RC Macaulay writes, "Interesting to watch a skilled bricklayer use a " certain" type trowel to remove very old mortar from a used brick. notice very carefully that he strikes the brick near the old mortar and " shazzaam!!" the mortar instantly releases from the brick. Once had an old timer say he had a certain trowel that " sang" when he struck the brick a certain way so he could feel the brick resonate in his hand.and the mortar would release."
Richard, ...and all Vos who are interested in that fine-line between art, skilled-craftsmanship and science... especially as is evidenced in the building trades... and matter of fact - ancient building trades, going back centuries. I lived for a while in San Miguel de Allende in central Mexico, and can attest to one of the most amazing and relatively unknown skills in bricklaying... a skill and a beautiful end-result that literally has to be seen in order to be believed. Unless you have seen these brilliantly constructed dome roofs which are common everywhere there, from middle income houses up -- and this is in the middle of very active earthquake and volcano zones, then you will think that my description of how they are built is some kind of "fish story." Some of the Colonial buildings, which are all over the highlands of central Mexico are over 400 years old and have withstood earthquakes in the mid-8 range - yet they are shallow domed roofs going up many floors - called "boveda" ceilings and made from local brick and mortar according to ancient recipes with no reinforcement whatever. I did a quick google and found some images at the bottom of this page. http://www.vrbo.com/13340 OK that part about shallow unreinforced brick domes is believable, as domes and arches are inherently strong, even shallow ones made of brick - especially with thick adobe walls to carry the downward stress. But here is the kicker. These domes are built, layer on layer working from the 4 corners of the room (only works with 4 corners) to the center in thin layered stacked arches (large rooms, some over 1000 sq ft) and get this... NO FORM whatever is used !! The bricklayers (bovedistas who start doing this when they are pre-teens) work fast in teams of 8-10, standing on flimsy scaffolds, using no wood or other form under the dome to hold the advancing brickwork, but have developed from ancient times this very tacky glue-like mortar which has to be mixed in small batches continuously a few kilos at a time and then used within 5 minutes or less... it is all natural, not very strong except in compression and dries instantly. The mortar has a special name I can't recall but is mostly composed of "cal" (their name for the local lime .... which BTW gives California its name- i.e. lime-kiln) and this tacky mortar will hold an advancing row of unsupported brick against gravity on a very slight angle long enough for the whole-layered-arc row to be put in place over ten minutes or so - after which it holds on its own, as an nearly flat arch... but prior to that you have all these bricks pretty much suspended in space held by the gluey cal - it has to be seen to be believed. OK that's my building-trade-tale for this date but it's no April-fools joke either... the scientific 'angle' in this is that there must be something in the local limestone which provides this amazing gluey property .... quien sabe? Jones
