Tag Archives: lime mortar

Novel micro-images of lime mortar destruction by frost weathering

Frost is here again and thus weak building materials are at risk, for example traditional lime mortars applied during the last summer season. Over the last few days I was able to observe frost heaving in a lime mortar that has not properly hardened/carbonised due to recent rainy and moist weather. As far as I know, no one has previously documented such ice crystal growth, on a micro-scale. The phenomenon is akin to frost heaving in a soil profile: The force of growing ice whiskers lifting the uppermost parts of the soil. Continue reading

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Taken by the frost! The beauty and destructive force of ice growth on masonry

After 29 years of working with weathering of cultural heritage, I have finally seen it “live”: How the force of ice can destroy plaster on stonework. It is more diverse than I though. A complex and fascinating world of beautiful … Continue reading

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Frostforvitring på kulturminner: Bilder av et fenomen få har dokumentert og formidlet

Mange har meninger om frostforvitring på kulturminner, på stein, murverk, puss og mørtel. Men det er få som har dokumentert fenomenet med bilder. Derfor er det mye synsing om «isens ødeleggende kraft». Her presenteres nye fotos av hva som faktisk kan skje når kalkmørtel blir offer for frost. Det dreier seg bl.a. om islinser som dannes og vokser i eksisterende svakhetsplan og sprenger biter bort. Stedet er den nye, «middelalderske» kalkovnen i Kvernsteinsparken i Hyllestad i Ytre Sogn. Continue reading

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Burning the beaches. Happy New Year from the Faroe Islands!

The Faroe Islands, in the middle of the North Atlantic Ocean. Basalt and other volcanic stone everywhere! Yet, many buildings on the islands were erected by the use of lime mortar, from the Middle Ages on. There is absolutely no limestone on the Faroes. Thus, lime mortar had to be produced by “burning the beaches” – collecting shells from beach deposits, stacking the shells above a fire in a field kiln – and let it happen: Hold the temperature at some 900 degrees centigrade for a couple of days, and out comes quicklime to be mixed with water and beach sand for the mortar. Continue reading

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HOTMIX! Nybrent Hyllestadkalk leskes og testes som restaureringsmørtel på Stavanger domkirke

Endelig i gang med hotmix! Med lesking og testing av nybrent Hyllestadkalk til bruk i mørtel for restaurering. Som mange vil huske, brant Norsk Kvernsteinsenter lokal marmor i en nybygd «middelalderovn» i Hyllestad sist juni, et prosjekt støttet av Riksantikvaren. Planen er å leske og teste brentkalken på flere restaureringsprosjekter i Norge, bl.a. på Selja klosterruiner og Stavanger domkirke. Sidene jeg regelmessig jobber sammen med kollegaer i Stavanger, har vi nå gjort flere tester på domkirken med George Murphy og Bjørn Idland, som er restaureringsmurere ved Arkeologisk Museum (UiS). Det er ikke lett å leske kalk som er brent på tradisjonell måte. For det vil alltid være halvbrente og ubrente biter i slik kalk. Akkurat som i middelalderen. Vi lesket kalken på tre ulike måter, og det var liten tvil: tradisjonell hotmix ga det foreløpig beste resultatet! Continue reading

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“Nidaros: The Portland Cement Cathedral” (Baker Memorial Lecture)

This week I attended the international conference “Rediscovering Traditional Mortars” in Trondheim. The conference was hosted by the Nidaros Cathedral Workshop and it was part of the annual conferences organised by the British Building Limes Forum and its Nordic counterpart.

I was lucky to be invited to keep two lectures, one on the experimental lime burning in Hyllestad earlier this year, and the Baker Memorial Lecture during the gala dinner. A very great honour to keep this traditional lecture for more than 230 delegates! I concentrated the lecture on the use of Portland Cement during the restoration of Nidaros Cathedral from 1869 on. Read on to get a glimpse of all the problems it has caused! Continue reading

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