I can't believe that the men who created the mortar mix that was used to build Mingary Castle had any idea what a superb job they made of it. That the castle still stands so proud some 700 years later is a testament to their skills.
The problem builder John-Paul Ashley of
Ashley Thompson has is that he needs to do as well as they did, if not better, and that's no easy job as the Mingary mix is unique. After sending samples of the original away for analysis, J-P has spent the last few weeks, like a master chef, brewing up recipes and trying them out. Finally, he's come up with one in which he has sufficiently confidence that he's sent it off to Historic Scotland for them to okay.
As can be seen in the top picture, J-P has tried it out on one corner of the castle, and it's looking good. Much of the work for which it will be used is in re-pointing the walls and, as can be seen from this close-up, it's fairly coarse for that - but it works. It'll also be used as a mortar in the sections of the walls that will have to be rebuilt.
J-P was kind enough to take me round to the dry store this morning to show me his 'kitchen'. It's furnished with huge cupboards in which are kept the magic ingredients. It took a bit of persuasion, but J-P finally agreed to let me have the recipe, so here it is:
Take two parts natural hydraulic lime (in the bags at left in the picture), one part slaked lime putty (in the plastic containers)....
....two parts whinstone (crushed dolerite, left), and seven parts Durham beach sand, which is a fairly coarse sand with shell material included. Place ingredients in a very large bowl, mix thoroughly while adding water, and when the right consistency has been reached, tip out into a wheelbarrow.
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