Secret Message Revealed After Wet
Does anybody know of a way to have a paper with a secret message on it (pretend the message says, "It Rained"), and once the paper has been soaked with liquid (water, or maybe a mild acid or base), the secret message is revealed permanently?
So like, if you had a little paper sign out in your yard with the secret message, and it rained, and the paper got wet, when you come home, you would see the dried out paper but with the message revealed.
(note, i don't actually care about a "it rained" indicator, just an example)
So like, if you had a little paper sign out in your yard with the secret message, and it rained, and the paper got wet, when you come home, you would see the dried out paper but with the message revealed.
(note, i don't actually care about a "it rained" indicator, just an example)
Lomography Konstructor - World's First 35mm DIY SLR
Office Warfare Book on Sale Now
List of Upcoming Contests (updated 6/6)
Spanish translations of Instructables / Instructables traducidos al Espanol
JULY 2013 Build Night with SUGRU
High-current, electronic sword-fighting, fancy drink pouring, and more @ Makers Local 256 Build Night!
New Instructables Books for 2013
Souped Up: Projects to Make Everything Better [Book]
Backyard Rockets Book on Sale Now
Visit Our Store »
Go Pro Today »
Maybe i can write a permanent message on the paper, then apply the Goache all over, and then (hopefully) the Goache will be easily rinsed off.
I'll report my findings!
This is an interesting conundrum! Your suggestions are awesome!
Ill post pictures later
Water sensitive paper:
http://www.qinstruments.com/uploads/media/wsp_datasheet.pdf
And here is a link to those color wonder papers people were talking about:
http://www.crayola.com/products/list.cfm?categories=COLOR%20WONDER
The issue with having water as the indicator has to do with the way invisible and disappearing inks which depend on chemical reaction (as opposed to heat or light activation) work. In most cases, it seems, this type of invisible ink is made visible (and sometimes, invisible again) through acid-base reactions. Water, being neither an acid nor a base, doesn't lend itself very well to that. I'm not saying that a way doesn't exist, because I've only cursorily examined the question, but it isn't a very popular or well known solution (ha!), if it's out there.
http://www.freepatentsonline.com/4212393.html might be useful; it describes the kind of children's toy I'm talking about.
At what temperature does copper sulphate dehydrate to "white"...?
L
I wondered whether a bit of PVA might seal it enough..?
L
, but im not sure how much pressure is needed to actually wash the ink off (like would a light rain that soaks the paper, still wash off the paint appropriately).
The paper will be ideally about business card sized, biodegradeable, and coated with a pigment that you can keep in your pocket without getting the pigment all over.
any ideas for an easily wash-off able substance?