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Old July 27th, 2017, 05:27 AM   #5981
qjone2
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Originally Posted by keepthepast View Post

The earlier photo shows a facade that looks pretty fantastic with limited darkening. Could it have been different stone with different composition properties? The old/surviving buildings in Dresden are almost totally black--Kreuzkirche, Dreikonigkirche, Martin Luther Kirche, etc.
I've seen other old photos where it looks much darker – I think the light is just bringing out the warmer tones of the facade, but yes, it is very clean. From what I can gather, it too is built from sandstone, but obviously Elbe sandstone oxidises much more quickly. If, say, the Kreuzkirche or Hofkirche were to undergo similar treatment, I doubt very much they would be quite so pale. A few shades darker than the Frauenkirche is currently I'd reckon – warm yet still rustic looking.
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Old July 27th, 2017, 10:40 AM   #5982
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It is in fact a different stone. The old foto shows white stone that is just dirty. Thats definitely not the case in Dresden. You can of course clean the sanstone an make it bright again, but it will turn black after a few years. So it doesnt make sense at all.
Sealing the stone doesnt help either. They tried this with several sandstone buildings during the 70's and 80's and prevented the drain of water.
Sandstone is a porous material that evaporate a lot of water. If it stays wet you get freezing damage and the stone will turn into sand.
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Old July 27th, 2017, 10:51 AM   #5983
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I've heard conflicting reports that the Frauenkirche has been sealed and should not turn black as with other sandstone structures in Dresden. Is this true?
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Old July 27th, 2017, 11:14 AM   #5984
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No, the whole reconstruction idea was that the stone will turn black an the signs of destruction will diminish.
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Old July 27th, 2017, 12:34 PM   #5985
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We have to keep in mind that different factors such as structure of the building and the used sandstone influence the process of blackening. The Frauenkirche is a perfect chance to observate such a process. Looking at the building, one can clearly recognise the parts mostly affected by weathering.



The cupola and the part where the building "rises" to the dome. Mostly called "Kuppelanlauf" in German, don't know the proper english word for it. In contrast to the cupola, the rain and snow hit the sandstone almost horizontal and can not drain off fast from there. That was always a problem of the old church because water percolated inside. (They managed it with a special laminated underconstruction for the new church)

At rain it is very good visible.


https://www.tag24.de/nachrichten/dre...spenden-197595


So unsurprisingly, these exponated parts will blacken much faster than other parts especially of the straight walls. I doubt that we will see significant changes there the next 20 Years.

The Zwinger has undergone major renovations and rebuildings since at least its partial destruction during the revolution 1848/49. Only a minority of its statues and decorations are originally baroque. The existing and more or less well preserved originals are rather the models for reconstructions which take place continously. That some parts are more or less blackened is again due to different affection of weathering and of different types of sandstones. For sculptures they use a more soften type of sandstone which is more affected by oxidation than harder types.
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Old July 27th, 2017, 02:10 PM   #5986
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Also, the affects of coal and wood burning furnaces contributed heavily to the blackening process, both of which are no longer used. So this change will also help delay/reduce the blackening compared to former times.
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Old July 27th, 2017, 03:40 PM   #5987
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Same with copper roofs. Several decades ago the oxidation process took a lot less time to achieve the desired green patina. Within roughly 20 years a roof/dome turned light green. Now it takes twice the time, if not longer, because the environment is actually much cleaner and there is less acid rain.
They sometimes now fake or try to significantly accelerate oxidation with elaborate methods.
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Old July 27th, 2017, 06:20 PM   #5988
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^
Which looks awful IMO.
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Old July 27th, 2017, 07:44 PM   #5989
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Quote:
Originally Posted by Tolbert View Post
It is in fact a different stone. The old foto shows white stone that is just dirty. Thats definitely not the case in Dresden. You can of course clean the sanstone an make it bright again, but it will turn black after a few years. So it doesnt make sense at all.
Sealing the stone doesnt help either. They tried this with several sandstone buildings during the 70's and 80's and prevented the drain of water.
Sandstone is a porous material that evaporate a lot of water. If it stays wet you get freezing damage and the stone will turn into sand.
Well, Frauenkirche is 12 years old now and it's just starting to turn black, I assume it will become completely black in 20 years or something, so I wouldn't say cleaning the stone on other buildings doesn't make sense, the blackening process is now much slower.
I also read somewhere that they now treat buildings in Dresden so that they don't turn black again, I think it was actually Zwinger in particular, but I was sceptic about it. IMO, buildings should be cleaned, who knows, maybe in a couple of years we'll have good methods of preserving the stone from blackening.
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Old July 27th, 2017, 09:07 PM   #5990
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I think I've heard or read that the sandstone of the Frauenkirche was treated to prevent the oxidation and consequent blackening of the exposed surface. So the old parts which were retrieved from the ruins and the angle non been collapsed, will always, or for much more longer time than normal, be recognizable. Can anybody confirm this fact?
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Old July 27th, 2017, 10:35 PM   #5991
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No. The Frauenkirche is made of normal sandstone, it's not painted or anything like that.

I know that they developed a painting for the Zwinger which avoids the catastrophic effects of oil paints which were used at the end of the 19th century and onwards.
The Frauenkirche has far less detailed structures which are intended to stay visible in the Zwinger. Anyway, what means "normal than longer"? There is no clear formula about how long such a process will take. The old church was built with sandstone from many different quarries of the region, some of these blackened faster, othes slower, depending on the consistency. The church was never completely bright or completely dark but always dappled. For the reconstruction they used sandstone from only one quarry of the highest quality and density. So yes, this stone will, under normal circumstances, take a bit longer to turn black.
Still that doesn't mean, that there are no renovations taking place. Weathered sandstone has much larger problems than its black colour. For example salt efflorescences which are the reason for the current renovations at the largest original fragment of the chuch.






source: http://www.mdr.de/sachsen/dresden/fr...salzt-100.html
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Old July 28th, 2017, 01:10 AM   #5992
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What I argued was not a painting, but a chemical treatment which slows down the oxidation process without altering the stone's composition and without stopping it at all. But, again, I only have a faint memory of that. No problem if I'm wrong. And of course, what I think to remember is at the end only the choice made of a certain type of sandstone which naturally resists better to the process, as You suggest.

Last edited by pccvspw999; July 28th, 2017 at 01:18 AM.
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Old July 28th, 2017, 10:36 AM   #5993
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There is just no way treat any material with chemicals, without altering the composition of the material. Thats the basic element of chemical treatment
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Old July 28th, 2017, 10:57 AM   #5994
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Until the 1850`s all Sandstone surfaces where painted with a paint/sand mixture of that same sandstone colour. After that time, for the first time in Europe, stone was left the way it was. Today we blast the stone clean. Between 1850 and 1990 the stone darkened very, very fast because of the bad air quality. That is why cities grow to where the wind was coming from to south/west. Anyway, if it is true that sandblasting takes to much surface off, we should do like the we did in the old days before 1850.
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Old July 28th, 2017, 07:10 PM   #5995
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Quote:
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There is just no way treat any material with chemicals, without altering the composition of the material. Thats the basic element of chemical treatment
"...of the surface layer...", to be more exact.
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Old July 28th, 2017, 07:17 PM   #5996
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Quote:
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Until the 1850`s all Sandstone surfaces where painted with a paint/sand mixture of that same sandstone colour. After that time, for the first time in Europe, stone was left the way it was. Today we blast the stone clean. Between 1850 and 1990 the stone darkened very, very fast because of the bad air quality. That is why cities grow to where the wind was coming from to south/west. Anyway, if it is true that sandblasting takes to much surface off, we should do like the we did in the old days before 1850.
The system "before 1850" was awful, it homogenized the natural venation of the stones, and after a couple of years the "painting" began to esfoliate leaving the stone exposed, but adding a "scrap" effect, which made everything worse.
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Old August 3rd, 2017, 10:24 PM   #5997
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The black and white photo appears often, and taken from very slightly different angles, but at different months/years. In the photograph above you can see that the rubble has been cleared away from the streets and pavements, where as other photos show rubble still piled up on the pavements at the base of ruined buildings. Just wondering, how soon after the terrible February air raids did the Dresdeners begin clearing away the rubble? Another photograph dated 1949 shows most of the ruined buildings totally removed, so the clear up must have been fairly rapid in some areas of the city.
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Old August 3rd, 2017, 11:46 PM   #5998
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Clearing of (main) streets started immediately after the Attacks as the dead had to be recovered from the cellars and buried or burned. But the rubble wasn't removed but simply shifted aside. Organised removal of the ruins and rubble started in 1946 with the first of six Trümmerbahnen ("rubble trains") built in Johannstadt. Large scale removal (Flächenenttrümmerung) then really began 1948/49 which produced the empty scenes known from pictures. The Seevorstadt was among the first quartes completely cleared.
They officially finished in 1958 with the last Trümmerbahn removed.
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Old August 4th, 2017, 01:45 AM   #5999
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Quote:
Originally Posted by rudicantfail View Post
The black and white photo appears often, and taken from very slightly different angles, but at different months/years. In the photograph above you can see that the rubble has been cleared away from the streets and pavements, where as other photos show rubble still piled up on the pavements at the base of ruined buildings. Just wondering, how soon after the terrible February air raids did the Dresdeners begin clearing away the rubble? Another photograph dated 1949 shows most of the ruined buildings totally removed, so the clear up must have been fairly rapid in some areas of the city.
I cant be sure in this instance but most cities seemed to begin clearing rubble from streets the morning after air raids.

Also , that image is just heart breaking. Not least because of the architectural losses, but theres just something so sad and eerie about.
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Old August 4th, 2017, 02:27 AM   #6000
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Also, that image is just heart breaking. Not least because of the architectural losses, but theres just something so sad and eerie about.
The statue pictured is the 'Allegory of Goodness" on the Rathaus tower. I think it ties the whole picture together because it is whole, it remains, amongst the ruins – bits and pieces of former things. It, despite being inanimate, plays the role of the observer in the absence of any actual people. In that sense, it personifies the victims - not those who died, but those who remained and were forced to merely watch as their familiar surroundings and, in many cases, their lives, fell apart.

I'm reminded of this passage from Kurt Vonnegut's Slaughterhouse-5:

"It wasn't safe to come out of the shelter until noon the next day. When the Americans and their guards did come out, the sky was black with smoke. The sun was an angry little pinhead. Dresden was like the moon now, nothing but minerals. The stones were hot. Everyone else in the neighbourhood was dead. So it goes.

The guards drew together instinctively, rolled their eyes. They experimented with one expression and then another, said nothing, though their mouths were often open. They looked like a silent film of the barbershop quartet.
'So long forever,' they might have been singing, 'old fellows and pals; So long forever, old sweethearts and pals—God bless 'em—' "

War is horrible.
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