[alt-photo] Re: casein
zphoto at montana.net
Sat Apr 23 14:44:40 GMT 2011
Thanks, Richard, for the link!
Christina Z. Anderson
On Apr 22, 2011, at 5:32 PM, Richard Sullivan wrote:
> Just in case you missed this along the way:
> CASEIN EMULSION.
> BY JOHN BARTLETT.
> HERE is a class of bodies known to the chemist as the protein compounds, two
> of the members of which have recently played a very important part in the
> development of dryplate photography, namely, gelatine and albumen; but there
> is another member whose importance, as far as the writer's knowledge
> extends, seems to have been entirely overlooked, though its analogy to the
> rest of the group might have suggested its employment long ago. The
> comparatively good results which were produced, notwithstanding the careless
> and hap-hazard manner of manipulation, have induced the writer to make the
> facts in the case known to the profession, leaving them to judge of their
> Milk, when subjected to a well-known operation, yields butter and a thin
> watery fluid containing salts and a curdy substance called cheese, which the
> chemist, however, calls casein.
> In a dry state casein is inodorous and of an amber-green color, insipid when
> tasted, possessing neither an acid nor alkaline reaction, putrefying when
> exposed for a long time to the air.
> It combines readily with bases forming compounds, and resembles albumen by
> being precipitated by the metallic salts, and forming with them two
> combinations, namely, one of casein and the acid, and another of casein and
> the metallic oxide. Such are its properties as it occurs in its ordinary
> state of solution in milk, but there is another method of making it, by
> which it is obtained perfectly free from alkali, and by which it possesses
> certain characteristics it does not have in its ordinary condition.
> Ordinary skim milk, freed as far as possible from the traces of cream, which
> persist in spite of the anxious care of the milkman, is coagulated with some
> dilute acid (in the present instance acetic acid was made use of) and the
> whey from the coagulum pressed through aflannel cloth. The cheese thus
> producea is dissolved in a dilute solution of carbonate of soda, and then
> precipitated by hydrochloric acid; the precipitate is repeatedly washed with
> water containing about two per cent, of hydrochloric acid. It is then mixed
> with pure water, in which it swells and gradually dissolves, especially if
> the temperature be slightly raised (about 100°). This solution might be
> called the hydrochlorate of casein, from which the casein may be obtained by
> carefully neutralizing with an alkali. The precipitate must then be washed.
> Casein so formed is but slightly soluble in pure water, but is easily
> soluble in chloride or bromide of ammonium, or in pure ammonia. It is also
> soluble in nitrate of potassa and other neutral alkaline salts. It dissolves
> in dilute mineral acids, but is piecipitated when the acid is in excess. If
> its solution in an alkali he precipitated by hydrochloric acid, the
> hydrochlorate of casein, if we may so call it, is soluble in pure water;
> before dissolving, however, it swells into a jelly-like mass. It was this
> peculiarity which suggested its employment as a substitute for gelatine.
>> From its solution in water it is again precipitated either by a strong acid
> or an alkali. The deposit thrown down by hydrochloric acid swells and
> dissolves in alcohol, but is precipitated again by addition of ether, this
> precipitate being again soluble in water.
> Merely boiling the solutions of casein produces no precipitate. Such are the
> chemical properties of casein. The methods of obtaining it in a soluble
> condition might suggest to the photographer some mode of application in the
> production of emulsions for dry plates.
> The writer not being familiar with the ordinary emulsion practice, made use
> of such combinations as he supposed would produce sensitive surfaces. Having
> neither the leisure nor the skill requisite to the making of a good
> emulsion, he offers these hints to the profession, trusting they may be of
> some value.
> The rapidity with which the plates worked, notwithstanding uneven coating
> and other defects, and the development of the image with the ordinary
> developers, gave promise that something better might result in the hands of
> a skilful and patient investigator.
> A number of different combinations were made, the proportions of chemicals
> varying. With excess of ammonia, however, an increase of sensitiveness was
> always secured, but with a constant tendency to fog when the plate was
> That these few suggestions may fall somewhere on good ground and yield
> abundant harvest is the sincere wish of the writer.
> -----Original Message-----
> From: alt-photo-process-list-bounces at lists.altphotolist.org
> [mailto:alt-photo-process-list-bounces at lists.altphotolist.org] On Behalf Of
> Christina Anderson
> Sent: Friday, April 22, 2011 2:35 PM
> To: The alternative photographic processes mailing list
> Subject: [alt-photo] Re: casein
> Not sure about answers to your questions; maybe Peter Blackburn will know.
> However, from experience, it is quicker with everything so I don't mess
> around...I have coated, dried on cool with a hair dryer and exposed
> immediately. But I have also done 8 at once and thus the last one definitely
> sits over 1/2 hour.
> Christina Z. Anderson
> On Apr 22, 2011, at 1:37 PM, Marek Matusz wrote:
>> THenks for kind words. I will not put those first prints on display,
> although I saved one. ANother question. How long does the sensitized
> solution keep?
>> ANd another one: how fast is the dark reaction?
>> P>S> I am on the second set of prints now... exposing
>>> From: zphoto at montana.net
>>> Date: Fri, 22 Apr 2011 13:23:02 -0600
>>> To: alt-photo-process-list at lists.altphotolist.org
>>> Subject: [alt-photo] Re: casein
>>> I will scan my very first set of casein prints and put them in the same
> URL location shortly and you will see there is hope between those first
> prints and the ones I have in the Past Lives on my website.
>>> Christina Z. Anderson
>>> On Apr 22, 2011, at 1:14 PM, Marek Matusz wrote:
>>>> My casein pwoder came a few days ago and I gave it a try. I mixed it
> with a amonim carbonate solution, It mixed very well with just a spoon, no
> mixers. It has been sitting on the counter for 2 days, actually today is a
> third day and I have not noticed any viscosity changes. It looks exactly as
> I have mixed it fresh. My first attempt in printing was a disaster. I have
> not made anything that bad in a long time. Looking at it I think I
> overloaded it with black pigment. It looked so dark and beautiful when
> brushing. Unfortunatly it mostly flaked out leaving a horrible stain and
> traces of the image.
>>>> I am going to try with watercolour pigments and a lower load, perhaps
> similar to gum
>>>> Not discourage just curious.
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