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Arts & Humanities Research (MPhil) (PhD)

Helen Slater Stokes

Research Project Title: Exploring the optical perception of image within glass.

Supervisor(s): Martin Smith, Dr Heike Brachlow

After graduating from The Royal College of Art in 1996, with a Master's Degree in glass design, Helen set up her business Helen Slater Glass, in Oxfordshire. Since then she has exhibited both nationally and internationally and has worked on public and private commissioned works.

Helen also lecturers on a part-time basis at De Montfort University, Leicester. On their Design Crafts degree course.

Within her PhD research she has pushed the boundaries of image perception in glass. For this research she worked in collaboration with lenticular lens producers, printers and the casting industry, in order to create works that allow the image to recede into and supersede the outer boundaries of the glass body.

PhD Research: Exploring the Optical Perception of Image Within Glass

Within the contemporary world, 3D film and television imagery is at the cutting edge of visual technology, but for centuries we have been captivated by the creation of visual illusions/allusions that play with our perception of the world, from the auto-stereoscopic barrier methods pioneered in the late 17th century by the French painter G. A. Bois-Clair to the ‘Op’ art movement of the 1960s and, more recently, Patrick Hughes’ ‘reverse perspective’ paintings.

By building on these new and old technologies I have extended my own practice, which engages with the 2D image as a 3D allusion/illusion in glass, by examining how this type of image can be created and perceived within glass. I have explored theories of optical perception in connection with the binocular recognition of depth and space, as well as kinetic clues to distance through motion parallax monitoring and assumptions about default linear perspective, light and inference within our personal schemata.

- ‘Optical illusion’ is used to mean an instance of a wrong or misinterpreted perception of a sensory experience; the distortion of senses revealing how the brain organises and interprets visual information; an individual’s ability to perceive depth, 3D form and motion.

- ‘Allusion’ is used to imply a symbolic or covert reference.

My practical research focuses on the perceived creation of the 3D image within glass and explores the notion of glass as a facilitator in working with and challenging the themes of 3D image perception. I have particularly addressed artistic spatial illusionary methods, reverse perspective techniques, auto-stereoscopic image-based systems, parallax stereograms and lenticular print and lens technology.

Through building on my previous practice of working with multiple-layered images within cast glass, combined with more complex and scientific optical methods, I have explored the perception of the image by working with new and old 3D technologies in order to produce a body of work which examines this perception within glass.

During my research I have developed an original casting process, a vacuum-casting lost wax process for glass, in addition to producing an accurate industry standard lenticular glass lens. This research intends to provide a theoretical basis for new glass working techniques, both within the glass artist’s studio and in the commercial world of print, towards applications within architectural design, installation art and image-based artwork in general.

Glass Optical Sculptures — This short film illustrates the range of optical glass works that I make. These all relate to 'spaces', either places with an emotional resonance or the mathematical emotionless analysis of these areas.
Click on the image above to view my PhD thesis in full.

Overview of My Research

As with all research, it is crucial to explore the context you are working in.

The Image

For this I examined how the two dimensional image has historically evolved and how these developments relate to the optical cues that the eye and brain adopt, in order to form a perception of three dimensions.

As an artist who loves to draw, it was really interesting to learn optically why the rules of drawing, which I have learnt over the years, are so convincing in creating the illusion of a three dimensional space or scene.

Optical Perception

The understanding of how we perceive three-dimensional depth, via our binocular vision, is not new. As early as the 4th century BC Greek mathematician Euclid was credited by some with the discovery of the principles of binocular vision. But today, with the interest in 3D virtual technology, the launch of glasses-free 3D televisions, virtual reality headsets and now augmented reality, the process of working with binocular vision, imagery and kinetics to create the illusion of 3D depth is being explored further than ever before.

Surveying the technological developments surrounding the image and the illusion of three dimensions was a further extension of the context. From early lens-based plotting devices that facilitated the translation of the world into a graphic reference, to scientific stereoscopic apparatus and early 3D technology, this contextualised the image and our desire to capture realism through illusion. Here I was intrigued by the scientific endeavours that have led to today’s convincing parallax-based 3D virtual realisations of real and imaginary worlds.

This short film illustrates the approaches explored and some of the glass works produced over my six years of part-time research.


Kiln Formed Glass


Den — Cast glass sculpture : 29 x 19 x 5 cm. Photography by Alick Cotterill.
Field View II — Cast glass sculpture : 38 x 28 x 5 cm. Photography by Alick Cotterill.
Through the Mist — Cast glass sculpture : 24 x 19.5 x 4cm. Photography by Helen Slater Stokes.
Looking Back in Time — Cast glass sculpture : 40 x 30 x 7cm. Photography by Helen Slater Stokes.
Autumn — Cast glass sculpture : 9 x 24 x 5 cm. Photography by Helen Slater Stokes.
Memories — Cast glass sculpture : 27 x 24 x 5.5 cm. Photography by Helen Slater Stokes.

This series of pieces create a dialogue around our notions of a 'place'. The emotional resonance it might have and our human sentimental or associative attachments.

Field View: This range of work is an exaggeration of what happens optically if we were able to capture the gathered image from just one of our eyes as it instantaneously flicks across a view gathering data. This captures a sharp focus on the area of interest and then the gradual blurring as peripheral vision tails off.

Through the Mist: In this photographic technique, blur, or bokeh, is used to exaggerate depth or draw the viewer to a particular focus. As mentioned, our eyes almost instantaneously find a focus while they dart across a scene: by focusing on several areas to construct a realistic image of the space or object as a whole. In photography it is rarely possible to focus crisply on everything within a shot and it is this blurring that distinguishes photography from human vision.

Den: This work looks at tonality and its use traditionally in depicting optical depth. The internal image illustrates a tunnel of trees receding into the the distance. Darker tones fade to lighter greys, as the space recedes. Again this is a space that no longer exists, which has been drawn from memory. This place has been pictorially recreated to appear three dimensional, preserved within the glass forever.

These effects in/on the glass bring a poetic reference to the pieces, adding a further emotive or human dialogue.


Cast Glass and Glass Enamel


Oculus — Optical lenticular glass sculpture : 27 x 24 x 6 cm.
Oculus — Optical lenticular glass sculpture : 27 x 24 x 6 cm. Photography by Ester Segarra.
Acuity — Optical lenticular glass sculpture : 27 x 24 x 6 cm. The Imagine Museum, International Glass Collection, USA.
Acuity — Optical lenticular glass sculpture : 27 x 24 x 6 cm. The Imagine Museum, International Glass Collection, USA. Photography by Sylvain Deleu.

These lenticular glass sculpture appears to hold coloured spheres within, that track and follow the viewer.

Oculus, here coloured forms appear to breach the glass that holds them, animated as if rolling out of the glass. They question our perception of the 'space within', whilst also functioning as a time based image plotting not only spatial references but also the passing of time.

Acuity also addresses the space within an object. But here this work functions based on the miss alignment of the optical lens, converting smooth spheres into saw-like discs. These forms, in the glass, spin as the viewer engages with them, keeping track and time with the observer. This piece has been purchased to be part of the International glass collection at the Imagine Museum Florida, USA.

In this series dialogues around space and the time based image emerge, in addition to the necessity for interaction with the works.


Cast Glass and Digital Ceramic Transfer


Each 27 x 24 x 6 cm
Asymmetric Vortex — Wall Mounted Glass Lenticular Sculpture: 42 x 42 x 6.5 cm. Limited edition of five pieces. Photography by Alick Cotterill.
Asymmetric Vortex — This glass work is made up of a white opaque glass sheet with a fired on digital lenticular image and a cast glass lens sheet. Photography by Sylvain Deleu.

This works explores 'Space' as a mathematical computation. Creating a virtual perceived space within the work that appears to be deeper than the 6mm glass which contains it.

When viewed the spiral-like form animates following and pulsing as the observer moves around the piece.


Kiln Formed Glass, Digital Ceramic Transfer


42 x 42 x 6.5 cm
Virtual Landscape II — Cast Glass and Digital Ceramic Transfer: 29 x 24 x 5 cm.
Virtual Landscape II — Cast Glass and Digital Ceramic Transfer: 29 x 24 x 5 cm. Photography by Ester Segarra.

Virtual Landscape II: This is a unique cast glass sculpture that uses original glass processes, developed during my PhD, to create the perception of additional depth and three dimensionality, within the drawn landscape.

Drawings from memory, of a place that no longer exists, have be digitally captured and manipulated to recreate this place in three dimensions within the glass. This is a landscape that you are now able to look around, which animates as the viewer moves, and sways in the breeze.

It is a place that has been virtually fabricated to be preserved forever within the glass.


Cast Glass & Digital Ceramic Transfer


29 x 24 x 5 cm
Breaking Ground — Kiln formed glass, digital ceramic transfer and stainless steel : 47 x 38 x 6.5 cm. Lenticular glass sculpture comprised of two parts - Firstly, an opaque white sheet with the fired on digital image and printed landscape image and secondly a cast glass lenticular lens. Photography by Sylvain Deleu.
Breaking Ground — Kiln formed glass, digital ceramic transfer and stainless steel : 47 x 38 x 6.5 cm.

This wall mounted lenticular glass sculpture discusses the changes that happen overtime that change our landscape. The field in question has been built upon and the place changed forever. This was a place I knew, it had a resonance, but as the planners move in the place becomes a mathematical space, rather than one with an emotional attachment. Breaking Ground speaks of this change of purpose and change in emotional perspective.


Kiln Formed Glass, Digital Ceramic Transfer and Stainless Steel


47 x 38 x 6.5 cm
Geometric Perspective — Cast glass and digital ceramic transfer : 38 cm diameter x 11 cm deep. Photography by Ester Segarra
Tree line — Cast glass and digital ceramic transfer : 45 x 21 x 6 cm. Photography by Helen Slater Stokes

This piece explores one of the optical cues that the brain used to create a perception of the space around us and how this recognised cognitive response can be manipulated.


Cast glass and digital ceramic transfer.


Inverted Symmetric Cone — Wall mounted lenticular glass sculpture : 42 x 42 x 6.5 cm.
Inverted Symmetric Cone — Wall mounted lenticular glass sculpture : 42 x 42 x 6.5 cm. Photography by Helen Slater Stokes.

Inverted Symmetric Cone creates the illusion of a cone-like form superseding the surface of the glass and animating or pulsing, as the viewer moves around the piece.

Again this work challenges our perception of what we are seeing, whilst also analysing our notion of the space around us and the optical cues we take in order to interpret these places/spaces.

This work is comprised of two pieces of glass. The first is an opaque white sheet of 3mm glass with the digital image fired onto it and the second a cast glass lens, again only approximately 3mm thick, which facilitates the illusion.


Kiln Formed Glass, Digital Ceramic Transfer & Stainless Steel


42 x 42 x 6.5 cm