[GSBN] Straw Preservation in Clay _ Research Documents

[Anthony Dente]

Thanks a lot Andy.


On Thu, Oct 24, 2013 at 3:41 PM, Andy Horn
<andy at ecodesignarchitects.co.za>wrote:

>  ** **
>
> Dear Anthony****
>
> Afraid this comes as a rather delayed response, in regards your question
> about the long term preservation of straw in clay.****
>
> ** **
>
> Firstly I think is worth said that Bruce King’s book “Design of Straw Bale
> Buildings – The State of the Art” explains the science of it all rather
> perfectly. As for research documents I cannot help but I nonetheless
> thought a few tales were worth sharing ****
>
> ** **
>
> Firstly I know an artist, Peter Eastman who used to work in the
> antiquities department of the British Museum doing restoration work. He
> told me about how unbaked clay can preserve straw perfectly for thousands
> of years. He says that when restoring many old Egyptian sculptures, the
> easiest were the ones made of unbaked clay, which many of them were. He
> said that when working with them they would simply break down any shards of
> clay rewetting it to remould broken limbs and such back together again. He
> said that something that had always amazed him when busy with such works,
> was that he would find bits of sparkling yellow straw in the clay and that
> despite its 1000’s of years of age, nonetheless looked as fresh as if it
> had just been harvested. ****
>
> ** **
>
> The second was when I was travelling in a rather more humid Japan. In
> Kyoto,  I chanced across a demolition in progress of an old traditional
> Japanese “wattle and daub” house. The old construction, which could have
> been anything from 100 – 500+ years old consisted of a timber frame with
> infill panels of timber and bamboo lattice work with a cob infilling, which
> had a natural plaster on the one side and originally a timber cladding on
> the exterior. Upon examination I noticed how the straw (rice straw no
> doubt) in the cob used in the construction still looked and performed as
> new. The contractors were dampening the place down with water while they
> bashed the construction to the ground (sadly there are no heritage
> conservation laws in Japan that protect old buildings) so I took handfuls
> of the damp cob and worked it as if it were just newly made. I have
> attached some photos of  the straw clay bamboo construction and another
> revealing the construction – which hopefully  the server will allow..? If
> not then I will need to upload it onto media fire and send out a link.****
>
> ** **
>
> It was also interesting to note how vital moisture levels and air exchange
> is to the survival of straw rather than age per se. After taking the
> demolition photos, wanting to take a specimen with me, I snatched a sample
> of the old somewhat sodden sample of the clay and final plaster layer.
> Looking around I grabbed a handy piece of plastic and wrapping it up
> safely, stuffed it in my pack and then forgot about it. That is until
> finally a couple of weeks later when back home I unfurled the by now mouldy
> packet. To my dismay all the straw had moulded away to nothing. The samples
> were wet and because the wrapping did not breath, of course rot set in,
> ironic I thought after surviving perfectly for hundreds of years beforehand.
> ****
>
> ** **
>
> I have also observed in demolitions of old works how timber that is buried
> in clay, will be well preserved  especially in comparison with timber that
> has been laid in concrete, which will normally be rotted away.****
>
> ** **
>
> Best regards****
>
> Andy Horn****
>
> ** **
>
> Eco Design – Architects & Consultants****
>
> A. R. Horn BAS, B. Arch, Pr Arch, MIA ****
>
> 1st floor 79 Roeland Street, Cape Town, South Africa****
>
> +27 21 462 1614, www.ecodesignarchitects.co.za****
>
> ** **
>
> ** **
>
> *From:* GSBN-bounces at sustainablesources.com [mailto:
> GSBN-bounces at sustainablesources.com] *On Behalf Of *Anthony Dente
> *Sent:* 27 September 2013 10:45 PM
>
> *To:* Global Straw Building Network
> *Subject:* [GSBN] Straw Preservation in Clay _ Research Documents****
>
>  ** **
>
> Hello Everyone,****
>
> ** **
>
> I hope your Septembers are coming to a pleasant close.  I'm curious if any
> of you could point me in the direction of reports documenting the long term
> preservation of straw in clay plasters, cob walls, or similar.  Most
> importantly it's tensile characteristics.****
>
> ** **
>
> I have been aware for some time of the "common knowledge" that wicking
> qualities of clay's hydrophilic nature preserves such biodegradable
> materials and that this is the backbone of many clay building techniques.
>  I have even spoken with colleagues and friends who say they have chipped
> open buildings and felt these qualities themselves.  Though I am unable to
> locate studies/reports documenting significantly old structures (preferable
> in rainy climates) that have had boring tests done and confirm this.****
>
> ** **
>
> Thanks for any and all of your help,****
>
> Anthony****
>
> ** **
>
> Anthony Dente, PE, LEED AP****
>
> Kevin Donahue Structural Engineers****
>
> Berkeley, CA****
>
> 814.502.6001****
>
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