Friday, August 16, 2013

Sun Sensitive Paper And Printing Methods

By Cara Torres


Sunlight is often a critical factor for several printing techniques. Sun printing, as it is popularly called, can be done in several methods and with different tools and items, one of them being sun sensitive paper. One common thing they share is the utilization of sunlight as a developing agent or a fixative.

There are many techniques that can possibly be utilized for these processes. One way is the cyanotype. To the unaware, it is otherwise called blueprinting and it is also the most dated non silver photographic process to date. It involves exposing the materials that are being treated with potassium ferricynide solutions as well as ferric ammonium citrate to sunlight, which is used as a source of UV.

Blocking UV light from sensitized material can achieve positive images as well as negative. It will likely retain the image even after a thorough rinsing with water. After it has dried up, the exposed part may turn a particular shade of blue as the remaining parts remain the same color by default.

Another way is to make use of a specialized type of vat dye known as Inkodye. This can be used for this process due to its light sensitive quality. They differ from other vat dyes since they do not make use of oxygen in order to develop the color. Instead, these Inkodyes are developed by the light.

The colorless form, which is originally colorless, will be improved upon when exposed to UV light compared to what it was when suspended in leuco form. As far as usage is concerned, it resembles cyanotype but with some notable differences. Chief among them would be the fact that it can be utilized on textiles and has a full range when it comes to color.

The time it needs to be exposed may vary between three minutes to fifteen. It all depends on what the color is and what intensity level is exhibited by the light. Once it has been exposed, the material must now be washed with both soap and water for the dye to be removed from areas that are unexposed.

There is yet more methods when it comes to sun printing. This one refers to a photographic process that will utilize potassium dichromate. It is known to create a negative plate when it comes to lithographic printing. Films of gelatine will be used in this process and it will be spread over a flat and rigid surface.

Potassium dichromate in dilute solutions can be used for the coating of the surface before it is dried in certain conditions that have low brightness. The treated layer has to be secured and in tight contact, especially with translucent positives as its going to be exposed to the sun for a period of thirty minutes. The potassium dichromate and the light will, at this point, cause the gelatine to tan.

Removing and washing out the untanned gelatine with the use of warm water can allow development for the plate. Once it is dry, on the plate will be the revealed relief print. The surface has the capacity to be inked and then printed should there be a need to produce a mass amount. Sun sensitive paper can be considered just one tool within these various techniques that will require tons of effort.




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