Re: Please complete this tintype formula for me:

Jon asked about tintype:

> Sensitizer: Silver nitrate (what dilution?)
> Developer: ???
> Stop: Water (2 baths?)
> Fix: Potassium Cyanide (4%?)
> Varnish: (???)
>
> What is the process of plate preparation (I've read they should be painted
> black first and then sensitized?) and what metal is best to use?
>
> Thanks,
> Jon

I haven't seen the Nat Geo site, but judging from the silver nitrate dip
and the cyanide developer it appears that you are doing real collodion
tintypes. Excellent!

Plates are usually thin steel (0.010"-0.030") that have either been dipped
in asphalt (roofing tar) thinned in mineral spirits, drained, then baked,
or dipped in black lacquer, drained, and then baked.

A 9-12% silver nitrate solution will work fine. The developer should be a
solution of ferrous sulfate (sulphate if you're in Great Britain) with a
bit of acetic acid added. You use just enough to cover plate. Only this
inorganic developer makes the proper silvery-white silver deposits that
ambrotypes and tintypes require. If you're a slow exposer, a bit of
alcohol in the developer will re-soften the collodion and allow better
penetration. I generally use a running water rinse followed by a distilled
water bath. Potassium Cyanide works OK at 1% (see the site link below),
although 2-5% is more common. You need a good rinse after fixing,
finishing with distilled water again. Traditionally, sanderac varnish (gum
sanderac in alcohol) is used. I have also used both shellac and clear spar
varnish with good results. Collodion is tough once it is dry, so, pretty
much anything will work. The varnish is poured on and run around, then
drained off a corner, just like coating the plate.

Here is a page with typical ambrotype formulae:

   http://www.companyphotographer.com/html/formulas.html

I recommend the rest of his site, as well.

Best regards,

etienne
Received on Fri Jul 23 20:54:43 2004