A client of mine once told me I was a "compulsive explainer". She was, of course, absolutely right. She used to allow me a minimum of 3 minutes on a particular lime subject whereupon I'd be silenced by an improvised alarm i.e. her going "Beep". So, in keeping with the aforementioned timeframe I'll try and explain - in the briefest way - what I want to explain.
It means reiterating some of what I've already spoken of on previous pages but bear with me. Most of the period stone-built houses in England were never built with lime. They were only ever built with earth mortar. This needed, and still needs to be, protected otherwise it will eventually get washed out.
Low status buildings such as barns, cattle-sheds and outhouses were often left with their earth mortar exposed. Many older low-status agricultural buildings can still be seen with their original earth mortar - as the photograph below demonstrates. It's light brown because it's a mixture of high clay content subsoil, sand and quicklime.
This was taken during a visit to a Grade 11 listed building in Bicester and is one of the outbuildings. As you can see, it's simply earth and lime mixed together to form a viable bedding mortar but when it gets wet it will turn back to mud. Hence the term "mud" is still used in the building trade today to describe mortar.
In order to stop the above kind of mortar being washed out and suffering the impact of mortar bee activity, driving wind, rain and general dilapidation over time it needs to be covered with a flexible porous pointing mortar. In the photograph below this can be evidenced on the house as it is of far higher status that an outhouse.
Although there's a mixture of different mortars in this elevation one can still see the original light coloured lime mortar. It's a functional finish and has simply been trowelled over the tops of the bedding joint before being trimmed up and lightly brushed.
All of the original mortar on all of the stone build property in Oxfordshire and its surrounding areas had pointing mortar applied like this.
On deconstruction it can be seen that there are a number of different sands including fines and sharps as well as an abundant amount of horsehair. We put this is all our hot lime mortars to act as a binder and reduce cracking. As the lime was quicklime it means it would have been applied hot and would have included unburnt and partially burnt limestone. We include this as well. It didn't have to be applied very thickly because it was very sticky and so workable it would fill all voids. It has lasted between 200 and 300 years.
The example below is from a property built in the 1700s. You can see the evidence of historic pencilling.
The thing is, nobody does this. Well, ok, I know of one in person Yorkshire. Everyone else who works with quicklime mortar does a churn brushed finish. It's nice but it's not historic.
So, if you really do want a like-for-like mortar then it can be done. Please be sure to ask for it when you make your enquiry.