disappearing writing effect

[EmilyB]

HI

the director wants to use an effect he saw in an other play. The actors had what looked like water they wrote on a screen and it showed up as dark lettering complete with wet dribbles etc which then slowly faded away. he is convinced it wasn't projected but was done live. I thought maybe some sort of UV activated invisible ink? any other ideas how we could do this?

Thank you

[david.elsbury]

I'd use UV reactive paint, and then fade up normal lighting to wash it out. Most UV sources are discharge lamps so you can't directly dim them, you can of course use a mechanical douser or shutter. You can also get UV LED lights now.

 

Otherwise what about painting in, say, red, lighting it in white (to see the lettering) and then fading out the white and fading in a red light? The red would disappear.

 

Depends what effect the director wants, and how much $$$ they are prepared to throw at the effect!

 

David

[EmilyB]

Thank you

I was thinking the UV route but he wants to be able to wright different things in the same space i.e. the writing fades then something else is written on the screen a couple of times. but with the UV I can't think if away of doing the different sentences without the previous ones reappearing.

[rossmck]

There's a few disappearing inks out there ... seen it used in joke waterpistols etc, maybe something like that ?

 

Or maybe it *was* water and the surface itself was special - something similar to the kids toy "aquadoodle" which is essentially a blue fabric covered by some sort of white material which becomes translucent when wet and dries becoming opaque again.

[alexadamson]

My nephew has one of these - Link

 

You fill the "pen" with water, it writes on the mat and as it dries it disappears.

 

Might be worth spending a £10 to see what the surface of the mat is and how it works etc..

[ImagineerTom]

Very simply, this isn't going to be as simple as it appears to be (like all effects - the skill is in making weeks of planning and thousands of pounds worth of equipment look like an old piece of paper) - the Aqua-doodle sort-of-does what you want but it takes hours for the ink to "vanish" - it can be sped up using artificial heat but then there's the complications of controlling the heat safely to ensure it fades EXACTLY when you want and doesn't over-heat the surface / actors / set AND complies with all relevant safety codes. I'd bet good money that what your director saw wasn't as "clean" as they remember it (directors, more than anyone else are guilty of "believing the magic") and that it probably was projected or screen based.

 

I can think of a couple of light-based solutions but we're still talking complicated application of unusual technologies - the sort of stuff that's going to take more than a sentence to describe and lots of playing/prototyping to get something as clean as you're imagining it to be.

 

t

[Andrew Edwards]

My son has a Thomas the Tank Engine 'aqua doodle'. It has far less designs on it than the one shown in a previous thread. The clear white area is about 1m square and the ink effect is green. You might be able to pick one up on fleabay.

 

As for drying time, it's minutes not hours. The Thomas one comes with a tool for drawing a train track which is followed by a Thomas train. After about 3 or 4 laps it is dried enough for the sensor in the train to lose its place and gone in under 10 minutes. Under stage lighting conditions, I reckon it would be completely back to normal after 3 or 4 minutes, 5 at the most.

 

It might be possible to make your own with the right combination of fabrics. The top layer just needs to be opaque enough when dry and go translucent when wet and stick to the coloured (probably plastic) sheet underneath.

 

My first choice would be an interactive whiteboard however.

 

Edit: Spelling

[EmilyB]

Thank you for the suggestions

I think I will try some of the joke disappearing ink before trying to make a 4m wide aquadoodle.

thanks

[sleah]

My first choice would be an interactive whiteboard however.

 

Or an adaptation of Friispray which uses rear projection.

 

Think of the ability of an interactive whiteboard, but rear projected using an infra-red 'pen'. However, you would need customised software to achieve the desired effect.

[p.k.roberts]

I don't know if it would work in your application, but I have been convincingly 'gotcha'd' by this stuff in the past ..

 

http://www.toyday.co.uk/shop/jokes-magic/practical-jokes/a-bottle-of-disappearing-ink-liquid/prod_3687.html

[bigclive]

And once you've used up all the disappearing ink in the bottles you can fill them with REAL ink and give them to unsuspecting friends.

 

It does sound like the original effect used standard disappearing ink. It seems to react with air for the effect. You can find instructions for making it online, but if you only needed a small amount then bottles from the joke shop would do. I'd suggest keeping it in the bottles until just before use.

[ojc123]

Old habits die hard. The Chemistry teacher in me wanted to know what disappearing ink was. A well known search engine gave me this.

 

If you do go about making it then remember two things. Sodium Hydroxide is particularly nasty if it gets into your eyes at even 0.5M. They're talking about messing with 6M and 3M solutions to make your ink. I'd be very careful with a risk assessment before I'd prepare that kind of solution of Sodium Hydroxide. That could cause real damage to skin and eyes and pretty well anything it comes into contact with. Though it's very dilute in the finished solution so shouldn't be a problem.

 

Phenolphthalein is quite a powerful laxative and you would want to be careful with it. Both thymolphthalein and Phenolphthalein are irritant and need care in handling. Again the finished solution is quite dilute and shouldn't be a big problem.

 

Take care in the preparation of this if you follow their instructions.

 

Intriguing. Not something I've tried but I feel an experiment coming on.

 

E2A it does react with carbon dioxide in the air. The carbon dioxide neutralises the sodium hydroxide and the indicator changes colour.

[EmilyB]

The disappearing ink seems to work quite well and is defiantly simpler than the UV things I was originally thinking

Thank you