OPC = Ordinary Portland Cement, (spit!! horrid stuff, in the wrong place).
If you don't add OPC to the mix it will not set, especially in damp or exterior work...try it instead of talking a good show! The reasons anyone who does actually practice this craft uses OPC, is because from trial and error they know if a small amount is not gauged (different amounts for different scenarios) it will not set. We think with all our technical babble we know everything, but sadly the opposite is true and a great deal of passed down knowledge that the craftsmen of the past knew is now lost. I do not know how the masons of the past practised their art fully, I do not know exactly how they worked, but I do know from the painful process of error that if I do not gauge OPC into my mixes, I will encounter problems. These mixes are well established and conform to British Standards; hence they are specified a lot. They are also accepted by English and Scottish heritage for use on listed buildings. Do not confuse internal plastering with external stone setting and pointing, because in that case Fat limes are better for plasters without a doubt.
At the end of the day, basically no-one really knows the methods the old masters used, all one has to do is look around and see the arguments for and against this and that. But we all like to stroll around with our noses up in the air thinking we are the bee’s knees, but after looking passed our bigotry we simply do not fully understand the old methods employed.
This is true for many a subject, not just stonemasonry. Take cast iron, well have a look at the old Victorian castings on say a fireplace then compare them to a modern one, there is no comparison in quality. They used to cast these things on the sand banks of the river where I used to live and they would come out crisp and clean, nowadays with all their so-called modern technology, they cannot replicate the definition or quality.
My Tip: Never use OPC, it hurts masonry!
True, if used for setting stone at the same ratio as for bricks and blocks, but if gauged at respective levels for stone masonry it is a tried an tested method.
my fellow Peter Cameron from Historic Scotland at Fort George, there they know the good guys (and give them my greetings).
He would obviously know that the arcade of the cloisters at Iona abbey in Scotland was completely rebuilt using hydrated lime and OPC about thirty-five years ago and is in as good condition as when it was done! The cills, stools, columns, caps and springers including the spandrel rubble are all set on gauged hydraulic lime and I must say are looking good for another hundred years or so. Mugdock castle in Scotland has also been restored in 1985 using hydrated lime and OPC gauged and is looking as good as new.
Only a good shaped pure hydratic lime plaster will work well to use whilst pointing up an old sandstone porch. There are many technical reasons, here are some of them:
I think you mean hydraulic Theoretical waffle. Number one the great craftsmen of the past never bothered with all this nonsense, instead they used the tried and tested method of what works, works and what doesn’t, doesn’t. Most sand was hand drawn from sandbanks (all the good is washed out of modern sand, I can still access freshly dug sand straight out the ground luckily) All the old buildings were built on the fly and everything was carried out on site, there was nothing technical about any of it, they used to add all manner of ingredients to their mortar mixes, it was pretty rough and ready from that point of view. Can you imagine a building site in 1780 with a squad of institutionalised, day-glow office boys prancing around talking b****cks? They did not need droves of these superficial types to build there cathedrals. They just knew their stuff from a practical sense and today the edifices they built stand testament to that and today we could not replicate it using their methods. One important factor is to always make sure the lime is new and has not had time to absorb any moisture before being hand mixed and banked. The best lime mixes are those that are left in the pits or banked the longest, the older the better. I also personally believe mixes using hydraulic lime gain strength as they age. One argument is that cement discolours the mortar, but it is the sand that causes colour change, that’s why local sand should be used if at all possible. In any case you can use white cement which is the same colour as lime anyway and is used on limestone as a matter of cause
A bag of hydrated lime bought at the builder's (Type-S, bagged lime) is quicklime that has been factory slaked only to the point that a powder is formed and not putty. The stuff in this country is high-calcium lime Hydrated lime is dried lime putty, there is no difference when mixed by hand and banked up for a week, there is no technical justification for requiring the use of lime putty for these applications. The reasons architects and others of this caste specify it, is because they do not have to execute it. And do not suppose as architects talk of the prime function of mortar is to bond masonry units into a monolithic mass as true, because it is wrong, a the skills of the mason bonding and tying the stones is what bonds the wall, not the mortar.
The first layer of joint filling mortar should be grained 0 - ~2mm, the finishing 0-~0,8/1mm
Way too fine. Sand this fine should be used for setting dressed stone regardless of the labours to their facings. All one has to do to prove what a silly statement that is, made by someone who I can guarantee has never dressed or set a stone in his life. is go up close to an old building and look at the joints to see the various sized binders that make up the finish pointing, they will be vastly larger than that and of a great range of sizes because if they are not they will not hold together during bad weathers.
spent 1and 1/2 hours removing a metre square section of it.......all these nasty little slaters and undesirable creatures never seen before falling out from behind!
That's what I thought it stood for, but I needed to make sure I understood the jargon...Thanks
The mixes you are talking about are completely different to gauged mixes I am talking about and are applied by dunces who know nothing of their subject. I too have spent far more time than you ever will removing their disgraceful desecrations. But by all means go ahead and do as you please, but you will only do it once.
