Angus was a 6th Form student at St Leonard’s School in St Andrews. He created this project as part of his studio work for the IB Visual Arts course.
The Pepper’s Ghost technique has been used by magicians and illusionists since Victorian times. More recently, music festivals have used it to create interesting visual effects. That’s how Angus first became aware of it.
Creating the right artwork
Angus wanted to create each part of the illusion by laser cutting three panels of black acrylic. He wanted the first sheet cut with face details, the second sheet cut with stars and the third with cloud details. He chose 3mm acrylic as it was robust enough for the job. It was important that light wouldn’t pass through the body of the material to spoil the effect of light travelling through the holes in it.
In order to laser cut the black acrylic, I needed vector files. Shapes for each star and each cloud outline must be surrounded by a single hairline vector line that the laser can follow. Angus and the school Art Department had no previous experience of laser cutting, and none of their artwork packages were able to generate vector artwork, so there was a learning curve to climb until I had the files I needed. Sometimes artwork creation can be the trickiest stage of a project.
Creating the illusion using acrylic
To create the Pepper’s Ghost illusion, Angus laid each of the laser cut black panels flat on a light box. You can just make out all three sitting one behind the other in the picture. The clouds are at the front, the stars behind that and the face is at the back.
Light shone from the light box through the laser cut holes in the black acrylic. This light was reflected in the clear acrylic sheets set above the black panels at 45 degrees, facing the viewer. You can see the front clear acrylic panel easily.
The transparent image appearing at 90 degrees to the black acrylic sheets. It incorporates the reflections from the layers of light reflected by the clear acrylic. All three reflected images superimpose to create the illusion of Angus’ face floating in the night sky. It’s an impressive effect and Angus’ ambitious installation was a huge success.
Each year, the Art Department has a show of pupil’s artwork for different year groups.
FifeX asked us to help with an educational project for SEPA (Scottish Environment Protection Agency). They wanted some bespoke models to help to educate schools and other groups about flooding and its effects including broken trees, damage to property including buildings and vehicles, and infrastructure like roads. These models would have to be robust and stand up to handling by groups of all ages.
Fifex knew that Perspex would be perfect for the job. It can be sourced in a wide range of colours and can be cut into intricate shapes. They decided on 5mm thick Perspex to make the shapes sturdy, and they designed the pieces so that the car, house and tree shapes could slot into bases. 3D models would have more impact and make them easier to handle.
A good fit
The main challenge was to make sure that the tabs and slots on the shapes and the model bases fit together well. If they were too loose, the models wouldn’t be robust enough when glued together. If too tight, they wouldn’t fit together at all! When materials are laser cut, the width of the cut is determined by the nature and thickness of the material. It’s always worth checking the artwork by making prototypes so that dimensions can be adjusted if necessary. Also, material thicknesses can be nominal and have margins for error, so it’s always worth checking. In this case, we got it right first time and the fit was perfect.
Ken Boyd, Director of FifeX, said, ‘Laser cutting the shapes was a fantastic solution for us as the models were to look accessible for a young audience with fun, interesting and recognisable shapes. Brightly coloured Perspex was the perfect material. LaserFlair helped us with initial prototyping and a very quick turn-around on the final product as well as some spares and extra bits.’
LaserFlair makes fun and funky acrylic jewellery for Jaggedy Thistle in Dunkeld. We laser cut their reindeer brooches in the run up to Christmas along with highland cows and Scottie dogs. This is how it all happens.
We need vector artwork to create items like this. Jaggedy Thistle provide the artwork for their bespoke products, and the acrylic in the colours they require.
Vector cutting detailed shapes
Vector artwork is very simple. It consists of hairline shape outlines, and the laser follows the lines in the artwork to cut out each shape. There is a vector line for each outline cut on a piece. In the case of the reindeer in the picture, we cut the eye shape first. When the body is cut, the whole reindeer can drop out of the acrylic sheet and is then in the wrong position to cut out internal detail. This is why we set the machine’s cutting order so that internal details are cut before outline shapes. We minimise waste by using our laser cutting software to tile shapes which maximises yield from the acrylic available.
Protecting the pieces
Acrylic has a protective film on each side to prevent the surfaces from scratching. We leave it on during production to protect the acrylic surface from the heat of the laser which causes discolouration near the cut edges. After manufacture, it protects the pieces during shipping, keeping each shape in perfect condition as acrylic is easily scratched.
When Jaggedy Thistle receive their delivery, they remove the protective film from each brooch. Then they add the red noses and brooch pins, and mount them on cards for sale. Aren’t they cute!
Perspex branded acrylic is the best quality. Other brands have additives that make the cutting process significantly slower and smellier on the laser. This adds to production time costs and can decrease operator comfort.
We had to complain about some 8mm white acrylic that was not Perspex branded. We had bought it for a project with a designer who was prototyping a product. When we cut it with the laser, the edges went brown when they should have stayed white, and it was all down to the makeup of the acrylic. We also had to run the machine at a slower speed than we’d expected for the thickness of the material which made the process less profitable for us. Thankfully, the supplier gave us a refund for the material as they agreed that it was of inferior quality to branded Perspex.
We learned something that day, and now we never order acrylic that isn’t Perspex because of these problems.
How is acrylic made?
Acrylic, unlike plywood, is less varied in sheet thickness, but there’s more to it than that. There are two kinds of acrylic, cast and extruded, named after their production processes. Cast acrylic is made by pouring the acrylic into a mould to set. Extruded acrylic is rolled to a set thickness during the production process.
So theoretically, extruded acrylic should be closer to the nominal thickness of the sheet. You won’t see the same thickness differences between cast and extruded acrylic that you’d expect between nominal and actual thicknesses of plywood, where you can expect differences of 0.2 to 0.3mm. The errors are far smaller.
But not all acrylics are equal, and this is the important thing to watch out for. It could affect the look, quality and cost of your product.