Powder hydrate lime

[rebeccac]

Having had huge problems finding NHL 3.5 lime for sale in our part of Italy I've been using an Italian hydrated lime (at 2.68 euros a 25 kg sack) to make lime putty.I leave it for 3 - 10 months to mature.Its called 'flowers of lime' and does seem to be a slightly different type top the uk hydrated lime I've used.

It seems to be a good mix and I've got trial patches of plaster and external pointing that are years old and still good.

I've read in books that this type of lime isn't as good as the more expensive NHL lime but apart from it being a bit softer - which as we have a soft sandstone and old bricks is desirable - I cannot really see the problem? And it costs just around 1 euro to make tub of limeputty.Anyone had problems using this lime?

 

[biffvernon]

Sounds good. Wish it were that price here.

 

[masochists-r-us]

Can't help myself, but I remember an old thread entitled 'Italian Lime' where user ljn claimed to have lived there for 25 years so it might be worth getting in touch with him or her.
Good luck

 

[rebeccac]

Yes why is lime so much dearer here? We can buy bags of hydraulic lime at that price too and a product that is sublime to use called 'bio calce intonaco. Its lime , sand , marble dust and a pozzolan and something else ( not cement) lovely to use and only 6.44 a sack.

Bio Calce have a website! http://division.biocalce.it/

 

[Flyfisher]

Yes why is lime so much dearer here?

Why is almost everything more expensive here? :evil:

 

[Stephen]

There is much debate over the use of bagged hydrated lime.

The purists would argue that it should never be used and others would say that it is but one of a range of lime products that might be appropriate for certain situations. I personally fall into the latter category.

In many situations it would be better to use lime putty ('fat lime'), but it is not always essential and may depend on location in building, application, time of year, etc, etc,. For example a limeputty mortar may not be suitable for work to brickwork at low level and to chimneys, whereas a nautrally hydraulic lime would often be better.

Some would argue (and I would generally agree) that instead of NHL use lime putty with a pozzolan but this is not always practical and if money is tight it may be more economical to simply go for NHL.

With some buildings (such as non listed Victorian and Edwardian buildings) using a hyrated lime would be better than using cement. As most owners and builders working on Victorian and Edwardian buildings either don't care or are only bothered about cost it is surely better that they use Hydrated lime than cement (they would not even consider lime putty or NHL on the basis of cost).

The above is an outline of the general discussion over the use of hydrated lime.


I think we have to be careful about considering what happens in Italy and assuming we can do the same here. There is one major difference - the climate! I think we can learn things fromabroad, but we often have to be careful if the example is from a country with a different climate.

Hope this helps.
Stephen

 

[rebeccac]

Stephen your post has slightly confused me as it is lime putty I'm using rather than powder.Is there much difference in the matured putty I make from hydrated lime and the putty made from slaking lime ?

We do have very hot temperatures in the summer which effects the set of lime and prevents its use for at least 2 months but in April I had 10 days of rain and at the end of June it rained so much that I had to mop up a few leaks! We also get cold wet winters so many old properties have the same damp problems as we get in the UK.

I found out about using hydrated lime powder to make putty from an American book on Natural Plasters. And recently I read a very informative article that points out just how many varities of plaster have been made and used over the centuries all giving good and lasting results from all types of mixes.

 

[MdB]

Not an expert but I have looked into this.

Chemically there is no difference between going slaked lime + lots of water -> lime putty or slaked lime + right amount of water -> hydrated lime + more water -> lime putty.

The leaving lime putty to mature thing may have been valid historically when the lime wasn't very well crushed and had lumps in it. The hydrated lime now available is very finely ground so I don't think converting to putty and then leaving makes a lot of difference compared with using it directly into a mix. I could be wrong on this.

I asked Mike Wye (http://www.mikewye.co.uk/) this question on one of his training courses and his response was that matured lime putty has better plasticity. I've not noticed a difference myself.

The only big issue with using hydrated lime is carbonisation within the bag. I've had this happen to one half used bag I had lying around for a year or so. You want to source it from a builders merchant that has a good turn over of stock and doesn't have it hanging around for ages.

When I have a job needing lime, I buy a new bag of hydrate and mix mortar using the hydrate directly, I don't make putty first. If have any hydrate left over though, I turn it into putty so that it will keep and use this next time.

 

[biffvernon]

I agree.

 

[christianb]

In my opinion, bagged hydrated lime left to fatten up for a few days is as good as any other lime putty - and a great deal cheaper. I've used it successfully on numerous occasions and have managed to bring down the materials cost for people to the same as they would have paid to do the wrong thing (i.e. they had considered using bagged gypsum on the historic fabric of a building).

I've also mixed it with NHL2 for plastering and find it improves the workability immensely.


Absolutely nothing wrong with the stuff whatsoever. It is, after all, lime which is part-slaked and you just finish the job off.

C.