Best recipe for limewashing charred ceiling beams/joists

[finn]

Hi,

I know that there have been some posts on this subject in the past, but I'm still a bit confused as to the best recipe/method for limewashing charred ceiling beams in an old farmhouse that we're restoring. The beams/ joists were very blackened- we think that there may have been a fire in the house long ago. The beams/joists are structurally sound, but were covered with a layer of charcoal-like dust, which (with much effort) we've brushed off. They now look quite good, if you like very dark wood beams.We don't particularly. We want to limewash them, but are worried about the charcoal/soot staining through the limewash. We're also keen to make sure that the limewash adheres. We''ve read various different recipes/advice on the net, but are now a bit bewildered by so much differing information. We were thinking lime putty mixed with water and linseed oil, but not absolutely sure of exact ratios/quantities. Any final words of advice...anyone.......?

 

[middi]

I would not mix anything with the limewash, just clean the beams with sponge, clean water and plenty of old cloths to wipe them as clean as you can then apply the whitewash (limewash)

The reason I am suggesting this approach is because this simple application is totally reversible in the event that you are unhappy with the result ( due to the state of the beams), You can easily wash it off again if you need to.

If you add linseed oil to your limewash mix or use other bonding agents it will be much harder to remove if you are still unhappy with it.

Old beams are usually pitted, split and in some cases full of old surface woodworm holes, once "sticky" surface paint has entered this crevices it is a nightmare to clean them again.

You can recoat limewash as many times as you like and wash it all off just as easy.

 

[chuckey]

I was thinking does the smoke/charcoal areas wet out. i.e. if you wet it, does the water roll of or soakk in? Soot seems to be greasy, water put on it falls of. If the water does not soak in, limewash without linseed oil will also run of? Also if the wood is deeply cracked. lime wash getting in these will prove to be inretrievable.
I would try to clean the wood up 100%, have you tried a fine wire brush, often available at cheapo tool stalls in markets, about 8" long curved end, plastic handle, brassy looking wire( don't be fooled) ~£2. Does not damage wood easily.
Frank

 

[finn]

Hi again,

Thanks for your posts- we did use a wire brush as suggested to get rid of the soot, and will definitely wash them down as suggested (perhaps using sugar soap?) But I suppose that what I really need is the best or most reliable recipe for making limewash. Some people say hydrated lime, some say lime putty etc., some even say that mildly hydraulic is okay. We want to limewash to keep the beams breathable, but at the same time we don't want any tarry stains coming through (which is why the linseed oil seemed to make sense). We just want to get the mix right as regards quantities and ratios.

 

[Ian Bond]

I used a rich limewash to cover my dressed softwood tie-beam.

Fat lime putty (non hydraulic) mixed in a 2:3 ratio with water, and nothing else added. It took 3 coats before it started to look anything like a solid colour, and the timber was in a clean state.

It's not a perfectly uniform finish either, with one or two patchy areas, but that's part of the charm.

I'm not at all confident that I could achieve as good a finish on charred oak beams, but you could always have a go on a small area. If it doesn't work out you can always wash it off and emulsion it. Perhaps an 'eco' emulsion?

It required patience - I dampened the wood lightly before limewashing, and always left at least 2 days between coats. There are no shortcuts or guarantees of success.

btw - steel wool or ferrous iron brushes aren't a good idea for scrubbing woodwork down, as little bits can get left behind in the wood and cause rust stains that show through the work. I think that's why Frank mentioned the brassy looking wire.

Ian

 

[Ian Bond]

... I'd imagine anyone reading this who's spent several back-breaking & soul destroying weeks/months stripping emulsion off their beams will be cursing me for that comment I made about emulsion!

:lol:

 

[finn]

Thanks for the info- funnily enough, I was just looking at your photos of your limewashed room earlier today. It looked great. We'll go with the lime putty, 2:3 mix as suggested, and no linseed oil and see how we get on.
P.S- Did you sieve your mix, or is it not strictly necessary?

 

[Ian Bond]

Hi

Thanks - it looks better in natural daylight, or better still by candle light!!!

I did sieve the limewash. However, I just mixed the stuff using a piece of oak lath and arm power. The results are not as smooth as I'd hoped up close - a sandy finish.

It won't be too difficult to fix next time I decorate, at least not as hard as removing all the modern emulsion was. A quick wash down to get the bits off, then I'll hopefully be able to limewash again but this time master the smoothness.

I've "cheated' and bought a mixer attachment for my power drill so I can mix the limewash more thoroughly, and I'll be more careful with the sieving.

Still, it's not bad for a first go, and it was (almost) fun.

Ian

 

[Ian Bond]

Here's the tie-beam after the limewash has thoroughly dried:

The sides of the beam has been enclosed with moulded softwood boards, and the underside was lath and plastered to make them look more attractive I suppose. The structural tie-beam is visible from the attic room, and it is rather rough and ready. Certainly not a susbstantial and nicely moulded hardwood beam.

For best results don't put each coat on too thickly to try and get quicker coverage, or it will tend to powder and flake off. Thin coats and allow plenty of time between them.

As I mentioned, I made the limewash into rather a thick mix for the ceiling. The colourwash on the walls was more dilute, around 1 part lime putty to 2 parts water, plus pigment in solution.

Don't panic when the the limewash looks transparent as it goes on - it will dry white (or to a lighter shade of the wet colour). And it'll go transparent again when you spray it up with water prior to recoating. But the white/colour does build up, just takes time.

It's great when you go back into the room several hours later and see the 'magic' transformation that's taken place - who want's the boring predictability of emulsion?

Oh, alright the other 99.9999% (sensible) proportion of the population, I suppose