Conservators can take themselves too seriously and sometimes cannot see the wood for the trees. In that sense they are a little like archeologists - the clay sticks to their feet.
A well established conservator friend of mine was sent to the South Coast to try to cure an efflorescence problem in the lime plaster of a little medieval church very near the sea. Sometimes plasters will grow white, fluffy excrescences over the surface which are the result of salts in the mix crystallising as the water evaporates on the outside. This problem is notoriously difficult to cure, and can usually only be controlled by hacking off the old stuff and putting on new - not an option in this case.
They spent a few weeks at the church trying various remedial techniques, but with the absence of a damp-course in the masonry and the impossibility of installing an air-conditioning system in the old place, it was obviously something they would have to live with.
When they analysed the mortar they found that it was almost saturated with salt. Usually you may find traces of salts which have been sucked up from the ground by the walls, but this stuff could have been sprinkled on a boiled egg for breakfast.
Then they did a double-take between the immediate surroundings and the church. The realisation dawned. The medieval builders had simply gone down to the beach and dug the sand they needed at low tide.
Making expensive and time-consuming laboratory tests for analysis is part of the process when replicating ancient mortars. This same friend once sent a sample to a university lab who came back with a detailed description of all the constituents except one. It had a strange and complex component which - after a great deal of investigation - came back identified as 'floor sweepings'.
The masons had emptied the ashes from a wood fire into the mix as was traditional, but being a little short they just swept the floor of the yard and chucked that in too to make up the measure. Like the sea-sand on the beach, it was just close to hand.
Well, now, your explanation has answered a question for us. On the first floor of the house, we have the 'efflorescence' you speak of behind the plaster (leaching through, though) over the chimney and on the front of the brick fireplace. We assumed that it was caused by moisture. We replaced the whole roof, and reflashed the chimney and capped it too. It continues. This gives us another direction to explore.
ReplyDeleteIt will be coming from whatever is behind the plaster.
DeleteWe plan to rip that down next. We wanted to be sure that the leaking problem was solved. I'm going to guess that it must be the mortar between the bricks on the chimney, since the front of the fireplace has the same problem. We have been looking at it as a moisture problem. Looking at it as a salt issue changes it up a bit. Interestingly enough it doesn't seem to affect the plaster of the fireplace on the second floor directly above it which uses the same chimney.
DeleteIt could be the mortar or it could be the bricks. It could be what has been burned in the fireplace. We call 'first floor' one floor up from ground. Is your 'first floor' on ground level?
DeleteAnd do you have a basement below ground level?
DeleteYes. stone walled. 1/2 of it has dirt floors. The fireplaces are on the north side of the house and there are only two, on the first (ground) floor and in one bedroom on the second floor. It's an old house. And there you've got me again. I considered the damp coming down the chimney from a roof defect. It never dawned on me to think about some dampness coming up from the basement. The chimney to the old unused coal boiler is a different one though. It goes up through the center of the house. In the old days, the kitchen wood or coal stove would have tapped into it, as well as small coal stoves on the second and third floors. At this point, we have two vented gas stoves venting out of it. That chimney does not have the problem. I'll have to do some snooping in the basement. There might a cleanout to the fireplace chimneys down there somewhere. The old coal room is down there. We keep that door shut. (the basement gives me the heeby jeebies.) Tim cleans chimney every year by going up on the roof. We do not use the fireplaces, although the one on the ground floor has a cast iron wood burning furnace insert installed, with double walled stove pipe run up the old chimney. Tim thinks fireplaces are drafty and lose too much heat.
DeleteAh. Now I know the problem. It's evil spirits wafting up from the cellar.
DeleteI KNEW it. Now that my opinion is backed up by an expert opinion, Tim will have to believe me.
DeleteI bet they knew the salt would come out but reckoned it would be someone else's problem. ps I've done jobs like that. I once painted the grubby external stone margins around windows with indoor emulsion to make it look nice to sell the house. It worked.
ReplyDeleteI bought my last car from someone like you.
DeleteFascinating stuff Tom.
ReplyDeleteI only write this stuff to try and keep you fascinated, Weave.
DeleteThe weaver in Australia who I mentioned told me she joined a guild in Canada, and they have been her best source of learning. Which is only to say, information old and new flashes around the new world.
ReplyDeleteYes, the online things are really useful - like watching a You Tube tutorial - but eventually you need hands-on experience.
DeleteMedieval builders improvised a bit causing problems for future conservators. That is some fancy, highly skilled detective/lab work, revealing the original builder's thinking. Mystery solved and solution found is always good.
ReplyDeleteArcheologists don't use their intuition enough. The woman who discovered Richard the Third just had a hunch he was under the letter R painted on the tarmac of a car park in Leicester and was laughed at as a crank until the scientists proved her right.
DeleteI'm with Weave, Tom - absolutely fascinating.
ReplyDeleteMany people would find this boring.
DeleteI suppose this is why we have Building Regulations and the quality of concrete (and claddng) and it's ilk is supposed to be 'safe' these days.
ReplyDeleteThere is historical stuff and there's safety stuff. Two different departments.
DeleteThis has all got me worrying about the foundation on our home which is starting to crack and crumble after more than 100 years.
ReplyDeleteIs your sub structure clay?
DeleteI don't find it boring, some of the old bricks in the church wall are white because of salt. There is a stand of old petrified oak trees in Essex, standing for a 1000 years because of salt. And, that building above looks almost like the Meare Fish House in Somerset, but it isn't!.
ReplyDeleteThat photo is somewhere called 'St**** on the Wall'. I use Essex salt in my cooking... not that we want to start talking about food again...
DeleteYes in a flat I renovated in a concrete building from the 40s, there was a crack on the bathroom exterior wall that had efflorescence, so I got the tiler to grind it back and tile over it. About a year later it will come as no surprise that the tiles buckled. Ah well. Cute flat though - the whole building f 16 or so was sold off as separate titles so lots of people were ding theirs up at the same time and they were all VERY envious that ours had the original pagoda style pelmets on the windows. Um no, my Dad made them for me ;-)
ReplyDelete