.

You can even request Potassium cyanide although they don’t list it in their catalog.

[phuphuphnik]

Fantastic!

Cheers,

chriso

[Author]

Posts