Limewash experts - help please

[biffvernon]

is there any way to tell if hydrate is too old to use? Secondly, can I assume that once I have used the limewash made from hydrate of uncertain age, that as long as the limewash turns bright white after 24 hours that carbonation has occurred and that it must have been OK?

No. (Well, not easily at home.)
No. It turns bright white when it dries. The carbonation reaction is a much slower process. When using whitewash (chalk dust = calcium carbonate) it still turns bright white without any carbonation.
An old bag of hydrate will still be useful for mortar. Even if, say, 50% of the calcium hydroxide has carbonated, you're still left with 50% that hasn't. Just use a richer mixture and assume part of you bag is aggregate fines.
Your Leylandii will grow well with no need for liming.

 

[Moreteyne]

If you mix your lime-wash like cream it will not carbonate correctly and will eventually peel and flake. Putty is by far the best for lime-wash although Hydrate can be used. I tested a cream lime-wash to milk lime-wash on our windmill. Results - fours years hence, milk lime-wash stuck fine and is still in good condition. Cream like consistency has all but flaked away and left lots of patches all over the exterior. Planning on re coating spring this year, all being well.

I think the issue with thick lime-wash is that the top layer will carbonate but does not allow the underneath portion to carbonate in time so it remains un cured. Best to apply thin coats . let it go off then apply new coats.

 

[Pford75]

Never used goggles as I wear glasses anyway and these seem to keep minor splashes away. I do have a respirator that I use for a variety of jobs (bodywork on cars, sanding etc.) It's a fairly decent one (£10 from B&Q or thereabouts) and has removeable cartridges that you replace over time (one is for dust and small particles and there is another one for paint/vapours etc.) Felt expensive at the time, but one of the best investments I've made...decent straps to keep it on your head and doesn't seem to mist my glasses.

For the reasons you mention, I tend to use distemper on the ceiling...it seems to offer a slightly better consistency, although short sleeves are still recommended. I haven't tried it myself, but a plasterer I know claims that he uses a sprayer to apply limewash to ceilings and then just finishes it with a brush. Either way, it's much easier to clean up afterwards than if you had used emulsion.

 

[worms]

Your Leylandii will grow well with no need for liming.

The Leylandii are at least 35 years old, so growing well is not the problem! The lime is to tone down the acidity in the shady border below it!