------- Forwarded Message
Date: Thu, 29 Feb 1996 15:51:53 -0700 (MST)
From: John Rudiak <wizard@laplaza.taos.nm.us>
To: alt-photo-process@vast.unsw.edu.au
> Date: Thu, 29 Feb 1996 08:58:44 -0700 (MST)
> From: John Rudiak <wizard@laplaza.taos.nm.us>
> To: alt-photo-process@vast.unsw.edu.au
> Cc: Multiple recipients of list <alt-photo-process@vast.unsw.edu.au>
> Subject: Re: Chrysotypes & Gold prints
> In-Reply-To: <31367194@smtp.nla.gov.au>
> The problem with trying to print in gold salts prior to Mike
Ware's
> development of the new Chrysotype process was the tendency of the gold to
> precipitate out of solution when a sensitizer was mixed using the
> traditional photoreactive compounds, such as ferric oxalate, et. al. It
> seems that the "crux of the biscuit" in this process is the introduction
> of a suitable ligand to hang onto the gold and keep it solution long
> enough for it to be coated and dried. Without a more complicated
> description, this ligand is 3,3'-thiodipropionic acid, available from
> Lancaster Chemicals in Windham, NH. Mike, who seems to be a fan of
> ammonia based systems has chosen ferric ammonium oxalate as the light
> sensitive iron compound, available here from Spectrum chemicals.
>
> The sensitizer can be compounded into three separate components which are
> mixed in equal amounts before coating onto the paper. I used to use
> gallery 100 with beautiful results, until they (Rising) decided to remove
> 80% of the sizing. Haven't tried Platine yet, but assume it will work
> well.
>
> Part A of the sensitizer is the gold compound and is made by taking 0.9M
> gold chloride (35.4%) and adding to it slowly (there is a heat build up)
> an equal amount of 0.9M sodium hydroxide (36%)
>
> Part B is the ligand, and is a 1.25M solution. (22.3gm. in 100ml water)
because we need the disodium salt, take 100ml. water, add 9 gm. sodium
hydroxide, COOL, then add 20 gm. of the TDPA>
> Part C is the ferric ammonium oxalate, in a 0.45M concentration which
> works out to 19.3 gm. in 100ml. water.
>
> These will hold up very well when kept separate, the least stable being
> the FAO which seems to last a couple of months in solution.
>
> The exposure is very similar in duration and wavelength requirements to
> Pt/Pd.
>
> After eeposure, the print is developed in a 1% solution of either
> tartaric, citric, or oxalic acid, or even EDTA, tetrasodium salt. Do not
> reuse developer
>
> Clear for a couple minutes each in 5% EDTA, Kodak Hypo Clear, and the
> another EDTA. Wash.
>
> The process is very sensitive to humidity of the coated paper- changing
> the colors of the print due to the different size particles of colloidal
> gold deposited on the paper fibers. I have some prints which show a
> split- blue highlights with burgundy shadows.
>
> The paper choice and developer choice also affect colors, but i have not
> had enough time to explore all the possibilities.
>
> Good luck, please feel free to ask for more info, I am preparing a more
> detailed article on this process (Any publishers out there?) and it
> woul;d be good to hear what any other questions might be.
>
> This should be enough to get you started.
>
> Oh yeah, the mixed sensitizer will last for 1/2 hour or so, depending on
> conditions. I Mixed 10ml. the first time and came back the next day to a
> bottle, the interior of which was coated with a layer of pure gold.
>
> Later,
>
> John Rudiak
>
------- End of Forwarded Message