I was uploading as gimp tutorial but then i realized that would be totally misplaced
Gimp is not much used, only to apply a silhouette brush or open a silhouette image

Still i like much this process and the results so i upload in Chit Chat

INTRO (This is not needed to execute the tut,you may skip all this part in greenish Italic! )This was part of a workshop i created to teach photography to per-scholar children (from 3 to 5 years ), i hate here the word "teach" that may be so misleading

In the format i was a Wizard , the Wizard of the Black and the White, a bizarre magician VERY JEALOUS of his secret, and the only most courageous would get a chance to be initiated, so no i never tried to "teach" on the contrary my apparent intent was kept the secret but then since as Wizard i was not only bizzare but also distract , i was forgetting everywhere clues

So always all the children were able to survive the initiation rituals and end the course , and so built and use a real photographic machine (simple as a box with a hole , hole that replaced the lens) and a Darkroom, and in the darkroom develop and fix negatives and even create objects from their photo )

Obviously the first concern was security and the "initiation rituals" were mostly to impose security but in the most funny and choreographic way
As example to be initiated was needed pass the " 4, Basins " test :
the wannabee initiated must undress , and all the class help to prepare his special white robe, pratically the child is wrapped in a cloth of Scottex fixed with tape, and once dressed the challenge start , the Basins are in front, one filled with innocuous blue liquid, the middle basin is filled with pure water, Yellow ink and again water

Initiated should be able to immerse a sheet of paper in the first basin, rinse it well in the second, immerse in the 3rd basin, and rinse again in the last ...it sound simple? no it is not so simple :

First has to be done in a almost complete darkness ,room has to be carefully obscured only 2 candles are permitted

Initiated should never, never touch the sheet of paper or the liquids in the basins with bare hands, may only use modified clothespin... also should take care to rinse very well the paper sheet , the Yellow liquid has never to be dirtied with trace of Blue,

But the most challenging is the apprentice White Scottex Robe that completely wrap the child from tip to toe

...at the end of the Basins proof the White Scottex Robe is carefully observed by all class for the faintest traces of yellow or blue d, and if any drop or stain found test has to be redone

After that is not need to teach anything else,
only to replace colored liquids the developer and the fixer, the sheet of paper with real photographic paper and all children can start to print their negatives.

Oh i almost forgot, the candle light, few known that candle light is almost equivalent of the red or yellow darkroom light.
And since the peculiar characteristic of the photographic materials and processes i used, it was a perfect equivalent

Well this the origin , i just adapted this part for more mature readers


Paint with light on living leaves

To accompany the gift of a plant Instead then the usual ticket you may embed a message or a image in one of the leaves

No harm would be done to plant, except that sort of tattoo, a tattoo that will laste a couple of weeks before naturally fade away.

1)
First requisite a plant with large leaves , large and with a flat surface, or a surface that may be temporary flattened without damaging it )

2)
Then chose or create a adapt image black on transparency, without intermediate grays
You may found ready a lot of "silhouettes" (i.e on openclipart , or even as gimp brushes) ,
if you want add a text (again only the silhouette count )
If needed scale , the leaf has to be a bit larger of this image
Avoid image with too tiny lines and details

3)
Print your image , should be black on transparency , any material supporting transparency is fine

4)
Now carefully fix the image to the leaf, it should adhere the most possible to the surface but obviously you can't just glue it:
i often make a sort of transparent sack and then i put in on the leaf.
But are many other ways ...best method depend from size and shape of the leaf

5) wait a few days
the black in the image image will block sun rays, blocking so so chlorophyll syntheses , chlorophyll gives the green
...without the color shift to brown or reddish

Once you removed the image the design on the leaf will remain quite long visible

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A variant
there is a more know but for me less fascinating variant, less fascinating because done on dead leaves

Anyway ,pick up or found a large leave STILL VERY GREEN , repeat 4 and 5 , and expose the leaf to the light

The result would be similar but with inverted tonality, in this case the black of the image will delay the decay of chlorophyll , while the rest will turn quickly in red or brown