Lime part 5. Finishing off.

DSC_1801Finishing off this series on lime (which has to be said is offered as more of a reference) I will describe the use of hydraulic lime and the overall effects the calcitherm system has had on the house

With both presses sticking the boards on is easy using the calcitherm glue. You can mix by volume/weight but I did it by consistency in small batches. (The glue sets fast only mix what you need.) The boards stick on easily although using calcitherm glue to seal the joins between boards can be time consuming. The boards are easily cut with a saw (careful they are fragile and can snap), but you do not want to breath in the calcium silicate powder.  If joins are not flat and if lumps of glue poke out gently use sandpaper to improve the surface.

The next job was to skim a thin layer of hydraulic lime plaster onto the boards. This is scary since you will see this. Hydraulic lime is made from limestone with clay impurities in it.  This ensures it sets underwater (and that it keeps longer unused in the bag).  The reason I used this was that it was recommended by my local lime supplier as it was very fine.  I skimmed a hydraulic lime layer on by trial and error using a steel float and large decorating spatulas. With all these types of materials they say you should sweep the tool upwards. They also say you should do put two layers of a few millimetres on. I found one to be enough. I also found its easier the thinner the layer of lime you skim on.  Again as above my workmanship is far from perfect, but only when you shine a bright light directly on it can you see its imperfections.

The final bit of finishing off is to paint the lime (this the only reason to add it to cover the calcitherm boards). On the downstairs press I used breathable clay paint. This is not as breathable as limewash. The paint looks good when fresh and is easy to apply but tends to discolour going brown.  On the upstairs press I used limewash which is a kind of thin paint made from lime with added mineral dye.  This has the consistency of cream. I requires multiple layers (>5 in my experience) and good wetting of the surface before and for many hours after its application. I found using a small paint roller was the best way of applying it (note they say this cannot be used for paint again).

Has it worked? Aesthetically both presses look great – at least from a distance.  In terms of usability as shelves, the downstairs one works fine, the upstairs one seems mostly OK.
The downstairs one did not noticeably make the house more breathable.  The effect of the upstairs one has been dramatic.  The whole house is less damp (including downstairs), which is very surprising given the small area of the press (less than 2m2). With an external temperature of less than about 8 degrees C our windows would be covered in condensation, this has almost completely disappeared and when its there in rooms with doors closed at night it dissipates quickly once they are left open in the morning. We have had some Aspergillus niger on the bottom of the upstairs press. This should not happen since the lime is very alkaline.  Hopefully this is just that I had not put enough layers of lime wash on. I am adding some more.

I would thoroughly recommend the calcitherm system.  The only problem is the expense which makes its affordable for small areas rather than the entire outside wall of your house.

Neil

 

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