My BIL is helping someone with a home renovation which involves gutting a
100+ year old house. The original walls were plaster on lath which has been
removed. They would like to rebuild in such a way that the original
structural members are visible. (I have not seen it but I assume that it
must be post & beam construction). The structural members are some type of
confer. It is unknown what type of wood the lath was.

The problem is that the lath apparently left a dark brown stain where it
contacted the structural wood. The stain is not just superficial. it goes in
at least 1/8". Pressure washing and sandblasting were attempted with no
success.

What would cause this type of stain and might there be a chemical remedy?

Thanks,

Steve

Paint? Probably not what you wanted to hear. Semi transparent stain?
probably better than paint but will still leave a bit of evidence.

Bleaching probably wouldn't work but you could try. oxalic acid is often
used for wood bleaching.

Second google hit found this
http://alsnetbiz.com/homeimprovement/oxalic_acid.html

Good luck


"Stephen M" wrote in message
...
My BIL is helping someone with a home renovation which involves gutting a
100+ year old house. The original walls were plaster on lath which has
been
removed. They would like to rebuild in such a way that the original
structural members are visible. (I have not seen it but I assume that it
must be post & beam construction). The structural members are some type of
confer. It is unknown what type of wood the lath was.

The problem is that the lath apparently left a dark brown stain where it
contacted the structural wood. The stain is not just superficial. it goes
in
at least 1/8". Pressure washing and sandblasting were attempted with no
success.

What would cause this type of stain and might there be a chemical remedy?

Thanks,

Steve

Stephen M wrote:

My BIL is helping someone with a home renovation which involves gutting a
100+ year old house. ... I assume that it must be post & beam construction)...
The problem is that the lath apparently left a dark brown stain where it
contacted the structural wood. The stain is not just superficial. it goes in
at least 1/8". Pressure washing and sandblasting were attempted with no
success.

What would cause this type of stain and might there be a chemical remedy?

Cause is probably plaster reaction. As someone else noted, almost
surely it could be bleached out w/ oxalic acid, but my question would be
"Why would you want to do that?" Would seem the character of 100+ years
would be desirable...of course, after the previous adventures outlined
above, there won't be anything left so may as well give it a go...

On Tue, 14 Jun 2005 09:15:45 -0500, Duane Bozarth
wrote:

Would seem the character of 100+ years would be desirable

The "character" of 100+ years often looks quite different to what 100+
years looks like.

Certainly in interior design.