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Kiko Denzer on Art

[Cob] crack in plaster

Dulane silkworm at
Tue Sep 16 17:29:24 CDT 2008

I found that when I got some crack in a lime/clay wash, that when I painted
over it later with just a wet brush (maybe a wet sponge or rag?), the cracks
went away. I'd probably advise doing this out of direct sun and heat. It
can't hurt to experiment.

-----Original Message-----
From: coblist-bounces at [mailto:coblist-bounces at] On
Behalf Of Bob Smolen
Sent: Monday, September 15, 2008 11:21 PM
To: coblist at
Subject: [Cob] crack in plaster

I have a small section of cob wall that I have covered with 2 layers of a
coating of 3 parts sand , 1 part clay, and 1 part lime. I spread this on in
a fairly dry mix and let dry for a week during a hot , dry spell 80+ temps.
I sprinkled the wall with water each day but the plaster developed many thin
cracks (spider web like). These cracks formed almost as soon as the wall
dryed,in a day or so. Nothing fell off and the coatings seem to be adhering
well.  Sunday I plastered with a mix of 3 parts sand to 1 part lime. The
coating was not real thick, say 1/8 in. in most places. This ccoating has
developed a few spider cracks. Should I be concerned or is this normal? Will
an all lime plaster be a good final coat?
The sand I have is fairly coarse but I have screened it down to 1/8 size. 
I forgot to mention that I had straw/dry grass mixed in the first coats but
nothing in the last 3/1 mix.
Thanks for your comments,
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