|MadSci Network: Chemistry|
Hello, Angela – it is difficult to give you a full answer to your question without more information, but I will try nevertheless. You do not say whether this is colour as opposed to black/white, or whether your original is a print or a negative. Chromatography paper has the property of easily absorbing solutions while calendared papers have glossy surfaces which make it difficult for solutions to absorb, I would guess ease of solution absorption is the reason for suggesting chromatography paper. My best guess at what is suggested here is that you are making a print from a negative, by contact printing – i.e. shining light through the negative onto the print paper and then fixing the image. By contact printing, I mean that the negative lies directly on top of the paper, and so the copy of the image, the print exactly matches the size of the negative. To do something like this you need to sensitize the paper to light, and the solution which does that most easily is silver nitrate. If you have access to silver nitrate, you need to be careful. Make sure your teacher is on hand to help. It is toxic, as well as light sensitive, and you do not want to get any on clothes or skin. Silver nitrate dissolves in water to give a colourless solution but it is unstable to light and will go black as silver precipitates on the action of light – so will skin and clothes! I would guess that what you could do is soak the paper in a dilute solution of silver nitrate – in dim light. Store any solution in an opaque bottle clearly labelled – and when you have soaked the paper hang it up to dry in a dark place. When it is dry, place a negative over it and place the paper in the light – preferably strong sunlight in such a way that the negative is held flat to the paper and is unable to move. A contact printing frame is usual, but a spare or old photograph frame will do. Watch the paper darken where the negative is light. As soon as the paper has darkened in the areas where the negative is lightest ( to a level about as dark as the darkest area of the negative, remove the setup from the light and now we have to remove the paper from the frame and fix the image. This is done with hypo – a solution of thiosulphate – ammonium or even sodium will do. Put the solution in a tray big enough for the print, immerse the print, and leave it for a good while. Finally remove the print, wash it in running water for a while and hang up to dry. By the way, if the original was a print, you might be able to do the same thing and get a negative copy, but you would have to leave it in strong light for a long time. Only experimentation will tell you how long. If you can do that, you can then reverse the process to get back a positive image. Phew! Good luck, and if my attempt answer your question has missed the mark, let me know either by direct e-mail, (email@example.com) or by asking another MadSci question – with more background information.
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