LOCKDOWN JOURNAL: COVID-19.45 (Keith Ackerman)
Since late March the lockdown has prevented me from going to the quarry in Tadcaster to work on Jacob’s Ladder, a public sculpture commissioned for Beeston in South Leeds.
Jacob ’s ladder is part of BasementArtsProject’s ‘On The Corner’ project; funded and supported by the Henry Moore Foundation, Index Festival of Visual Arts, Yorkshire Sculpture International 2019, Leeds Art Fund and Leeds Philosophical and Literary society.
I spent the first 4 weeks of lockdown unwell with what our GP says was almost certainly Covid-19. It was unpleasant, but as my strength returned it felt wonderful to be able to start carving again. My first project was to carve a small sculpture out of Bardiglio alabaster as a 60th birthday present for my brother. More details of that process can be found on a Lockdown Journal posting at: https://www.basementartsproject.com/studio-journal/2020/5/17/lockdown-journal-covid-1938-keith-ackerman
The quarry is still shut (at the moment planning to open part-time early July) so I thought I could use the time to get better at glass casting. One of the many things I love about carving is having a very intimate control of the process but with the casting process I have much less control. So, I thought that I would use the time of forced inactivity during lockdown to try and make glass casting a process that I had more control over.
I am using the “lost wax process” a technique developed for bronze casting over 5000 years ago . I will attempt to briefly outline this complex and wonderful process: Firstly you produce a wax of the sculpture you want to cast. The wax can be made by directly carving the wax or as in this case in a mould taken from the stone element of the triptych:
Wax of sculpture to be cast with funnel and air vent (sprue) attached
The next stage is to surround the wax with special plaster mix which can withstand high temperatures (investment) to make a mould. The wax is then steamed out of the mould leaving a sculpture-shaped hole for the glass to flow into.
The correct volume of high quality billet glass required to fill the mould is calculated. This billet glass is low lead glass in large blocks which improves the clarity of the cast as compared to leaded glass in small pieces. The glass is then placed in a container with a hole in the base and positioned above the mould. My initial attempts used a Heath-Robinson arrangement of kiln furniture and a programme set by the Cromartie technicians when they installed the kiln:
Mould part way through the process of melting
These casts worked but were flawed. Lockdown gave me the time to research glass casting more thoroughly. I bought some new kiln shelves and props so that the setup in the kiln was more stable and hence safer (see photograph below). I taught myself to programme the kiln controller. To produce the optimum clarity in this type of glass I programmed the hold temperature, at which the glass flows into the mould, to 830 deg C as opposed to the 850 deg C it was in the earlier programme. The research suggested monitoring the kiln at critical points by opening the kiln door briefly and looking into the kiln to check that a) the mould was intact and b) that all or most of the glass had left the container and entered the mould.
View of the inside of the kiln showing the pot containing the billet glass balanced on kiln shelves above the mould
I have never opened a kiln at 830 deg C and was terrified to do so. However I was surprised to find that when I very briefly opened the kiln door I was not blasted by a fierce wind of hot air and the kiln temperature only dropped by 10 deg C. This ability to visually monitor the process made it feel significantly less arbitrary in that I could now stop the firing if the mould cracks or vary the melt hold timings to ensure that the mould fills. Until now I had to rely on hoping that the mould held and that my calculations of the hold times were accurate. A reliance that made the process feel potentially hazardous and unreliable.
So a combination of more a stable kiln setup, being able to visually monitor the process and a growing understanding on the effect of temperature on glass flow is starting to give me a greater sense of control of and hence involvement with the casting process.
The firing worked better than I had hoped: the mould and glass container held, the mould was full of glass and the cast had a wonderful clarity. I was thrilled.
The way the cast appears to capture light meant that, as I had hoped, it could form the final element of the triptych I began in 2013.
Kiln view at the end of the firing showing the new shelves and a thin strand of cooled glass remaining from the flow into the mould
There is another element that adds poignancy to my learning of glass casting. I am using my mother’s 47 year old Cromartie kiln which I inherited on her death. I had learned about and enjoyed doing glass casting while studying sculpture at York college. Just prior to Mum’s death we had discussed me learning to use her kiln for glass casting. Following Mum’s death I arranged for Cromartie to service the kiln and fit computer controls to it. Amazingly they had spare parts for this old kiln
The emotions surrounding my Mum’s death prevented my using the kiln, it felt too much her kiln. After a year or so and following encouragement to start to make it “my kiln” I began to use of it. I did a couple of test glass casts (as described above). It was a profoundly moving experience; it almost felt like talking to Mum to be using her kiln and kiln furniture so familiar to me from watching her work as a potter.
This lockdown casting has another link with my Mum, in that I discussed the design for this triptych while sitting with her overlooking the sea at Runswick Bay in September 2013.
I had bought a bronze rod to carve. The idea of direct-carving bronze came from seeing some small sculptures Henri Gaudier-Brzeska had direct-carved in bronze in 1914. Until then I had thought that the only way to make a bronze sculpture was to cast it.
Mum suggested combining the curves of some of my work with the steps in other pieces. The rod provided the curves; I would carve the steps into the bronze. I went on to carve the resulting design in bronze, a very difficult task, as it is so hard.
Over the following year I carved a stone version from a turned cylinder of Zimbabwean Serpentine and made a glass version to form a triptych:
Carved bronze, turned and carved serpentine, cast glass with burnt wax (85mm x 65mm diameter) on Ancaster limestone plinth
The glass cast had black objects floating in it which were produced by wax not fully removed from the mould being burnt during the glass firing. The serendipitous black objects floating in the glass reminded me of objects floating in space. It was only during lockdown, as described above, that I had the chance to cast the “space without objects”.
The triptych now gives me a sense of the stages of matter in space, going from Dark Matter to light. As I understand it Unified field theory is an attempt by physics to explain gravitational and light waves in one theory, hence the title.
Dark Matter to Light [an exploration of Unified Field theory]. (2013 to 2020)
Cast glass, cast glass with burnt wax, turned and carved serpentine all ( 85mm x 65mm diameter) on Ancaster limestone plinth
Keith Ackerman | June 2020