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  1. #1
    Mustafa Umut Sarac's Avatar
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    Most durable photograph recording medium : Photosensitive Glass

    Invented at 1937 and used by american intelligence. Not sunglass technology , totally different.

    One of the best written wikipedia article, I am starting with wikipedia article than Corning Glass Patents, after them I will put some commercial photosensitive glass articles .

    This technology is not sensitive to visible radiation , is not sunglass technology and medium must be protected from daylight uv radiation and after uv exposure , it must be heated within furnace 1000 F degrees for 4 hours. You can print three dimensional images inside of glass.

    If glass does not break , nothing happens to print for millions of years.

    There is a great wiki article.
    ------------------------------------------------------------------------------------------------------------------------------
    Photosensitive glass is a crystal-clear glass that belongs to the lithium-silicate family of glasses, in which an image of a mask can be captured by microscopic metallic particles in the glass when it is exposed to short wave radiations such as ultraviolet light. Photosensitive glass was first discovered by S. Donald Stookey in 1937
    History

    Photosensitive glass was invented in November 1937 by Dr. Donald Stookey of the Corning Glass Works. It was not announced publicly until ten years later on June 1, 1947.It was officially patented in 1950 by Stookey as U.S. Pat. No. 2,515,937 and U.S. Pat. Nos. 2,515,943 with gold microscopic particles.

    Exposure process

    When the glass is exposed to UV light in the wavelength range 280–320 nm, a latent image is formed, the glass stays transparent after this stage, however. the only difference that occurs is that the absorption of the glass increases in the uv range of the spectrum, this absorption increase is only detectable using uv transmission spectroscopy. The reason behind this is suggested to be an oxidation reduction reaction that occurs inside the glass during exposure in which cerium ions are oxidized to a more stable state and silver ions are reduced to silver.

    Post-Exposure Heat Treatment

    When the glass is heated to temperatures in the range 550–560 °C for several hours the latent image is converted to a visible image through photoexcitation.Exposure through photographic negatives permits the development of three dimensional color images and photographs. This heat treatment is done in two stages: the temperature is first raised to about 500 °C to allow for the completion of the oxidation-reduction reaction, and formation of silver nanoclusters. In the following stage, when the temperature is raised to 550–560 °C, a new material (lithium metasilicate) with the fomula (Li2SiO3) forms on the silver nanoclustors, this material forms in the crystalline phase.

    HF Chemical Etching

    The lithium metasilicate that forms in the exposed regions of the glass has the unique property of being strongly etched in hydrofluoric Acid (HF). Hence allowing a three-dimensional image of the mask to be produced, the resulting glass microstructures have a surface roughness in the range 5 μm to 0.7 μm.
    [edit]
    Applications

    Photosensitive glass

    Spinfex photosensitive glass

    Photosensitive glass is used in printing and reproducing processes.Photosensitive glass is like traditional camera film except that it reacts to ultraviolet (UV) light, where camera film responds to visible light. The ideal wavelength to use for exposure should be between 300 and 350 nm, with 320 nm being optimum.

    Photosensitive glass contains microscopic metallic particles.These microscopic metallic ion nanoparticles are made of gold or silver which is responsible for the refractive index change. Photosensitive glass is similar to photographic film. Photographic film uses chemicals, while photosensitive glass uses gold or silver ions in the material that will respond to the action of light.[7] The process is to pass light of the ultraviolet wavelength through a negative on the glass. Photographic resolution can be obtained with adhesive polyester as a reverse negative, however anything which resists UV light can act as a "negative."

    The glass is sensitive to light that when passes through a mask can ultimately turn it into a permanent picture with a heat process "fixing" permanently the image. Silver glass "latent images" will develop in 3–4 hours at 886–976 °F.Gold glass "latent images" require a higher temperature of 968–1058 °F and over a similar period of time for postbaking.Postbaking hastens the occurrence of the particles with the shadow areas of the negative, permitting deeper penetration into the glass than the highlighted areas. This gives the picture three dimensions and color.

    The photograph is developed by heating the photosensitive glass around 1000 °F for several hours after exposure. The glass itself is photosensitive and produces a three dimensional image. Particles that are invisible to the naked eye (i.e. gold or silver) are in the glass. These microscopic particles move and grow when heated to form the photographic image itself. The process is similar to camera film, however a "negative" is placed on top of the photosensitive glass and then exposed to ‘’’ultraviolet’’’ light. Camera film, of course, would be exposed to ordinary visible light. Then there is a special process for the exposed photosensitive glass. The glass is reheated then in a kiln and postbaked for several hours. The image then "appears" within the special exposed glass as if by magic. The heated piece of photosensitive glass is then allowed to cool down and the process is done. The positive images produced within photosensitive glass comes in a variety of colors.

    As a material for the hot glass studio artist, an additional method of producing imagery in an object using photosensitive glass is to first blow an extremely thin rondel (cased or otherwise) which is annealed in the typical manner. That rondel is then cut into sections which are exposed under a negative. Next, those sections (containing the latent image) are warmed and applied to the surface of a gather of hot glass on the blowpipe. As the object is completed over several furnace reheats, the heat develops the image as the object is being created. This method specifically eliminates the need for the reheating of the object in a kiln for development, which consumes considerable oven time, energy, and the risk of loss or damage due to shattering on the way up to temperature, or more importantly, slumping while being held at temperature. The timing of the glassblower determines the final degree of development, and simple choices of form minimize distortion in the image.

    Since the image is inside and actually a part of the glass itself, photosensitive glass is the most durable photographic medium known. It is claimed that a photo image within photosensitive glass is the most durable form of photography and will last as long as the glass itself. The photographic image is not on the surface of the glass, but internally

    Fluorescent photosensitive glass makes it possible to make fluorescent photographs and fluorescence holography

    Photosensitive glass is different than photochromatic glass. Photochromatic glass is used in self-darkening sunglasses which darkens when exposed to bright daylight. It then returns to see-through transparency when strong daylight is removed and can then be used indoors as regular glasses.

    Little has been done to develop the product since its patent.It is labor intensive and has a high cost.[2] Only large commercial glass factories produce it. In the 1980s photosensitive glass was created to a small degree to be used in "hot glass" work.Then individual artists owned smaller studios and created works in blown glass and began experimenting with photosensitive glass. Going into the Twenty-First Century only a few glass artists know the technique of achieving good results with photosensitive glass. In the present time, the only photosensitive glasses produced are Foturan and APEX. Foturan os profuced by Schott Corporation and APEX by Life Bioscience. Photosensitive glass has been used as a holographic material to record diffractive optical elements for high power laser applications.

    Military applications

    One of the reasons between the time photosensitive glass was invented and the delay why it was announced approximately ten years later to the public is because of its military applications.It is possible to burn images and words that are hidden in photosensitive glass until heated at a high temperature.The military used this fact during World War II to send secret messages to allied troops in pieces of what looked like "ordinary glass. At the other hand, the person who received the "ordinary glass" just had to heat it up to read the hidden message. Because of this application photosensitive glass was kept secret until the end of World War II.
    Building applications

    The United Nations Building is faced with hundreds of square feet of photosensitive glass.

  2. #2
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    U.S. Pat. No. 2,515,937 page 1

    paper 1 attached 2515937
    Attached Thumbnails Attached Thumbnails patents 11.jpg  

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    U.S. Pat. No. 2,515,937 page 2

    page 2 U.S. Pat. No. 2,515,937
    Attached Thumbnails Attached Thumbnails patent 12.jpg  

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    U.S. Pat. No. 2,515,937 page 3

    U.S. Pat. No. 2,515,937 page 3
    Attached Thumbnails Attached Thumbnails patent 13.jpg  

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    U.S. Pat. No. 2,515,937 page 4

    U.S. Pat. No. 2,515,937 page 4
    Attached Thumbnails Attached Thumbnails 14.jpg  

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    U.S. Pat. No. 2,515,937 page 5

    U.S. Pat. No. 2,515,937 page 5
    Attached Thumbnails Attached Thumbnails 15.jpg  

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    Gaffer® Photosensitive Glasses

    For the first time, Gaffer Coloured Glass offers photosensitive glasses suitable for use as a casing glass for the studio glassblower. Although noble metal photosensitive glasses were developed by Dalton and later Stookey, at Corning, during the Second World War (and kept under wraps by the US government until the war ended), they were never much exploited by Corning. They offered them largely as a novelty glass in the 1950’s and 60’s.

    Gaffer Glass has reworked the original recipes, in order that the glasses will be compatible with typical soda lime glasses used by the studio artist. Particular attention has been paid to aligning the properties of expansion, viscosity and durability.

    Properties and Application
    Gaffer photosensitive glasses can be used in the same way as any other casing glass, either as an inner or outer casing, or as an interlayer. They are soft, and easily worked. In order to exploit their properties, however, these glasses must be able to be exposed to ultraviolet light in the finished piece. Think of the glass rod as virtually like filmstock. It must be kept in the tube we supply until ready to use for blowing. After finishing a blown piece, that also must be kept in the dark until it is ready to be masked and then exposed and developed.

    Although photosensitive glasses are not anywhere near as sensitive as film, the ambient levels of UV light in a room will still be sufficient to “spoil” the glass after a day or two. Avoid direct sunlight. A “spoiled” glass, however, simply becomes an ordinary gold ruby or silver yellow, on being reheated, so is not completely wasted.

    Exposure
    The exposure of photosensitive glass is in many respects similar to that of ordinary photographic material. It differs mainly in the fact that exposure requires UV radiation, and usually requires considerably more time. The wavelength of light required is important, being between 300-350nm, and preferably peaking at 320nm. Sunlight can work, particularly at sunburn strength, but the results are variable. More consistent results are obtained by the use of commonly available fluorescent suntan tubes. Philips TLK 40W/10R low pressure mercury vapour fluorescent tubes are ideal. They are available in 600mm (2 foot) lengths. Other suntan tubes offer similar specifications. They should all be branded UV-A.

    Note: Not all UV lamps are the same. Some lamps for instance, used for curing silk screening dyes or photo printing etc. may have the wrong wavelength for this application. Exposure at a distance of 100-150mm (4-6 in) for about 20-40 minutes is sufficient for most effects. An even exposure of a vessel can be achieved with an old record turntable. With the gold ruby glass, short exposures will give blue through to purples; longer exposures will give a true ruby. Increasing exposure with silver based glasses results in an increasingly deeper and stronger yellow colouration. The colours produced, and the density of the hue, depend on exposure time and intensity, but importantly, also on development temperature, and time. After UV exposure, only a “latent image” results, which is not visible. Development by heat is still required.

    UV Resists.
    Anything which resists UV light can act as a resist or negative. For photographic resolution the most efficient material is adhesive polyester as a reverse negative, available from specialist photographic suppliers. However, anything which can stop UV is suitable. Felt tip pens, Letratone, bromides, masking tape etc. are all effective to varying degrees.

    Development
    Unlike ordinary film, which requires chemicals to develop the image, photosensitive glasses simply require heat. For silver glasses the “latent image” will develop in 3-4 hours at 475-525oC (886-976oF)
    For the ruby glass a higher temperature of 520-575oC (968-1058oF) is required over a similar period of time. The higher the temperature, the quicker the development. The term “latent image”, refers to the fact that simply exposing the glass to UV light will not make visible the colour. The colour centers are “latent” until developed by heat. If the glass is slumping, then simply lower the temperature, and take more time for the image to develop. Only by heating to the correct temperature range, for long enough, will the latent image reveal itself or strike.

    As with exposure, short heating times, and low temperatures, will produce blues and purples with the gold ruby: high temperatures for longer periods promote the true ruby shade. The silver yellow deepens in hue with long exposure and development.

  8. #8
    Mainecoonmaniac's Avatar
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    I remember 30 years ago there was a glass product that you can make negative masks out of it. If I remember correctly, you would use high intensity light to expose the glass and an image would be created for the mask. The glass then can be cleared with hot water to be reused again. Does anybody remember such a product?
    "Photography, like surfing, is an infinite process, a constantly evolving exploration of life."
    Aaron Chang

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    Foturan Photosensitive Glass

    Foturan is a photostructurable glass ceramic (PSGC) manufactured by Schott Glass Corp and distributed by Invenios. Foturan is used as a MEMS and MOEMS substrate. Microfabrication in Foturan is achieved through patterning by a pulsed UV laser, a follow-up heat treatment step, and chemical etching. In Foturan, the exposed areas experience a selective phase change in which the native amorphous glass phase converts to a crystalline lithium silicate phase. The degree and type of crystallization are both responsive functions of the irradiation and thermal processing procedures. Under high exposure, the crystallized areas etch up to 30 times faster than the unexposed material in HF, with the etch rate varying with irradiation dose. Because Foturan is transparent at visible through IR wavelengths, direct-write XYZ exposure with a pulsed laser can detail complex 3-D structures within the Foturan material. Devices made from Foturan may be glass, a glass-ceramic composite, or ceramic, with the final material composition depending on the irradiation and thermal processing procedures. Excellent aspect ratios (>30:1) have already been demonstrated in Foturan.

    At Invenios we make 3-D MEMS structures by implementing cost-effective manufacturing solutions that produce consistent results with a resolution measured in microns.

    Invenios Foturan Resource Guide: Selected Articles about Photostructurable Glass-Ceramics

    2004 Direct ultrafast laser writing of buried waveguides in Foturan glass Stephen Ho and Peter R. Herman, Ya Cheng, Koji Sugioka, and Katsumi Midorikawa


    2002 3D microstructuring inside Foturan glass by femtosecond laser Ya Cheng, Koji Sugioka, Masashi Masuda, Koichi Toyoda,Masako Kawachi,
    Kazuhiko Shihoyama, and Katsumi Midorikawa


    2005 Holography in commercially available photoetchable glasses Michael Kösters, Hung-Te Hsieh, Demetri Psaltis, and Karsten Buse


    2006 Integrating 3D photonics and microfluidics using ultrashort laser pulses Ya Cheng, Koji Sugioka, Katsumi Midorikawa, and Zhizhan Xu

  10. #10
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    http://glassmusings.blogspot.com/201...ive-glass.html

    Photosensitive Glass
    Here is a picture of an interesting process involving hot glass (blown) work. This could also apply to fused glass work although I haven't tried it.
    Attachment 58553

    Attachment 58554


    This piece is a blown platter that is about 16" in diameter. The intent was to blow a rondel, a round platter that doesn't really have any dips in the center and almost perfectly flat. That is one of the ways they made window glass in the "good old days". Anyway, this one is pretty good for me. There is a slight depression in the middle which is about half an inch deep. The interesting part of this is that you use a special glass color which is clear, but photosensitive. Thus it does need to be kept in a special wrapper until you are ready to use it. You blow the blank and then anneal/cool it. The annealer shouldn't be opened much as the piece is light sensitive and will pick up some darkening, however it is a very large exposure time.



    The photo above shows the blank after it came out of the annealer and ready for its exposure. I took a bunch of egyptian symbols as well as a photo of me and a colleague on horses at the Great Pyramids at Giza. I just taped these on the glass and even used a Sharpie to write my name and date on it. We had to work in a dark room with a safe light, just like old fashioned black and white photographic dark rooms.

    This was then taken outside. A very strong ultraviolet light, the sun being a great source is needed to expose the blank, just like a photograph. We left it outside at high noon for 45 minutes as there was some brief clouds. Normally 30 minutes in bright sun should be sufficient.

    This is then placed in a cold annealer, brought slowly up to working temperature (around 1100 degrees), and then annealed again. This sets the image on the blank. You can see in the top picture the color difference. There is an interesting color cast to the developed image and overall blank. The original blank was a very pale blue, and this developed piece is a medium amber color. It would take a lot of practice to figure out just how to make use of the coloring.

    Overall, I was impressed with the detail you can obtain using this process. I don't think I'll do it a lot, as it does require special glass and a means to expose it, but it sure is fun to contemplate.

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