<<<copy of reply to forum>>>There should be no panic with the lime plaster - thats one of the problems with it in modern construction, it needs lots of time to absorb the carbon dioxide from the air, when you seal it you stop or least slow down the cure.
Some old time books advise waiting up to year before painting or sealing the plaster. The other problem is that if it is still damp, the alkilinity will effect many modern paints.
The best solution, if you are building a "300 year old" house (designed to stand the test of time - somewhat unusual in Canada and USA), is to make
sure the whole structure can pass moisture somehow - instead of sealing you put on something which makes it easier to clean (soap scum, fingerprints,etc.) without completely stopping the air and moisture. There are many strategies. The ancients would use beeswax, heated onto the surface and then burnished out. They might also use olive oil, which reacts with fresh lime
to form an olive oil soap. What I recommend, and has stood the test of at least 100 years, is a type of "water glass" called potassium silicate (kaosil). This is not the sodium silicate water glass. The problem is that it is available in huge, incredibly cheap quantities or in small, expensive quantities. To see how this works, checkout the website
www.keimmineralcoatings.com. I have had excellent result waterproofing fresco with this solution, and you can mix in your fresco pigments and actually paint concrete and lime plaster with it.
All these solutions are difficult to advise because so much is an organic process, a skill which comes with age and experience, difficult to predict what will happen without seeing the job. Sort of like the old water witchers, or the old pros which can find a leak in a roof many yards away from where everybody thought it was.
Sometimes, like old plaster and old wood, the wear and tear actually adds a beautiful patina to a piece, which modern plastics, paints or glass never
seems to develop. This is the best goal in design.
Lime washes would have to be replaced constantly in a shower stall.
Sorry, I have written this quickly. No problem at all if you have more
questions.\
Gary Waller
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