Limewash produced strong smell of Ammonia

[finn]

Hi again,

I posted a few days ago about the best method for limewashing old ceiling beams that we thought had been blackened in a long-ago house fire. Anyway, after giving the beams a good brushing down, we tried to wash them with water and sugar soap. After about five minutes, we realised that it was pointless. There seems to be some sort of dark, very
soluble coating on them that's impossible to really clean away. It is so concentrated that no matter how many times we sponged and rinsed, there was always more there and the wood looked no cleaner. So we gave up and dedided to put limewash (2:1 of water to Lime Putty) straight on to a patch of it, to see whether it would cover it after multiple coats. When the limewash went on, there was an immediate, overpowering smell of ammonia (to the point of making our eyes water). Does anybody know why this happened ? We think that the beams must have been painted with something that reacted violently with the limewash, but we just don't know what...........Any suggestions?

Hi again,

I've been googling to see what I can find out, and stumbled on a web page which says that:

"Acidic solutions capture ammonia, alkaline solutions allow it to leave."

And the higher the pH, the greater the conversion of ammonia into a gas form. I also read in the forum's archives that oak beams were traditionally fumigated with ammonia as a way of preserving them, so wondered if this was the case with our oak beams. The only catch being that they look as if something was painted onto them rather than just fumigated- does anyone by chance know of a traditional wood preservative like this that would have darkened the wood and contained ammonia?

 

[Penners]

I'm no expert, but I have never heard of oak being painted with ammonia as a preservative.

"Fuming" oak in an amosphere of ammonia vapour is a well-known way of darkening its colour - and I assume this would also tend to kill any little visitors living inside the wood, but I don't know how much ammonia this would actually leave within the wood. I can't believe it would amount to much.

 

[middi]

uioHi. Oak beams in period houses were naturally fumigated by default due to centuries of smoke wood fires, coal fires,soot, tobacco smoke and, as in you case, proper fires charred surfaces , all acidic accumulation of grit with possibly an intermediate coat of of "tarry" product in between or over the top. Anything is possible.

Cleaning these kind of beams will test anybody's elbow power. As to what to use to remove the "unknown gunge" it is difficult to say.

From an ideallic conservation point of view you should leave them as they are, warts and all, in this way historical "fabric" is preserved to tell the tale.

(I agree, we don't live in an ideal world)

 

[finn]

Thanks for your replies. The problem with leaving them as they are is that (a) they're very dark, (b) they're a bit smelly, in a sooty, tarry kind of way and (c) strangely, they tend to get a bit mildewy looking. We're in the process of restoring the house, which is not heated yet, so we presume this is why. We have a breathable, Leca/Limecrete floor (which is excellent, by the way) but naturally there's a certain, small amount of evaporation onto the beams in this room. Funnily enough, the other ground floor room has modern beams/joists, and they never show any signs of mildew/mould. We think that whatever's on the old beams seems to make it prone to mildew. Don't know why though.....

 

[MdB]

Just found this: http://www.css.cornell.edu/compost/odors/ammonia.html (to do with composts) which states:

Another factor affecting the magnitude of ammonia volatilization is pH. NH3 (gaseous ammonia) and NH4+ (aqueous ammonium ion) are in equilibrium at a pH of about 9, with higher pH's forcing more NH4+ into the gas form that you can smell. Thus ammonia is rarely noticed if the pH is acidic , and adding lime to a pile will increase the ammonia odor.

It looks like (in my very inexpert opinion) that if you have ammonia present, adding lime will make it smell worse.

 

[finn]

That's what seems to be happening, but I wonder if it's a temporary thing- if once the ammonia has been released as a gas, whatever is on the beams would then stabilise to the point where we could limewash them....If not, we might have to consider painting the beams instead, which would be a pity.

 

[Lime]

In many older houses dangerous chemicals often lurk in wood, paint even wallpaper.
While left alone they usually do no harm but disturbing them or removing them exposes the operator to potential danger.
As there is no telling what has been put on these beams before (and you can bet your bottom dollar several "treatments" have unnecessarily been applied to these beams) you need to treat them with care.
Ammoniacal copper zinc arsenate, ammoniacal copper arsenate and Chromated copper arsenate were common wood preservatives in the last century and they worked well, killing off most things that came incontact with them.
They contain ammonia compounds, copper compounds and arsenic compounds some of which are very powerful poisons able to be absorbed by the skin or ingested by other means. Often these chemicals were contaminated with other powerful poisons too.
So ammonia may be one of the less dangerous chemicals that you have discovered so far on your beams.
Personally I'd leave them alone as any fire damage is the best preservative wood can be given.
Roman fence posts are usually completely decayed except for the deliberately charred post foot in the ground.
As it is you have no idea what you have been exposing yourselves to washing off the surface material.

 

[finn]

I'm sure you're right, but eeeughhh.....I'm now thinking some rather gloomy thoughts. Brushing down those beams was a very messy job, with lots of brown, gunky dust everywhere. We wore masks etc, but still.....

 

[biffvernon]

If there are heavy metals present I'd guess that they are not going to be dislodged by the limewash as they are non-volatile, so I wouldn't worry on that score. The ammonia produced will blow away and the reaction will stop in its own good time. Just do the limewashing on a breezy day with the windows and doors open.

 

[Lime]

If there are heavy metals present I'd guess that they are not going to be dislodged by the limewash as they are non-volatile, so I wouldn't worry on that score. The ammonia produced will blow away and the reaction will stop in its own good time. Just do the limewashing on a breezy day with the windows and doors open.

In all probability that is exactly what I would do if i wanted them to be limewashed (whitewashed).
The lime will be in excess and the reaction will eventually stop.
The reaction probably requires water too so when the wash dries out the reaction will stop.
However that could mean dampness may bring the smell back as our noses are very sensitive to ammonia.
You may benefit by lightly spraying the drying lime wash with water (keeping it slightly damp) until the reaction has ceased.

Obviously you need to wear a good mask that covers eyes and removes ammonia.

 

[finn]

Thanks for all the advice. We'll try again, well masked up and on a breezy day (no shortage of those recently) and see how we get on.