´óÏó´«Ã½

Ever wanted to stretch your hair? Dr Chris and Dr Xand create a step-by-step humidity measuring machine (otherwise known as a hygrometer) to stretch and shrink your hair!

Step 1: Cut part of the front or back off a cereal box. Get a grown-up to help you. Cut two-thirds of the way down, leaving the back and sides intact.

Step 2: Take some of the excess cardboard you've just cut away and cut out a 7cm by 3cm triangle.

Step 3: Tape the penny to the pointy end of the triangle.

Step 4: Stick one end of the hair to some tape and fix it to the triangle.

Get a grown-up to help you with the sharp pins in these next steps.

Step 5: Put a pin through the fat end of the cardboard triangle using wall tack.

Step 6: Attach the pin to the cardboard box using the same method with the wall tack.

Step 7: Take a second pin, wrap the other end of the hair around the head of the pin and tape it down.

Step 8: Using more wall tack, push the second pin through the top of the cardboard box and tape down, making sure the hair strand doesn't break but is straight and taut. This is very fiddly, so ask your grown-up for help.

Step 9: Calibrate the hygrometer by using your hairdryer to blow hot air on the hair. This removes all water molecules from the hair.

Step 10: Write 0% humidity on the box next to the point of the triangle.

Step 11: Next, put the hygrometer in a very humid environment (like a shower room) and watch the triangle begin to point down as the hair strand stretches.

Step 12: Write 100% humidity on the box next to the point of the triangle. 

Step 13: You now have a fully functioning hygrometer, allowing you to find the humidity of any room in your house. Explore which areas have the highest and lowest humidity!

Watch the whole episode of Operation Ouch! Do Try This At Home: Stretchy Shrinky Hair on ´óÏó´«Ã½ iPlayer.