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John McKean

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Making your own Plates

John McKean delivered a lecture to the Edinburgh Photographic Society on 7 June 1882, entitled:

      The Modern Photographer - his Power and Appliances.

[BJP:  1882, p.358]

John McKean appreciated the progress that had been made in photography.  He said:

"Amongst the mysterious orbs of heaven and the rolling clouds, from Alpine heights to the deepest caverns of the earth, the camera is capable of revealing to the eye of man a  mighty store of knowledge ...

... we owe a deep debt of gratitude to those noble pioneers of the art who have placed in our hands such a marvelous power in so simple a form as that of the gelatine dry plate."

Yet he regretted the fact that so few had mastered the process of making such a plate.  He encouraged photographers to make their own plates, saying:  

"I intend this evening to give you a practical demonstration of my mode of working; and I venture to say that after two years' work without a negative bath, and daily using my own plates, there is no reasonable excuse for even the humblest of the  profession not to become their own plate-makers.   ...   ...

Two bottles, a bowl and jam pot contain the simple ingredients for the production of ten ounces of emulsion.

In the first bottle we have -

Silver nitrate 200 grains
Distilled water 1 1/2 ounce

In the second bottle we have -

Ammonia bromide 105 grains
Ammonia chloride 5 grains
Ammonia liquor (880) 6 drops
Water 1 1/2 ounce

The jam pot contains -

Gelatine (Nelson's No 2) 40 grains
Potassium Iodide 5 grains

Water

1 1/2 ounce"

John McKean went on to describe his process:

" -  We now place in the bowl half an ounce of gelatine.  (I use equal proportions of German and Nelson's No 2.), and, covering it with water leave it to swell till we have mixed and digested the emulsion which we will now proceed to do.

  -  Placing our two bottles and jam pot with their contents in a pan of sufficient size, along with an ordinary bath thermometer and a little water, we raise the temperature to 140 degrees Farh. over a fire or Bunsen burner, and, shutting out all actinic light from the room, we take in our hand the bottle containing silver nitrate, and in the other a glass rod - glass or silver spoon. 

... I prefer a horn spoon ...   ...   we begin by using the handle to agitate the solution of gelatine and iodide.

-  We next introduce in a gentle stream our solution of silver nitrate a la Captain Abney.  

-  We have now our old friend the iodide of silver in contact with our new love, gelatine though they do not seem quite to agree with each other, the iodide clinging to the handle of the spoon as if anxious to avoid the hot treatment to which it shall shortly be subjected; but immediately we introduce the solution of bromide and chloride harmony is restored.

-  Our emulsion is now in the first stage of sensibility, and may, after a thorough wash and addition of the rest of the gelatine, be considered in its infancy, capable of receiving impressions of the outward world, though a little too slow for these days of spring shutters and photographic revolvers.

-  We have, however, a simple and effectual means of adding this desirable degree of sensitiveness, namely the process on boiling.  Before doing so, it is well to withdraw a few drops of our emulsion, and spreading them on a glass plate, we may by transmitted light mark the difference between its youthful bloom before and its grey maturity after boiling.

-  So far we have accomplished our task of making what we would term a modern emulsion.  We will now cover with a lid the dish containing it, round which I place a cloth to keep it from coming in contact with the sides of the pan in which we intend boiling it.

-  Covering all with the lid of a pan, and re-lighting our Bunsen burner ... leave it to "cook" as long as in the present occasion we may find it convenient.  I usually allow it thirty minutes."

John McKean added:

"Meanwhile, let me ask if there is anything so far as we have gone to debar anyone with moderate intelligence from the independent position of having at his demand not only as quick plates and reliable as any in the market, but plates suitable for all circumstances?

As the pot continued to boil, he said:

"... Thus far it may be said the process is easy and clearly understood; but our task is not yet done, nor is the contents of the pot sufficiently cooked.  So to sharpen your appetites till that is ready I will say a little on ...   ... a quick and ready means for drying your plates after they are coated   ...   ... I plied the tools to the formation of the drying cupboard now here before you.   ...   ...   I usually coat my plates after business hours and they are ready for use the next morning ...  .

-  Previous to stopping the boiling operation we shall drain the water from the bowl of gelatine, and, turning out the gas under the pot, withdraw the dish of cooked emulsion and replace it with the bowl.

-  After stirring the emulsion for a little we shall examine a few drops through a glass plate, and comparing it with the first, we find it has changed from an orange to a grey-blue colour - a change which I do not pretend to explain.  It is enough for out purpose to know that it has become more sensitive to light, and in this state I decant it right into the bowl, and in a few minutes the gelatine is dissolved.

-  I now leave it to "set" all night, and in the morning squeeze it through coarse canvas into a can of water, over which I tie a piece of the finest material.  At the bottom of the can is drilled a small hole, through which is passed a rubber tube, forming the simplest and cheapest washing apparatus yet invented.  ...  ..."

And finally, coating the plates:

"We now begin the operation of coating the plates by getting everything in position.

-  In our pan filled with hot water, place a bowl, in which the emulsion is transferred from the washing apparatus when it will quickly be dissolved

-  Over a second bowl I stretch two plies of fine cotton, through which I filter the emulsion, and it is ready for use.  For this operation the only addition to our appliances will be two levelling stands and two plates of thick glass.  Placing one on the table at the left and the other within arm's length of the cupboard, with the horn spoon in hand proceed.

-  ...   The spoon contains perhaps three times the emulsion necessary to cover the quarter-plate in my hand; but pour it all on, and you need no glass rod to conduct it to the edges of the plate;  then pour off the surplus into the spoon, and return it to the bowl.

-  ...   go on with another   ...  ...  By this time the first plates will be thoroughly "set" and may be placed in the cupboard.   ...   ... 

Satisfaction:

Thereafter you may return to rest with the satisfaction of knowing that a batch of cheap and reliable plates will be ready for the first sitter in the morning."

John McKean

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