[alt-photo] Re: casein history

Evan J Hughes evan at evanhughes.org
Fri Jul 20 18:42:00 GMT 2012

Hi Chris,

    Very many thanks for the extract of the patent; I will try with 
alkaline developing baths.   I have found carbon tissue is most 
susceptible to melting/ over softening when the tissue is being 
sensitised or mated to the final support; I use spirit sensitising now 
so do not have many issues, however I could see that tray sensitising 
could be quite alarming if the tissue started to dissolve in the 
dichromate bath.

    Did the patent mention what the tissue temporary support material 
was intended to be?    I use a paper support but I vaguely recollect 
some of the early patents consider using a thin layer of colloid.  With 
the colloid, it may be possible to expose from the reverse side, through 
the colloid support, so that the image can be developed directly (i.e. 
the unhardened gelatine is on the opposite side to the colloid support 
film).  A transfer could then be made to the final image paper and the 
colloid layer removed.  If this is the case, the tissue does not have to 
separate from its temporary support during the developing.  When the 
tissue is poured onto a paper backing, the gelatine does need to melt in 
the developing bath so that the backing paper can be removed and the 
development completed.   I am intrigued to see how the alkaline bath can 
penetrate well enough through the paper to the unhardened 
gelatine/casein mix in order to allow it to dissolve enough for the 
support paper to be stripped away; I will give it a go though.

    I also noticed the patent says 'Soap, however, is not absolutely 
necessary'.   I use a soap-based glop, but I add soap not for pliability 
(the sugar does that), but to remove the bubbles (yes it is counter 
intuitive!).   Does the recipe also use sugar for pliability?

   Best regards,


On 20/07/2012 01:28, Christina Anderson wrote:
> Hi Evan,
> Glad you are trying this! Gelatin was susceptible to melting in hot water or weather and casein would help with that, esp. in summer months. Here is part of the patent description that may be of some help.
> My third improvement consists in replacing the gelatine and its analogues in the above compounds wholly or in part by certain other organic compounds having the property of insolubility in warm water but of solubility in some other chemical agent, such as ammonia or the alkalies or salts; and the best substances I am at present acquainted with are the proteine compounds which possess the specified properties, such as caseine, legumine, modified albumen, and their congeners. A pigment compound so formed, and mixed with a bichromate, is sensitive to light; but the picture is not revealed or developed by hot water until a few drops of ammonia or other alkali possessing the like property has been added to the water. In carrying out this part of my invention I form a curd of skimmed milk, as in making cheese, by precipitating the caseine with rennet or by an acid. I collect the curd on a filter, and, after partially drying it by pressure, I dissolve the caseine or curd in dilute liquor ammonia. This solution—which should be as thick as the previously described solution of gelatine in four and a half parts of water—I use instead of a portion of the gelatine solution; that is to say, I take away part of the gelatine solution and substitute in lieu thereof an equal portion of the caseine solution. The quantity so substituted may be greatly varied. Ten per cent of the caseine solution so substituted renders the resulting compound insoluble in water until a certain quantity of ammonia has been added, and twice or three times that quantity does not prevent a workable tissue compound being formed; and in making such a pigment compound I find it best to mix the caseine solution with that of the soap, and add the two together to the gelatine. Soap, however, is not absolutely necessary, as the caseine itself gives flexibility to the tissue, and thus supersedes the necessity of employing the soap...
> Christina Z. Anderson
> christinaZanderson.com

> On Jul 19, 2012, at 11:30 AM, Evan J Hughes wrote:
>> Hi Chris,
>>    I hope to have another go at adding casein to carbon tissue over the next few weeks, but on thinking about the behaviour of casein, do you know what the advantage of adding casein to carbon tissue was thought to be?
>>    My first thought was that it may make the tissue more sensitive and therefore expose faster, but otherwise, many of the properties of casein are not necessarily an advantage, i.e. it is important to have a recipe that develops easily in warm rather than hot water to reduce issues with bubbling; the unexposed tissue needs to melt very easily to allow the support paper to be stripped away.   I do not see how the casein may help with adhesion during transfer, although it can make a very effective glue.
>>   I plan to try a few glop mixes ranging over 10% to 30% of casein; have you noticed how much pigment was used in the gelatine-casein carbon tissues?   I wonder if the pigment quantity may be very high so that a very thin, high contrast tissue can be poured; rapid automated manufacture is then much more simple which would be important for mass-produced tissue.
>>      Best regards,
>>            Evan


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