Cob: Plaster finish question

Wed Aug 27 00:10:40 CDT 2003

Ed,

Raduazo at aol.com wrote:

> At the price drywall joint compound would be cheaper, and you get a 
> free bucket with every purchase, and it might be more environmentally 
> friendly too.

I am not an expert on drywall mud, but think it is basically a chalk 
like mortar.  I've never applied it to an earthen wall and would under 
no circumstances use it for an exterior wall plaster.

> My question is: Has anyone ever used corral or ground up sea shells 
> with lime to make a finish plaster?

I've seen seashells embedded in a lime mortar for decoration.   I know 
that lime has been produced from burning coral and seashells.   I've 
visited a 1894 built, and recently replastered,  small country hospital 
that used a lime + sea sand + fern glue based lime finish rendering over 
an earthen wall.   Apparently it took a long time to fine the same kind 
of beach sand that was originally used on the wall.

Seashells should be no problem.

> How does it work? I would rather use a white silicon sand, and there 
> are a couple other places near Washington that have yet to try. 

This would work to.

>   Another alternative is to use any sand and then apply a pure lime 
> white wash, but I remember white washes of my youth that came off on 
> your hands and clothing every time you touche them, and I don't want 
> that either. 

You can apply a thin, straight lime mortar with light colored fibre and 
no sand in it for a finish color.  This method can give a shiny look if 
you rub it enough, but I think its time consuming.

>
>  Can anyone tell me what works the best on cob?

I'm familiar mostly with a three coat method for very professional 
finishes.   The first being the hard earth core, the next coat has a 
little more sand in it and finally the lime rendering.   Some places 
with a sand with lime before the pure lime with fibre finish is applied.

>
> Ed

Darel
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Ed,<br>
<br>
<a class="moz-txt-link-abbreviated" href="mailto:Raduazo at aol.com">Raduazo at aol.com</a> wrote:<br>
<blockquote type="cite" cite="mid1a1.19531a04.2c7a82f3 at aol.com"><font
 face="arial,helvetica"><font size="2" family="SANSSERIF" face="Arial"
 lang="0">At the price drywall joint compound would be cheaper, and you
get a free bucket with every purchase, and it might be more
environmentally friendly too.</font></font></blockquote>
I am not an expert on drywall mud, but think it is basically a chalk
like mortar.  I've never applied it to an earthen wall and would under
no circumstances use it for an exterior wall plaster.<br>
<blockquote type="cite" cite="mid1a1.19531a04.2c7a82f3 at aol.com"><font
 face="arial,helvetica"><font size="2" family="SANSSERIF" face="Arial"
 lang="0">My question is: Has anyone ever used corral or ground up sea
shells with lime to make a finish plaster?</font></font></blockquote>
I've seen seashells embedded in a lime mortar for decoration.   I know
that lime has been produced from burning coral and seashells.   I've
visited a 1894 built, and recently replastered,  small country hospital
that used a lime + sea sand + fern glue based lime finish rendering
over an earthen wall.   Apparently it took a long time to fine the same
kind of beach sand that was originally used on the wall.<br>
<br>
Seashells should be no problem.<br>
<blockquote type="cite" cite="mid1a1.19531a04.2c7a82f3 at aol.com"><font
 face="arial,helvetica"><font size="2" family="SANSSERIF" face="Arial"
 lang="0">How does it work? I would rather use a white silicon sand,
and there are a couple other places near Washington that have yet to
try. </font></font></blockquote>
This would work to.<br>
<blockquote type="cite" cite="mid1a1.19531a04.2c7a82f3 at aol.com"><font
 face="arial,helvetica"><font size="2" family="SANSSERIF" face="Arial"
 lang="0">  Another alternative is to use any sand and then apply a
pure lime white wash, but I remember white washes of my youth that came
off on your hands and clothing every time you touche them, and I don't
want that either. </font></font></blockquote>
You can apply a thin, straight lime mortar with light colored fibre and
no sand in it for a finish color.  This method can give a shiny look if
you rub it enough, but I think its time consuming.<br>
<blockquote type="cite" cite="mid1a1.19531a04.2c7a82f3 at aol.com"><font
 face="arial,helvetica"><font size="2" family="SANSSERIF" face="Arial"
 lang="0"><br>
 Can anyone tell me what works the best on cob?</font></font></blockquote>
I'm familiar mostly with a three coat method for very professional
finishes.   The first being the hard earth core, the next coat has a
little more sand in it and finally the lime rendering.   Some places
with a sand with lime before the pure lime with fibre finish is applied.<br>
<blockquote type="cite" cite="mid1a1.19531a04.2c7a82f3 at aol.com"><font
 face="arial,helvetica"><font size="2" family="SANSSERIF" face="Arial"
 lang="0"><br>
Ed</font></font></blockquote>
Darel<br>
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