Making lime putty - Elementary questions

[biffvernon]

I am fully aware of the arguments for 1:3/1:4 mix............. but comparing them to historic mortars tells me that they can be too sandy and certainly not as forgiving as thos with a higher lime content. see summerlings work on lime/chalk aggregate/hair renders and plasters.

Ah yes, historic mortars. The lime you buy in a bag down the builders' merchant is 100% extremely fine particles so every bit of it counts as matrix not aggregate in the mortar. In historic mortars the crushing, grinding sieving process was all much more hit and miss so there would be a fair proprtion of lumps of lime. A mineral analysis of 1:3 calcite : quartz might not mean a mechanical analysis of 1:3 lime matrix : sand aggregate. With poorly ground and sieved lime you would need a higher proportion of lime.

 

[forky]

can anyone tell me why my bag of blue circle hydrated lime has written on the side: "as this is a non-hydraulic lime it is not to be used as a mortar." Obviously non-hydraulic is often recommended on this site as a mortar?

 

[MdB]

Elf an safety mate, elf an safety.

I raised this in the past and I think someone said that they had contacted blue circle about it. The answer that came back was something like that they were aware that it was suitable for mortar but as it wouldn't have anything like the strength of cement they didn't want builders to use it in the fashion as they might use it in the same way as cement. This could lead to a wall falling down and them getting sued. I've probably got this a bit wrong but it was something along those lines.

 

[forky]

hmm... seems a funny thing to write if you want people to buy it and use it as a mortar. But does say ok as mortar with addition of OPC. But I've read elsewhere this is definitely not the way forward.

Also says curing to make putty is 24 hours - what do you think to leaving it longer?

 

[MdB]

Also says curing to make putty is 24 hours - what do you think to leaving it longer?

I'm not sure what you mean by curing.

Making putty from hydrate basically means shoving it in a bucket with water. Mike Wye (who makes a living out of selling putty) says that putty matured for 3 months has better plasticity. I and others here have seen no evidence of this in actual use with just as good results using dry hydrate in the mix rather than making putty first. We believe that the idea of maturing putty might have come about when lime was supplied as lumps rather than as a fine powder. With lumps it could have taken longer for the water to soak through it. With the fine powder now supplied, the water will reach all parts almost instantly.

I do however, turn any spare hydrate I buy into putty as it will then keep indefinitely.

There are others here with far more experience than myself in using lime and might have a better insight.

 

[biffvernon]

Don't believe anything written by the cement industry, eg Blue Circle, on a bag of lime!

Bags of lime from Singleton Birch do not have such twaddle written on them.

 

[forky]

Don't believe anything written by the cement industry, eg Blue Circle, on a bag of lime!

Bags of lime from Singleton Birch do not have such twaddle written on them.

but you ignore what SB says on their bags too, am I right? you wouldn't use anything higher than NH1 for pointing except in very exposed situations. SB says NH1 only for interior or for exterior on very soft masonry. NH2 only for soft, sheltered masonry and NH3.5 is ok in most situations...

 

[biffvernon]

Hmmm.... that doesn't make much sense. Can't say I've seen a newish bag from SB.

 

[forky]

check out their instructions on their website

http://www.naturalhydrauliclime.com/index.php?display=what_we_sell&mode=products&cid=5

 

[forky]

also think their maths is off on pdf describing correct ratio of lime to sand

when adding water to sand to find correct ratio to fill all voids:
"volume of water added / volume of sand (and then times answer by 100) .... say eg answer is 30% then a 1 lime to 3 sand (by volume) will fill the voids....."

am i right in saying 30% is actually a ratio of 1 : 2.3?

 

[worms]

Air tight so as to not to dry out.

In my experience it would take a very long time to dry out. Once a calcite layer forms on the top of the fluid in the tub, evaporation is very slow. After two years, an open plastic container that I had in the garage was fine.

 

[biffvernon]

check out their instructions on their website
http://www.naturalhydrauliclime.com/index.php?display=what_we_sell&mode=products&cid=5

You mean:

Hydraulic Lincolnshire Lime
NHL 1
Natural hydraulic lime NHL 1 is a feebly hydraulic lime which is similar in strength and properties to the grey chalk limes, typically used for internal works and external pointing / rendering on very soft masonry. Slow setting
NHL 2
Natural hydraulic lime NHL 2 is typically used for internal works, external repointing / rendering and building on soft masonry in sheltered areas.
Conforms to EN459 as an NHL 2 product or feebly hydraulic.
NHL 3.5
Natural hydraulic lime NHL 3.5 is typically used for most repointing / rendering and building works on most masonry types
Conforms to EN459 as an NHL 3.5 product or moderately hydraulic.
NHL 5
Natural hydraulic lime NHL 5 is typically used for external works in exposed areas such as chimneys, copings or river and canal works and provides a faster, harder set. Conforms to EN459 as an NHL 5 product or eminently hydraulic.

That seems fair enough, if rather cautiously on the safe side (and from a company that is trying to increase sales of hydraulic limes). There's nothing there to disagree with, rather one could add that hydrated lime would also be suitable for the first two categories.

 

[forky]

ah, well I'll just pick NH2 or 3.5 or putty with pozzolan and I guess I'll be fine.