Recording the plaster ceilings at Kellie Castle
Transcript
Four speakers: Bryan Dickson (Head of Buildings, National Trust for Scotland); Will Napier (Chartered Building Surveyor); Sophia Mirashrafi (Senior Digital Innovation Officer, HES); Yueqian Wang (Digital Innovation Trainee)
Bryan
The origins of this project really relate to a partnership that we have with Historic Environment Scotland
around using digital innovation to better understand the way that our buildings perform.
We started with Historic Environment Scotland over at the Hill House in Helensburgh.
That's a property that was suffering from damp ingress, and so we were using different forms of digital technology to understand both the effects of that dampness and how that building was drying out.
That involved the use of digital scanning and digital modelling.
With that successful partnership, we decided to develop a trainee relationship, so we employ a trainee every two years.
That trainee learns how to undertake a variety of digital scanning skills and apply them at various National Trust for Scotland properties.
The portfolio of the National Trust for Scotland is really, really varied.
We have in the region of about 15 castles, and some of them have some really significant plaster ceilings.
Castles such as Craigievar, House of the Binns, Fyvie Castle, and of course Kellie Castle here as well.
Will
The plasterwork ceilings here at Kellie Castle are amongst the most significant plaster schemes in Scotland.
Downstairs in the library is one of the earliest surviving 17th-century plasterwork schemes.
What you see at Kellie is an evolution of plaster style through the 17th century.
The digital scanning that the NTS and HS are doing on Kellie Castle is a continuation of recording that's gone back really until the late Victorian times.
In the early 20th century, Robert Lorimer recorded the ceilings here.
He produced the ink drawings, photographs taken throughout the 20th century.
The digital scanning that's taking place today, the future of scanning will take us somewhere else but it's all very important.
Not only are we recording these fantastic schemes and architectural details for us to understand and enjoy and monitor, but it's a continuation of something that's gone back well over 100 years here at Kellie Castle.
What really excites me about this project and the digital scanning is the data produced has great potential.
The level of detail, providing that data is accessible for researchers in the future, it's just limitless.
And I think that that's a fantastic resource to have.
Sophia
The way that a 3D scan works is the machine is set up in a room or a space.
It sends out an invisible laser that then bounces off the wall, and it measures the time for that to happen.
What that does is it captures a point in 3D space and it does that a million times per second in a dome.
That's called a point cloud.
Once that scan is taken, we then move it about the space and we can stitch, using the overlap of each scan, those together and that makes a 3D point cloud in full.
The way that photogrammetry works, which is another method of making a 3D model, is you take overlapping images and stitch them together in a clever piece of software.
With photogrammetry and laser scanning then, we can combine these different ways of making a 3D model
so that we can get a correct, to-scale, 1mm accuracy model with the laser scan data, and then the nice beautiful texture and colouring of the real world, with the photogrammetry on top of that.
What's been really rewarding for both organisations within this traineeship and this scheme
is to be able to explore, to innovate and to sometimes fail, to really find out different methodologies used to capture these sites both in 3D but then also different ways to use them.
Things that we can then take into our everyday workflows within my team but then also the teams at the National Trust for Scotland as well.
It's a beautiful test bed to learn and discover, and also to train the next generation of folk who are looking to come into this sphere as well.
Yueqian
I have been learning the skills to document a place, for example photogrammetry, 3D laser scanning and also 360 photography.
I also learned how to plan for survey projects like this and I gained a lot of skills in 3D modelling by processing all the data we get.
For me personally, I enjoyed my time working at Kellie Castle because I have the privilege to work in such a beautiful environment and I get to see some of the ceilings up close, although through the camera lenses.
Another thing is I get to know more stories behind this special place by doing the research before the fieldwork.
And also I get to test my own ideas about using digital skills and technology to tell the stories behind those ceilings.
Bryan
The National Trust for Scotland holds a wide portfolio of property and we look after that on behalf of the nation, so that we can hand these properties on to the next generation.
Projects like this are really, really important, both to explore what digital innovation can bring but also to help secure the future of these properties.
I recently worked on the Kellie Castle Ceiling Project as a Digital Innovation Trainee, using my skills to document the beautiful yet challenging plasterwork, and discover the hidden stories with 3D digital technology. I embarked on this joint traineeship after finishing my MSc in Architectural Conservation. Working closely with the Digital Documentation and Innovation team at HES, I have been gaining skills in digital documentation through live projects at Trust properties.
Creating accurate digital records for heritage assets has proven to be a useful tool for conservation, engagement and improving accessibility. 3D datasets provide accurate information to facilitate decision-making, connect the wider public with their heritage (especially remote sites) and improve heritage organisations’ sustainability by offering alternative access for staff. In 2019, the Trust and HES, two leading heritage organisations in Scotland, joined forces to demonstrate how we can use cutting-edge technology to protect historic buildings.
Using tech to protect the Hill House
Kellie Castle and its plaster ceilings
Many of the Trust’s buildings are home to richly ornamented plaster ceilings, as at Craigievar Castle and Brodie Castle. Apart from the beautiful designs, the authenticity of fabric and the historic context in which the plasterwork was created is also valuable. Dating back to 1617 and restored by the Lorimers in the late 19th century, Kellie Castle is a notable example of Scottish Renaissance plasterwork. Clues have been discovered that suggest the fashions and craftsmanship from Kellie radiated its influence to other Scottish estates. [1]
Kellie’s interiors were panelled and plastered in the 1600s to establish luxury, as well as celebrate alliances. The library ceiling was made for James VI by Thomas Erskine, 1st Earl of Kellie, who had grown up with the king; the plaster ceiling decorations in the dining room, drawing room and Earl’s bedroom mark the marriages of the 3rd Earl of Kellie, Alexander Erskine.
Through this project, we are working to enhance our understanding of these historic ceilings by applying the latest technologies in 3D scanning and digital visualisation. Using digital innovation we can try new ways to better understand, care for and tell the stories of Kellie Castle.
Digital documentation
For this survey, the digital documentation team consisted of Sophia Mirashrafi (Senior Digital Innovation Officer at HES) and myself. We wanted to digitally document the most prominent plaster ceilings at Kellie. The ornamented ceilings have always been an interesting architectural element to record and study, but this was the first time they have been recorded in 3D.
The primary purpose of the survey was to create a detailed record of the current condition of the plaster ceilings. We chose to combine two types of 3D documenting technology: 3D terrestrial laser scanning and high-resolution photogrammetry. The scan data was used to generate a highly accurate and scaled virtual model of the ceilings, and the high-resolution photos provided a vivid, photorealistic finish.
We also took the opportunity to test and adapt the methods to document the plasterwork in depth. This included improving the methodology in data capture, testing the uses and qualities of various 2D and 3D outputs, and finding new ways to share the data. The learnings from Kellie will serve as a case study for wider digital documentation projects at the Trust’s properties.
To capture in great detail all faces of those projecting profiles high up on the ceiling, we set up the kit at multiple locations and tailored the settings to better adjust conditions of different rooms. The creamy white colour of the plasterwork was a challenge. The ceilings are the perfect canvas for daylight, and their colour can change drastically at different times of the day. To capture the true colours, we treated each ceiling as an individual for photogrammetry and then carefully muted the impacts of ambient light by colour calibration in the office.
Next, we combined all the data we had captured in specialist 3D software. This searches for similarities between photographs, and scans and merges them into 3D datasets. Ceilings with smooth plaster finishes were tricky to process. Some photos looked very similar and were not correctly matched with the scans. In these instances, I needed to manually pin cracks, stains or other sharp defining features against the plain colour of plaster in the software; those points helped the processing software to correctly match the photos with the scans.
Having overcome these challenges, I created scaled photorealistic 3D datasets of six ornamented plaster ceilings at Kellie Castle using the data we collected on site. A set of orthographic views (measurable 2D images) were also created from this dataset. These images record the condition of the ceilings in extremely high detail: signs of discolouration, hairline cracks and powdery edges can be spotted. They are a detailed record of the state of the building fabric on that fixed day.
Links to the Lorimers
When we were planning the survey, a set of detailed architectural drawings created by Robert Stodart Lorimer caught our attention. Robert was one of the best-known architects in Scotland in the early 20th century. Aged only 14 when the family moved into Kellie Castle, Robert seems to have been inspired by the plasterwork – as was his older sister Hannah, who went on to carry out the plaster modelling and painting of William Burn’s ceilings at the House of Falkland.
Find out more about Robert Lorimer’s work
Aged 23, Robert created drawings of some of the most richly decorated ceilings at Kellie. After the data processing, we compared our work with these drawings. It seems that the ceilings are mirrored in his drawings. This interesting discovery provoked us to imagine the documentation methods used more than a hundred years ago – and how greatly surveying technology has evolved today!
Anatomy of a building
Inspired by the views from processing software, we presented Kellie Castle in a way that could only exist in a virtual world. Transparent walls, draped down the ceilings like veils, allow the audience to see all six ceilings at once. Furthermore, a height map was created to visualise the undulations in the library. The minor shifts of the plasterwork accumulated over the centuries can now be measured and meticulously mapped with digital technology.
The history of the master plasterers in Renaissance Scotland lives within the spectacular ceilings we still see today, as well as the techniques and craftsmanship of the Arts and Crafts period in Scotland. We know that it was the skill of local modellers, led by the plasterer and builder Robert Williamson of Pittenweem, that ensured the ceilings at Kellie were successfully restored in the late 19th century.
To celebrate the role of traditional craftspeople in plasterwork, I created a digital model to simulate how layers of plasterwork might have been built in the library. The model consists of timber laths, three coats of plaster, and the decorative casts. You can find more about traditional plastering in the Inform Guide on Lime Plastering.
Improving accessibility
Providing an alternative to physical access at Kellie Castle is another thing we wanted to do. With the oldest part of the building dating back to the 14th century, Kellie Castle has an organic and complicated layout. Some rooms are only accessible through narrow spiral stairs. During the winter season, the site is closed to visitors. We created a pilot 360 tour of Kellie Castle, which can assist visitors in navigating around the castle as well as providing remote access all year round.
Our outputs are not limited to digital content. To provide a tactile experience and further improve on-site accessibility, we used 3D printing technology to make models of decorative plaster casts at Kellie. Reverse mouldings can be made from the 3D prints for creating new plaster casts, looking exactly like the ones at Kellie Castle.
The experience and learning at Kellie will help to shape the Trust’s Digital Strategy, support the conservation of the building, highlight the craftsmanship of Renaissance Scottish plasterwork, and build connections with a wider audience.
Footnote
[1] William Napier, Kinship and politics in the art of plaster decoration, PhD thesis, 2012, p. 272
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