[GlentoranMark (OP)]

Hello all, the wife got me decorating  [:-'(] but we bought this paint that goes on pink but ends up white.

Great to see all the spots we missed but how does it work?

[imatfaal]

Is that deliberate / advertised feature?  Sounds really useful for getting a decent coat of paint on the same colour surface.

[Evie]

I found an article online that talks about the very paint you must have used. Yes, it is intentionally made so that you can re-paint your white walls or ceiling and see where you've been and where you've missed.

In the article, the author contacted the manufacturer. They revealed that the pink is a temporary dye, but wouldn't explain further (don't want to let their secret out!).

Anyone have any good guesses on the mechanism that allows the pink dye to be "temporary?"

[imatfaal]

I suppose you could have a dye that reacts with oxygen/water/co2 in the air to denature and lose its colour

[Geezer]

http://www.freepatentsonline.com/EP1400574.html

Quote: "Phenolphthalein solution at pH 9.5 is a red colour but if the solution is dried only white crystals remain"

I'm surprised Bored Chemist didn't come up with this one. He could have made a bundle!  []

[chris]

What a fantastic invention; I would never have thought of doing something like this phenolphthalein trick; ingenious.

Chris

[Geezer]

The patent describes a lot of different ways that might produce a similar result. But do not be too discouraged if your reaction is, "Doh! Why didn't I think of that?"

Based on my rather limited experience, the best inventions are those that provide a solution to a particular problem. So, the first step is to identify a problem.