Video transcript of Episode 2: Waterproof Hanky
On-screen text reads: "Do Try This at Home from the Institute of Physics. Episode 2: Waterproof Hanky."
Camera cuts to Imogen who is in a bathroom and is standing behind her willing volunteer, Sam, who is sat on a chair. She has just flipped a large glass of water over his head. She has used a cleaning cloth over the top of the glass to prevent the water from escaping, but the at-tempt fails, and his clothes are now wet.
We hear Imogen exclaim: "A total success!". She laughs as she puts the glass down. Sam starts smiling, and then also starts laughing quietly.
Camera cuts to Imogen who is sitting behind a table. She is alone this time and ready to start presenting.
Imogen: "Hello welcome to Do Try This at Home brought to you by the Institute of Physics. We’re making these videos because we want parents and carers all the way around the UK and Ireland to be able to get their kids really excited and curious about the world around them – even if you can’t leave the house.
"My name is Imogen, and you might be thinking: “Imogen what are you doing in your bathroom?" Imogen laughs.
On-screen text reads: "Imogen Small, IOP Public Engagement Officer". The text then fades as Imogen continues to present.
Imogen: "The reason is this is not my bathroom. I’m staying with my in-laws at the moment and this trick has got the potential to go a bit wrong so I’m presenting from somewhere nice and waterproof. This trick is called the waterproof hanky and I love it!"
Camera switches to a close-up shot of the table. Imogen picks up a large, clear drinking glass and places it upright on the table.
Imogen: "The first thing you’re going to need is a glass. The next thing you’re going to need is a hanky. Now I don’t actually have a hanky so I’m using one of these cleaning cloths. Don’t use a paper hanky or kitchen roll – it will not work. I speak from experience."
Imogen has picked up a cleaning cloth and unfolds it before the camera.
The next thing you’re going to need is a plate and finally you’re going to need a source of water.
Imogen picks up a large, flat tea plate and shows it to the camera, followed by clear jug that has been filled with water. We hear both being placed down on the table.
Imogen: "The first step is to prove to your family that your hanky is not waterproof at all. So, what you want to do is just drape your hanky nice and loosely over the top of your glass and then pour water through it. You’re aiming to get your glass half full."
Imogen moves the glass to the centre of the table, picks up the cleaning cloth and places it, unfolded, over the top of the glass. She pushes gently in the centre of the cloth, so it dips a little. She then grips the cloth around the outside just below the rim and picks up the jug. She positions the jug above the centre of the glass and the cloth and pours in some water. When she removes the jug and lifts the cloth, we can see the water is in the glass. She places the jug down.
Imogen: "The next step is to show to your family that the hanky can be made water-proof. So, what you need to do is now stretch it over the mouth of your glass."
Imogen picks up the cloth again and stretches it over the top of the glass.
Imogen: "If you’re doing this trick with your family you might want to get slightly smaller glasses so they can get a really good kind of grip on the material around the outside. Then put your plate on top and you’re going to aim to flip your glass hanky/plate combination in one really quick motion so that it’s completely upside-down. You should be able to take it away and the water does not leak out."
Imogen grips the cloth firmly around the outside with one hand whilst placing the tea plate on top with the other. She then flips the glass and plate upside down so that the bottom of the glass is at the top, and the plate is at the bottom. She then carefully removes the plate. We then see the water has stayed in the glass, and she waves her hand underneath the glass to show that the water has stayed where it is and is not leaking out.
Imogen: "Once you’ve practiced this a few times bring in the help of a volunteer. Sam! Can I borrow you for a second?"
The camera cuts to Sam sitting on a chair and Imogen standing behind him with her glass. Sam looks around at Imogen.
Sam: "What are we doing?"
Imogen smiles and Sam turns back to the camera.
Imogen: "Take your glass and your plate put it over the top and, remembering to keep that cloth pulled nice and tight, flip the whole thing over your totally willing volunteer’s head and then take away the plate."
Imogen repeats the experiment by gripping the cloth around the top of the glass, placing the plate on top, and then flips it upside down over Sam’s head. Sam pulls a face, expecting the worst. The water stays in the glass this time, and Sam looks up at the glass, slightly surprised that he’s still dry.
Imogen: "Ta dah!"
Camera cuts to Imogen sitting behind the table on her own again. She has an empty glass, a jug of water and her cloth in front of her.
Imogen: "What’s going on here and how can you explain it to your family? If you look at your hanky really closely there are loads of teeny tiny holes in the cloth. This lets the water travel through it and air go through it as well."
Imogen brings the cloth close to the camera and shows the holes in it. She then puts it in front of her mouth. We hear her blow through the cloth.
Imogen: "Now get your hanky nice and wet. Can you blow through it? It’s actually much, much harder and that is because we have water blocking up all of those tiny, tiny holes, so for the air to go through it’s got to push the water out of the way and that’s actually pretty difficult."
This time, Imogen takes the cloth, scrunches it up into a ball, and places it in the jug to get it wet. She takes the cloth out of the jug and tries to blow through it again. It sounds like it’s much harder this time. She then opens out the cloth to the camera to show the holes in the cloth again.
Imogen: "How can water block the holes I hear you cry! Have a look at this picture."
Camera switches to a picture of pond skater standing on the surface of some water.
Imogen: "The surface of the water looks like it’s covered in a stretchy skin almost like the surface of a balloon."
Camera cuts back to Imogen again.
Imogen: "This effect is called surface tension and that surface tension is strong enough to be able to hold up my pond skater so that it doesn’t sink. It’s also a really cool thing that you could try out with your family with this paper clip. With a glass of water that’s completely full the surface tension over the top is strong enough to be able to hold up something that should sink like a paperclip. And as soon as we break that surface tension my paperclip sinks to the bottom."
As Imogen speaks, the camera cuts to a close-up shot of a glass full of water. A paper clip can be seen floating on the water. When Imogen taps the surface of the water, the paperclip sinks to the bottom of the glass.
Imogen: "Surface tension is a bit like a balloon stretched over a hole. Camera switches to a close-up shot of two glass, one large and one small. Each glass has a balloon stretched over the top of it."
Whilst Imogen is speaking, the camera cuts to a close-up shot of two glass, one large and one small. Each glass has a balloon stretched over the top. The narrow neck of each balloon has been chopped off so that it can be fitted over the top of each glass. She uses her first finger to press down on the balloon. The balloon stretched over the larger glass can be pressed down more easily.
The camera cuts back to close-up shot of a full glass of water and the jug next to it.
Imogen: "Now with a glass of water without a hanky when I flip it over the surface tension is nowhere near strong enough. It breaks easily across the large mouth of the glass and the water pours out."
Imogen pours some of the water into the jug to demonstrate her point.
Imogen: "When I add the hanky water soaks into the hanky and blocks the holes in my cloth because the holes are smaller the surface tension skin across each hole is stronger and actu-ally it’s strong enough be able to keep the water inside of my glass. Which is why my hanky becomes waterproof, your family stays dry, and you stay friends with your family."
Imogen places the wet cloth over the glass and grips it firmly. She places the plate over the top and flips it upside down again. She removes the plate and places the upside-down glass over the jug. The water stays in the glass. The camera then switches back to a medium shot of Imogen presenting to the camera.
Imogen: "If you’re not totally sure about science don’t worry. Investigate with your family, maybe look it up with your family if you need to and have fun along the way."
Have a lovely day and see you next time!
Camera switches back to Imogen and Sam after some water had dripped over him.
We hear Sam say: “It dripped all over my head!”
Imogen can be heard laughing in the background.
On-screen text reads: "Do Try This at Home from the Institute of Physics. For instructions and more Do Try This at Home films visit iop.org/athome. These experiments have not been specifically safety tested for home use, but we believe them to be safe if the instructions are followed. Adult supervision is recommended as appropriate. All experiments are carried out at your own risk."