I'm hoping someone remembers how to do this because I looked and couldn't find anything.
I can remember as a kid taking sheets of black construction paper and putting objects on them and letting them sit in the sun for a while and coming back to find faded paper with images on it.
Can this still be done with modern construction paper? About how long does it take? Has anyone ever tried this in a large or medium format camera, and if so did it have a wow factor for kids?
I want to show this no processing photography trick to a three year old.
Ilford used to make a POP kit for schools for making Photograms. There was an old process where a fully exposed "black" print was soaked in Potassium Iodide & dried then when re-exposed to sunlight the image would bleach where affected by light, but I have no details at hand.
They sell cheap pre-sensitized cyanotype kits for this... "Sunprint" or some such name. In science stores...I think Freestyle sells them too. Just expose, then put in water IIRC.
Thanks, I am going to try the cyanotype paper, it takes about an hour and that should be about the right amount of time for a three year old in a here do this, ok go play, ok now do this, look you made a photo kind of way.
There is a lot of variability in the light-fastness of dyes. You might consider getting an assortment pack at the dime store, and doing a simple test. As I recall, blues and greens tend to be the most stable (in cheap consumer goods) while reds and yellows are pretty fragile. There actually is no "black" dye (one that absorbs all colors equally) and the black paper may well have a pigment (carbon black is cheap) along with a mixture of complementary dyes.
If you can befriend a darkroom guy with some expired/fogged/unwanted photographic paper, you will really be set to go!
Putting typical RC photographic paper in the sun (especially the kind with built in developer) will cause an image to form. They used this process in those 6 month long pinholes, no development, just scan.
sun prints with regular photo paper is easy and fun it doesn't take long ..
photogramming with regular rc paper is fast and easy
and if you want to do something fun
stick a piece of rc paper in a camera, leave it on B while you are making your photograms,
for a half hour pointed towards something in the sun
and you will get a negative printed on the paper ...