...more limewash advice

[fieldfare]

Hi folks, another limewashing question unfortunately :lol: Thanks for the info re. the wet wall- have abandoned this for the time being. We are currently trying to white limewash (white)a previously limewashed internal wall (mid blue). Apparently we have bought some really pure limewash but it is having a few problems in coverage (i.e. the blue still shows through after a couple of coats). I get the feeling in certain parts of the house that carbonation is taking about 5 days- is that 'normal'?

1) Is 'purer' limewash likely to carbonate slower?

2) Could we decrease the purity/thicken it up by adding some lime putty?
3) Wait until the temp. increases? or just wait longer b/w coats- we have no heat in the house and outside temps are fluctuating b/w -1 to +10 degrees C. Are we just torturing ourselves by trying to do it in these conditions.
4) Would you always dampen a wall prior to limewashing? Even in cool, 'slow-evaporation' conditions?


Thanks!

 

[Gervase]

The biggest factors affecting carbonation are dampness and temperature.
Below 5 degrees C, the reactivity of the free lime seems to go into a coma, and carbonation can take ages. And, as you've already found, if the stuff stays wet (rather than merely moist) it won't carbonate. That said, you should still dampen down the surface before applying limewash, just in case it's so absorbant that it strips the water out immediately.

Your five days is quite normal - in fact it can take longer. And, until you've got a couple of coats completely carbonated (for which allow a couple of weeks in current conditions) you won't know if you've beaten back the blue.

 

[Mark]

limewash is just lime putty and water, making a thicker mix up wont help - it will make things worse I think, plus you might get flaking.

Not sure about impurities, but lime mortar is said to set quicker with impurities so I suppose maybe?

I think that as Gervase says, the low temps and dampness are doing you no favours.

 

[ajbaker]

As has already been said, humidity/dampness and temperature have the most affect on the carbonation process. I recently had a ceiling plastered - with no heating after a week it was still very soft. With the introduction of a little heat (about 10 degrees) it was a more familiar process over a few days.

There is nothing wrong with 5 days, but if it is taking longer you may want to consider a gentle heat source if only for a few hours a day.

The limewash I have been using has been a 1:1 mix of putty and water. By all account this is very lime rich. I can testify that coverage is not improved by adding more putty - it took four coats on a newly plastered internal wall, and still I feel patches warrant another coat.

If you are trying to cover a deep colour (blue) I would recommend you persevere, and have 4 coats on before deciding if it is going to work. Another factor is that until completely dry the limewash will appear translucent and therefore show the blue. More time and more limewash I think.

Another possibility is a breathable paint? I am about to paint my room with one of the emulsions from NBT. http://www.natural-building.co.uk
This should cover in one coat and is relatively cheap from http://www.mikewye.co.uk

Let us know how you get on.