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Date: | Tue, 12 May 2009 12:48:19 +1000 |
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Randy wrote
> A point not always made clear in this discussion is whether the hot-dipped
> or copper-treated are then painted. Old research from Forest Products
> Laboratory demonstrated that painted pine wood lasts many years longer if
> treated with a water-repellent preservative (WRP) prior to painting.
> Simple
> paint over raw pine has a very short life, especially over the end grain.
> Rot generally starts there.
If you can keep the moisture out of timber then it will not decay (rot).
Paint usually has the problem with bee boxes in that the paint is broken by
use of a hive tool and water can get in. If you can keep the moisture
content of the timber below 20% then you will not get decay. This is why
some climates are not conducive to decaying timber as the equilibrium
moisture content (EMC) of the air is below 20%. This is not to be confused
with relative humidity. You can have high temperatures and high humidity
but a low EMC. There are charts out to do the calculations.
Water repellents are just that and by keeping the water out, stop decay.
However I think it is in the Kalins and Detroy paper where they used tri
butyl tin oxide (TBTO), which is a common water repellent, and they got
residues in the honey. So I would be wary of any other water repellents.
I paint the inside of my boxes. These have been treated with copper
naphthenate. I do this to reduce the possibility of any copper residue in
the honey. Kalins and Detroy used a copper naphthenate solution which is
about 10 times stronger than I use. They obtained elevated levels of copper
in the honey and the inside of their boxes were not treated.
Many years ago there was a survey done of honey for residues in Australia by
Graham Kleinschmidt. He did not find any elevated levels of copper in honey
from hives that had been treated with copper naphthenate and painted inside.
Not sure if there were boxes that had not been painted on the inside.
Trevor Weatherhead
AUSTRALIA
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