Per Storemyr Geoarchaeology & Conservation

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

Posted on February 9, 2018 by Per Storemyr

The beautiful micro-world of ice: Whiskers, a peculiar form of ice, growing from tiny fissures on lime plaster at Hyllestad, Western Norway. Width of image c. 2 cm. Photo by Per Storemyr

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 forms of ice growth: Ice needles, ice whiskers, ice lenses. An entirely different thing than statements suggesting that the 9% expansion taking place when water freezes to ice breaks porous materials apart. Although supported by one case study only, what strikes me is the resemblance between ice growth and a more well-known weathering agent: Salt crystallisation – the growth of salt crystals destroying materials. My observations took place over the last few weeks, in Hyllestad in Western Norway, on the masonry of a copy of a historic lime kiln. Continue reading →

Posted in Heritage destruction, Monument conservation, Norway | Tagged frost heaving, frost weathering, Hyllestad, lime mortar, limekiln, Norway, salt weathering, weathering | 3 Comments

The world’s northernmost medieval marble church

Posted on January 27, 2018 by Per Storemyr

Marble arch above the choir window at Gildeskål church in Northern Norway. Photo by Per Storemyr

The small, Romanesque Gildeskål church is one of the most complete marble churches in Norway. It resides at the magnificent coast along the Atlantic Ocean far up north, in Nordland county. And it is, presumably, the northernmost marble church in the world. Together with Giske church further south, it is part of outstanding, but little known, medieval marble architecture in Norway, of which Nidaros Cathedral in Trondheim, with thousands of marble columns, is the most spectacular example. Continue reading →

Posted in Archaeology, Marble, New publications, Norway, Old quarries | Tagged Cultural heritage, Gildeskål, marble, Middle Ages, North Atlantic, Norway, old quarries, quarry | Leave a comment

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

Posted on January 12, 2018 by Per Storemyr

Islinse sprenger ut et flak av en puss/slemming påført i juni 2017 på den nye, «middelalderske» kalkovnen i Hyllestad (Ytre Sogn) i januar 2018. Bildebredde ca. 5 cm. Foto: Per Storemyr

Mange har meninger om frostforvitring på kulturminner, på stein, murverk, puss og mørtel. Men det er få som har dokumentert og formidlet 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 →

Posted in Monument conservation, Norway, Ruins, Weathering history | Tagged frost weathering, Hyllestad, Kvernsteinsparken, lime mortar, limekiln, weathering | Leave a comment

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

Posted on January 8, 2018 by Per Storemyr

Hvitanes "White Cape". Just to the north of capital Torshavn at the Faroes. Grand sea shell deposits that were, presumably, used for lime burning already in the Middle Ages. Photo: Per Storemyr

Hvitanes – “White Cape”. Just to the north of capital Torshavn at the Faroes. Grand sea shell beach deposits that were, presumably, used for lime burning already in the Middle Ages. Photo: Per Storemyr

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 →

Posted in Archaeology, New projects, Old quarries | Tagged Faroe islands, lime burning, lime mortar, limekiln | 5 Comments

Værnes: Norges mest komplette sandsteinskirke fra middelalderen

Posted on December 17, 2017 by Per Storemyr

Dypt inne i Værnes kirke: En 800 år gammel gang i vesttårnet. Sandstein på vegger, sandsteinsheller i tak og gulv. Foto: Per Storemyr

Den er dekorert med elementer av kleberstein og klorittskifer, men ellers er det sandstein så langt øyet kan se: Værnes er Norges mest komplette sandsteinskirke fra middelalderen! Den rager i størrelse og volum av brukt sandstein langt over middelalderbyggverk i tilsvarende stein i andre deler av landet! Her er et sammendrag av min artikkel til boken «Værnes kirke – en kulturskatt i stein og tre» som ble utgitt i 2016 og som nå er tilgjengelig som open-access. Det er Grubleseminaret som står bak, med Morten Stige og Kjell Erik Pettersson som redaktører – og ikke minst Kjartan Hauglid som bilderedaktør! Continue reading →

Posted in Archaeology, New publications, Norway, Old quarries | Tagged chlorite schist, Norway, quarry, sandstone, soapstone, Værnes kirke | 1 Comment

Tusen år med brytning av kleberstein tok nettopp slutt. En historie om mekanisering og globalisering. Og om å gjenoppdage gammelt håndverk

Posted on December 12, 2017 by Per Storemyr

REDNINGEN? Manuell brytning av kleberstein med hakker ved Otta i 1918. Slik brytning foregikk helt opp til 1930-tallet i Norge. Kan man ta denne ganle tradisjonen i bruk igjen? Det er den klassiske metoden for å bryte myk stein – den har vært i bruk for store byggeoppgaver siden de gamle egypternes tid. Fra N.S. Beers klebersteinsbrudd, Grandalen, i drift til 1935. Foto fra NGUs arkiv

REDNINGEN? Manuell brytning av kleberstein med hakker ved Otta i 1918. Slik brytning foregikk helt opp til 1930-tallet i Norge. Kan man ta denne gamle tradisjonen i bruk igjen? Det er den klassiske metoden for å bryte myk stein – den har vært i bruk for store byggeoppgaver siden de gamle egypternes tid. Fra N.S. Beers klebersteinsbrudd, Grandalen, i drift til 1935. Foto fra NGUs arkiv

Det er ytterst vanskelig å skaffe kleberstein til restaurering av Norges middelalderkirker. Til og med avisene har fått det med seg. Ved Nidarosdomen, Stavanger domkirke og i Bergen klør man seg i hodet: Det finnes ingen kleberbrudd i drift i Norge! De har blitt offer for globalisering. Hva er redningen? Kan man lære av hvordan kleberstein ble tatt ut manuelt i gamle dager? Kan man låne kunnskap fra et tilgrensende fagområde, nemlig bruk av kalkmørtel? De gamle bygningene trenger også sårt til god kalkmørtel! Problemet har vært at kunnskap om gammel kalkproduksjon har lagt nede i mer enn 50 år. Men nå produseres det brent kalk som aldri før i små «middelalderovner». Håndverket har blitt aktivt vekket til live gjennom eksperimentell virksomhet. Støttet av kulturminnevernet. Kan vi også vekke det gamle steinbryterhåndverket til live igjen? Til glede for restaurering? Continue reading →

Posted in Monument conservation, Norway, Old quarries | Tagged eksperimentell arkeologi, eldre håndverk, experimental archaeology, historic photos, Kleberstein, Nidaros Cathedral, Nidarosdomen, Norway, soapstone | 2 Comments

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

Posted on October 15, 2017 by Per Storemyr

George Murphy er spesialist på restaureringsmuring. Her tester han mørtel laget fra nybrent Hyllestadkalk på Stavanger domkirke i oktober 2017. Foto: Per Storemyr

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. Siden 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 →

Posted in Monument conservation, New projects, Norway | Tagged experimental archaeology, lime burning, lime mortar, limekiln, marble | 1 Comment

Was Nidaros Cathedral built from stone extracted in a large underground Medieval quarry?

Posted on October 9, 2017 by Per Storemyr

A carved-out, medieval soapstone block still attached to the bedrock. From excavations in the Bakkaunet quarry by Trondheim and Nidaros Cathedral, 2004. Photo by Per Storemyr

Ancient underground building stone quarries are rather common. They are known since at least the Old Kingdom in Egypt, some 6 500 years ago, when fine limestone was quarried underground close to Cairo (Tura) in order to provide casing stones to the Giza pyramids. But underground quarries are, interestingly, quite rare in the European Middle Ages. Apparently, there was no need to start difficult, large-scale underground operations to build churches, monasteries and cathedrals until the Late Middle Ages, when, for example, the underground limestone quarries in Paris and Caen in France started to become developed toward the gigantic network of tunnels and galleries we know today. Thus, it is remarkable that a large underground quarry may have been opened around AD 1200 in Trondheim, Norway, in order to provide soapstone for Nidaros Cathedral, the northernmost of Europe’s great medieval cathedrals. Why? Continue reading →

Posted in Ancient Egypt, New publications, Norway, Old quarries | Tagged ancient stone quarrying, Bakkaunet, Kleberstein, Nidaros Cathedral, Nidarosdomen, quarry, soapstone, Trondheim, underground quarry | 2 Comments

New open-access book: Soapstone in the North. Quarries, Products and People. 7000 BC – AD 1700

Posted on September 27, 2017 by Per Storemyr

Several authors on excursion to the Hana soapstone quarry by Bergen during a book seminar in 2015. Photo by Per Storemyr

Together with lead editor, professor Gitte Hansen at the University of Bergen, I have co-edited a brand new book: On the archaeology, geoarchaeology and craft of quarrying and use of soapstone in the North Atlantic region. Without Gitte, this adventure would never have ended! The book contains 17 papers by soapstone enthusiasts and sums up a research revival that has been ongoing for the last 20 years. Norway is a main focus, where soapstone has been used from the Mesolithic until today, but the book also contains papers on Greenland and the North Atlantic Isles by Danish and British colleagues. It gives brand new insights into many aspects of soapstone, especially on sourcing artefacts by combined geochemical and archaeological methods. Continue reading →

Posted in Archaeology, New publications, Norway, Old quarries | Tagged artefacts, Greenland, Iron Age, Kleberstein, Mesolithic, Middle Ages, North Atlantic, Norway, old quarries, provenance, soapstone | 3 Comments

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

Posted on September 10, 2017 by Per Storemyr

The newly restored choir at Nidaros Cathedral in the 1880s (left) and 1994 (right), before the last restoration early 2000s. All the white calcite crusts are a result of leaching of calcium hydroxide from Portland Cement used in the 1880s. Photos by the Nidaros Restoration Workshop and Per Storemyr.

The medieval choir at Nidaros Cathedral just after reconstruction in the 1880s (left) and 1994 (right), before the last restoration in the early 2000s. All the white calcite crusts are a result of leaching of calcium hydroxide from Portland Cement used in the 1880s, and particularly during a restoration by 1920. Photos by the Nidaros Restoration Workshop and Per Storemyr.

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 deliver 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 →