Till startsida
Sitemap
To content Read more about how we use cookies on gu.se

Renaissance for artisanal mortar

News: Feb 21, 2019


To adapt mortar to new building materials and industrial methods, the content in walls and plaster changed during the 20th century. The change meant that knowledge of historical materials and methods for producing mortar were lost. New research at the University of Gothenburg reveals that historical binding agents and mortar can be produced and used in present-day plaster restorations.

“We need to reclaim this knowledge to care for and preserve historic buildings constructed with other materials than those used today,” says Jonny Eriksson at the Department of Conservation at the University of Gothenburg, the author of the new thesis.

Millennial history

The production of plaster and mortar for buildings goes back thousands of years in Sweden. For a long time, builders made plaster and mortar using traditional techniques, but with industrialisation the process changed.

“The change involved using new materials and methods to make mortar. At the same time the knowledge of craftspeople on how to make binding agents and mortar for bricklaying and plastering in different situations was lost.”

The lack of knowledge first became apparent late in the 1960s because the new mortars were damaging historic buildings.

“For long-term and sustainable maintenance of historic buildings, we need to reclaim knowledge that has been lost,” Jonny Eriksson says. “And this requires collaboration among crafts and professions such as architects, engineers and antiquarians. More craftspeople also need to be trained in research on building conservation.”

Investigations in medieval church

For his thesis Eriksson investigated the formation of shrinkage cracks in plaster. He has studied the feasibility of using mortar mixed with the traditional proportions in use until the 19th century. He conducted his investigations will restoring plaster on a medieval church in Tanum municipality in northern Bohuslän.

“It became apparent that it is practical today to make and use the old-style of mortar. These mortars with a high content of binding agents need to be mixed with newly slaked lime, which is lime that has just been slaked with water,” says Eriksson.

During the 20th century, builders discouraged this particular production process. They thought it produced defects in the plaster. Instead they recommended preparing slaked lime one to four weeks before use.
“This was contrary to fundamental practices in the 19th century, when recommendations called for the use of newly slaked lime. The rationale was that this made the mortar more durable.”

The research results show that the older artisanal mortar with a high content of binding agents can also be made today. It also shows that the mortar can be used for plaster without unacceptable shrinkage cracks or blisters from unslaked lime.

“Our experiences with using these old-fashioned mortars in various construction projects indicates that the mortar has good durability. But the lime needs to be newly slaked when used and not stored after slaking nor processed to be packed in a bucket or barrel for later use, for example,” says Eriksson.

Facts
Slaked lime is produced by mixing lime and water. This releases energy in the form of heat, and slaked lime forms. Depending on how much water is introduced into the process, slaked lime forms as either dry powder or a wet paste. Slaked lime is used in the building materials industry and for water and flue gas treatment.
Wet slaked lime is quicklime that has been slaked with an excess of water so that it forms a lime paste. Normally this lime is stored for some time before it is mixed with sand to make mortar. Storage is done to avoid damage.
Newly slaked lime. Making mortar with newly slaked lime involves slaking the lime before mixing the lime with sand. In other words, the lime is used immediately and is not stored.

Contact:
Jonny Eriksson, associate professor at the Department of Conservation, University of Gothenburg; telephone: +46 (0)31-7869350, mobile: +46 (0)766-22 93 50, e-mail: jonny.eriksson@conservation.gu.se
Photo:
Medieval church, clumping of lime in plaster, shrinkage crack and portrait of Jonny Eriksson. Photo belongs to Jonny Eriksson.
 

BY:

Originally published on: science.gu.se

News

  • Welcome, Rebecca Staats and Maitri Dore, new doctoral students at the department

    [9 Oct 2019] From October, we have two new doctoral students at the Department of Conservation, Maitri Dore and Rebecca Staats. They are part of HERILAND, a pan-European research and training network on cultural heritage in relation to Spatial Planning and Design.

  • New live podcast linking museums' collections with the latest heritage research and global challenges

    [4 Sep 2019] Mummies, DNA and Japan - what's hidden in the box? Together with the Centre for Critical Heritage Studies at the University of Gothenburg, Folkuniversitetet and the Museum of World Culture, a brand new podcast series is launched. It will be recorded with a live audience at the Museum of World Culture in Gothenburg during the fall of 2019. The first event in the series is held September 5th and concerns mummies and the handling of human remains.

  • New leadership at CCHS UGOT and UCL

    [23 Aug 2019] From April 1st 2019 Centre for Critical Heritage Studies (CCHS) have a new constellation of leaders both at the University of Gothenburg and at University College London. In Gothenburg, Ola Wetterberg has taken on the role as Director for CCHS and in London Theano Moussouri as Director for CCHS at UCL.

  • Hidden Site Workshop at Äskhult

    [14 Dec 2018] CCHS cluster Curating the City hosted the second Hidden Site workshop at Äskhult, Sweden, November 29-30, 2018.

  • The Department of Conservation at REKO på Nääs

    [30 May 2018] A popular two day event about craftsmanship, craft, the built environment, and conservation of cultural heritage in a beautiful environment around The Castle of Nääs. The department conservation contributed in many ways to this annual event.

  • Visiting Researchers to CCHS/Curating the City Cluster spring 2018

    [16 May 2018] Visiting Researchers to CCHS/Curating the City Cluster spring 2018

  • We are looking for a lecturer in conservation with specialisation in traditional building crafts

    [28 Mar 2018] Subject area: Conservation with specialisation in traditional building crafts Subject area description: We are looking for a craftsperson experienced in traditional construction methods for a position as a lecturer on the basis of occupational proficiency. Traditional building crafts include in particular wood construction with timber framing, log construction, and other traditional building methods.

  • We are looking for a Senior lecturer in conservation with specialisation in conservation science

    [20 Mar 2018] The position includes planning and implementation of research and methodological development in conservation science, focusing on material and degradation studies using natural science methods.

  • Charlotta Bylund Melin new PhD in Conservation

    [2 Feb 2018] Charlotta Bylund Melin defended her thesis "Wooden objects in historic buildings: Effects of dynamic relative humidity and temperature" in the afternoon of Friday, the 26th of January. After the two hour public defense it did not take long for the examination board to gratefully announce her as a PhD in Conservation.

  • Kristina Linscott, the new Ph.D. at The Department of Conservation

    [22 Jan 2018] After a well performed defense of her thesis "Interpretations of old wood - Figuring mid-twelfth century church architecture", which occurred Friday afternoon the 15th of December 2017, Kristina Linscott got her Ph.D. in Conservation. The opponent at the disputation was Associate Professor Alessandro Camiz, Department of Architecture, Girne American University, Karaoglanoglu, Kyrenia, Turkey.

More news

Page Manager: Henrik Thelin|Last update: 6/28/2018
Share:

The University of Gothenburg uses cookies to provide you with the best possible user experience. By continuing on this website, you approve of our use of cookies.  What are cookies?