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.  

 

 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.

Photos on Glass - Something Old, Something New

When the first photographs were made in the 1840's and for quite some time thereafter, they were "printed" on pieces of glass. The first type, called daguerreotypes were actually done on a mirrored glass surface treated with a light sensitive chemical solution. Of course with the invention of printing on paper, photos on glass died out. Paper was cheaper, much more portable, and not as easily broken as the glass. Well, things old become new again in slightly different forms.



The image of a glass plate shown to the left here is one example of the old but new again idea of printing photos on glass. However here the photo is actually "in the glass". Gaffer Glass makes a photosensitive glass rod that can be blown into any shape and then exposed to a negative, developed, and set in a most unique way. For those interested in the deeper technical aspects of using this glass, refer to the link above to read the details on Gaffer's site.



The process is pretty straightforward. The hardest part is blowing the blank. The rod is picked up and then encased the usual way. Here I used an opaque amber color. The base photosensitive glass is transparent and has an interesting tonal range. You are never going to get "Kodachrome" quality, but the effects are interesting. Picking the right backing color is important. I also created on in a deep blue thinking the hues would be complimentary. In fact, you have to look very close to see anything in that piece.



I'm not great at blowing rondels, a large round flattish glass blank. This is the same process as very old window glass was made. This piece is actually quite round, a first I think for me, and about 16" in diameter. The only unfortunate part is there is a slight dip in the center making this more like a large plate than a nice flat rondel. While annealing the blank needs to be kept in the dark and well covered until ready for exposure. It is actually UV light that exposes the image so some light is OK, but not for very long.



I created a bunch of negatives in Photoshop and printed them out on transparency film. That is me on a camel in front of the great pyramid in Egypt (but that's another story). I cut these into pieces as it was hard to get perfectly flat due to the shape of the blank. This is done in a dark room with photographic safe light. I then put the blank in direct sunlight for 30 minutes. Then the exposed blank was put into a cold annealer and brought up to about 1000 degrees and held for about 4 hours. This develops the image. Of course then the piece has to be cooled and annealed so it doesn't break.



One cool thing is that the process is reversible. I don't think I'm going to do that with this piece. Better exposure control could be done with UV lights, but sun works, it just isn't as predictable.



This is a process that needs a lot of practice - both in the blowing and in the image exposure/development process.