Twistmas Advent Calendar (Part 2)
Created by Dr Matt Pritchard
At the end of 2025, Dr Matt Pritchard created an advent calendar for us consisting of 24 videos featuring optical illusions, curious objects and magical effects. On this page (and in Part 1) we’ll give further details on what is happening in each video and some additional ideas for you to explore. We suggest you watch this video before you read about each day individually below.
Day 14 – No Snow
On day 13 Dr Matt Pritchard shared an optical trick where a snowman disappears when viewed in water. It was made by laminating different layers and leaving an air gap between layers of the image.
To make a much quicker version you can use two clear plastic cups. Anything written on the inner cup will be ‘invisible’ underwater when viewed from a high angle. In the video example, the letters NO disappear.
Day 15 – Context Matters
Context matters. The same symbol can be read either as an A or H, depending on what other letters surround it.
Day 16 – Retinal Afterimage
This illusion illustrates retinal afterimage after being fatigued. Stare at the cross in the centre of the image for 30 seconds. Try not to blink, move your head or change screen position. It helps to turn the screen brightness up. After the time is up, a white image with black outlines show. For a brief period of time after this, you should experience a faint coloured glow that is correct for the scene. They’re the opposite colours to what you’ve just been looking at. Pink becomes green. Blue becomes yellow etc. Did it work for you? At Twist Museum there is an example of a famous British singer who transforms their colour.
Day 17 – Rudolf Jigsaw
This is one of Dr Matt Pritchard’s favourite arrangements for a “geometric vanish.” When four identical pieces are rearranged, they create a mysterious hole in the centre of the board. But how does it work?
Perhaps the most well-known example of these vanishes is the video with the chocolate bar that when rearranged seems to produce more and more pieces. To see how they work, look at the edges of the puzzle, you’ll see that overall, the puzzle changes size. It might only be a tiny millimetre larger on each side, but added up that’s a significant increase in area.
Day 18 – Light/Dark
An ambigram like object that when the lines are reflected in a mirror they either show up as the word Dark or Light. This was made from a font called “Lake Reflection” which has the property of each letter being a reflection as if viewed on the surface of a lake. With a mirror you only need to use half a printout to complete the word. By joining two different words together like Dark and Light, you can create the effect in the video where one side makes one word, and viewing from the other side makes the second. I’m fascinated by these ambigram like effects and you can view a load of other examples here.
Day 19 – Five Golden Rings
By placing three mirrors to create the corner of a cube you can make an arrangement that completes the quarter rings. This video was inspired by the 12 days of Christmas song. Twist Museum has a whole section of mirror based illusions and sculptures that you can interact with.
Day 20 – Mirror Magic
What’s happening with these reflections? In today’s digital world it’s too easy to say it’s sneaky editing or AI. However, this illusion is very analogue and uses a simple technique that has been used on stages to make ghostly appearances and vanishes. The left half of the frame contains a mirror and the right have is just transparent glass. An object behind the frame is invisible on the lefthand side and is replaced by a reflection. On the right hand side it is visible and you can have two different objects with a phantom reflection.
Due to various circumstances, the lighting here isn’t as good as it could be and the rigging impeded the choreography in certain places. On much larger scales, this can be better compensated for BUT the tradeoff is using incredibly large (and heavy) mirrored glass.
Day 21 – Noe(l)
There’s something wrong with this! There is no letter L in the foreground. No L. Noel.
To make this Dr Matt Pritchard simply stuck on a piece of black paper to the surface of the mirror.
Day 22 – Prof Pepper’s Snowflake
A short walk from Twist Museum is the theatre where Prof Pepper first demonstrated his optical magic by making a ghost appear on stage. Reflecting a bright object off a glass screen allowed the audience to see both a reflection and a scene behind the glass. Augmented reality.
This simple craft uses a mobile phone to be the source of the bright ghostly image and a thin piece of clear plastic inside a bell jar. Angled at 45 degrees it bounces the reflection back at the viewer. In a previous blog for Twist Museum, Dr Matt Pritchard gave more of the history to this famous illusion and another simple craft to make a Ghost Scope.
Day 23 – Rudolf’s Nose Flicker
Another simple craft that has a magical effect. Flick the side of the card and the two flaps behind switch places.
Day 24 – Naughty or Nice?
Naughty or Nice? A lenticular like construction changes the word based on what angle you view the grid at. There’s an array of horizontal bars a few millimetres above a printed sheet which has the two words interlaced. When viewed from one angle, you can see one half of the interlaced words and the other half is hidden. The mirror’s reflection shows the opposite scenario.
Give the illusions a go for yourself and share your creations with us on social media. Part 1 can be found here.
