It's not unreasonable, it's what any sensible person would do in order to make an informed decision.

Thing is, in my experience, the guys who run these companies tend (certainly in the case of Lime Green) to be enthusiasts who have not only gotten into the business by accident (unable to source what they were looking for they decided to do something about it), but lecture on the subject on conservation courses at local colleges.

Without exception, every such specialised operation I've ever had dealings with has been characterised by an open, friendly approach, in fact the absence of hard-sell has been singularly evident. Womersleys is an object-lesson to all commercial operations that claim to have customer service at the heart of their business.

And who said you were being unreasonable?

Ok, so, I'm going to try making some putty from bagged hydrated lime as I'm curious to see what it's like to work with.

Better as it gets older.

Can't find any instructions on what exactly to do though. How much water? Do I mix it up to a putty consistency, and then cover that with water?

Yes

Won't it just turn into a big milky soup?

No

Do I need a tub with an airtight seal?

No. The water is that.

At least a week (tutting guaranteed)
Preferably a month (or more).

It will get thicker the longer you leave it to the point where if you use it too quickly it will be like soup and you'll struggle to get the mix dry enough. Over 6 months and it sufficiently dense that it takes more mixing.

Given you want to keep it 'fresh' you could do the whole bag so when you convert to lime you'll have some extra mature stock ready to go.

OK. Thanks for the tips.

Meanwhile, my reading of the Smeaton report brings up the following observations:

They exposed various mortar samples to the elements and freeze/thaw cycles, and rated the level of deterioration from A(not much deterioration) to E(badly deteriorated). Selected results after 5 years:

3 sand : 1 quicklime putty ----------------------------------------------- E
3 sand : 1 putty from hydrated lime ------------------------------------ D/E
3 sand : 1 quicklime putty : 1 brick dust ------------------------------- A/B
3 sand : 1 quicklime putty : 0.1 OPC(Ordinary portland cement) --- E
3 sand : 1 quicklime putty : 0.5 OPC ----------------------------------- B
3 sand : 1 hydrated lime : 0.1 OPC ------------------------------------- D
3 sand : 1 hydrated lime : 0.25 OPC ------------------------------------ B
3 sand : 1 hydrated lime : 0.5 OPC ------------------------------------- A/B
3 sand : 1 Hydrated Hydraulic lime (buff) ----------------------------- A/B
3 sand : 1 Hydrated Hydraulic lime (white) --------------------------- D

This suggests to me that a sand/non-hydraulic putty mix should only be considered for anything exposed if some brick dust is added to the mix.



All this suggests that a 1:2:9 mix shouldn't be considered too risky really. It seems that its hygroscopicity and vapour permeability is not massively worse than a putty mix, and that in terms of durability it will perform as well as a putty mix including a brick dust pozzolan, and significantly *better* than a putty mix with no pozzolan.

The only thing that may still be an issue is of course the hardness of the mortar relative to the bricks. Would like to see this quantified too.

I was kind of expecting people to tell me I'd misinterpreted it all by now...

Posted By: jms452Well I wouldn't agree with your statement 'This suggests to me that a sand/non-hydraulic putty mix should only be considered for anything exposed if some brick dust is added to the mix.'

On account of being dubious about the reliability of the smeaton experiment results?

I'd certainly agree that caution should be taken with regard to those results, unless they have been replicated elsewhere.

The report I saw was "phase 1" and I gather there were subsequent phases but I have been unable to track those down.

There does seem to be a lack of real experimental data on this whole question, at least in the context of the degree of certainty with which many seem to state their opinions/advice.

And for latecomers...

http://www.lime.org.uk/case-studies/

Mike Wye's factsheet (''Please note that great care should be taken not to be applied too late in the year or too soon in spring or else frost damage may occur. It is important to prevent frost crystals forming within the mortar soon after application. The ultimate hardening process takes up to a month for each millimetre of thickness. Therefore it may take 20 months before mortar has carbonated to a depth of 20mm.'') may provide the answer, but I didn't have this sort of problem rendering with NHL 3.5 3 or 4 years ago.

Posted By: Mike GeorgeHi Lineweight. We had a big discussion here a whileback on whether or not OPC should be used [at all] I'm pretty sure we got into mix proportions with hydrated lime a fair bit from page 2 on. Anyway it may helphttp://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1554&page=2" rel="nofollow" >http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1554&page=2

Thanks - have had a read through but unfortunately am no further forward in terms of finding something solid on which to base my opinion! (Although, some interesting discussion on the embodied energy issue)

I'm a bit disappointed that no-one's really come back on the figures I posted a bit earlier.

I can see and understand the issues relating to vapour permeability/hygroscopicity, and that these are important when dealing with old brickwork and traditional construction with timbers embedded in the wall and so on.

Clearly, lime has an advantage here, one that is quite well proven and shouldn't be ignored.

So you might say, well, lime mortar is known to work, and has been used for hundreds of years, so why not just cut out OPC altogether. My main objections to this are:

1) cost. The fact is that it's more expensive. This can't be ignored. Ok, so you can make your own lime putty from hydrated lime (and I'm trying this at the moment out of curiosity) but this is time consuming and also there has been some doubt expressed about the quality of putty made in this way - doubts about how fresh the bagged lime is for example.

2) The durability argument. So, loads of old buildings have survived hundreds of years with lime mortar. Fair enough, but the ones that have survived are somewhat self-selected. So I'd say it's more accurate to say that *some* lime mortars have proven to be very durable. The thing is though that the more I read into it, there seem to be loads of variations and the additives such as brick dust or whatever else seem to be significant. That Smeaton project seems to raise some concerns about the durability of lime mortar without pozzolan. Also, I read in quite a few places that Victorian builders would sometimes gauge their mortar with OPC. Lots of Victorian buildings are still standing...how many have OPC content in the mortar and how many don't? There's just a bit too much vagueness for my liking.

3) Speed of work. Like cost, this can't be ignored. Time is money, etc. Arguably not so significant for repointing, perhaps, but even then, there are considerations about frost damage. 1 month per mm of mortar was mentioned just above... if that's true then that cuts out a fair chunk of the year where you can't use a pure lime mix without worry.

4) Ease of use: it's been suggested that a putty-based mix is nicer to work with. Hence, I'm going to try it. Will report back in due course.

So, what about the alternatives. The main one seems to be the quite widely used 1:1:6 mix, for example. So, I'bve tried to look at why this *shouldn't* be used. Main arguments seem to be as follow:

1) The permeability/hygroscopicity issue. My figures above seem to suggest that this is definitely a reason to avoid a pure OPC mix, but a 1:1:6 remains pretty permeable.

2) Durability. Where's the evidence that durability is a concern? Is there any evidence of 1:1:6 mix mortars failing prematurely? I can't find any. The Smeaton project seemed to suggest that such a mix performed pretty well, not significantly worse than the best of the lime mixes (and significantly better than many of them).

3) Excessive strength. As in, not allowing movement resulting in the masonry units themselves cracking etc. This is the main one I don't feel I've got a good answer for. Haven't found any figures or anything definitive quantifying this. If anyone can help I'd be interested to hear. Seems like no-one round here is interested in actual solid figures though [/deliberate provocation].


I do have a feeingl that many have a kind of aesthetic attachment to the use of lime, and will therefore bias their reading of the evidence to support this. As for the various lime suppliers... I don't doubt their good intentions and so on. But just because they are nice people and good businesses etc - doesn't mean that everything they say or believe is strictly true, certainly not unbiased anyway.

Most homeopaths are well intentioned too, but... well, there's another provocation for you...

Have just come across quite a good overview of matters lime-related here:

http://www.icevirtuallibrary.com/content/article/10.1680/coma.900053

[edited to correct link]

Posted By: nikhowardA bit late in the day, but I was in a similar position years ago, spent ages researching, trial mixes, etc but settled on 1:1:6.

Can you remember your reasons for choosing this over a lime-only mix?

Just rediscovered the thread ...

Posted By: lineweighthttp://www.icevirtuallibrary.com/docserver/fulltext/coma164-013.pdf?expires=1355271585&id=id&accname=guest&checksum=7B7AE9C0BA67E68F44DA3BF2C8D88B73

"The page you requested is not available"

Any other details that will let me find the information?

Sorry...haven't logged in for a while and only just saw this.

Not sure how I ended up with the link I posted...here's the correct one:

http://www.icevirtuallibrary.com/content/article/10.1680/coma.900053

Just rereading this thread yet again and noticed

Posted By: lineweightit's been suggested that a putty-based mix is nicer to work with. Hence, I'm going to try it. Will report back in due course.

Did you ever get any reults with your home-made putty?