[alt-photo] Re: casein
richsul at earthlink.net
Fri Apr 22 23:32:35 GMT 2011
Just in case you missed this along the way:
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
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.
From: alt-photo-process-list-bounces at lists.altphotolist.org
[mailto:alt-photo-process-list-bounces at lists.altphotolist.org] On Behalf Of
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
> 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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