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Subject: Bora-Care


From: J. Bryan Blundell <jbb>
Date: Tuesday, May 21, 2002
Frank Briscoe <fbriscoe [at] wsbellows__com> writes

>... I would be grateful to know from
>members of the list what their experiences have been in matching
>finishes on wood materials treated with Bora-Care, and if they have
>achieved lasting installations using Bora-Care on cypress material
>other than the first-growth specified for this project.

Based on 12 years experience using BoraCare and other Boron based
wood preservative products, I am not aware of  problems with
BoraCare applications on cypress material.  There are only two
problems that I have been aware of with applying finishes over
BoraCare or Boron treated wood. One is that salt sensitive epoxies
will not adhere to Boron treated wood. The other is that shellac
based finishes can be softened if applied over BoraCare too soon due
to the glycols in the formulation. Since the active ingredient is a
Boron salt, over application can leave a residue on the surface that
will interfere with most coatings. It appears that the raw Boron
salt based products tend to leave more of a residue on the wood

The risk of leaching of Boron is a concern for ground contact
conditions were there is a path of migration. The Boron can migrate
into the soil that is in contact with the treated wood.  Thin wood
elements, such as wood roof shingles, can simulate a ground contact
condition. Thin wood elements can become saturated during long
periods of rain and the water running across the surface can provide
a path of migration. This "Path of Migration" typically does not
occur with thicker pieces of wood that are not in these "Path of
Migration" conditions. The wood is not a sponge that is squeezed to
force moisture out to dry it when it gets wet. The wood gets damp
and the Boron becomes more mobile. The wood gets drier, the Boron
becomes less mobile. With the glycol formulation, the Boron is
soluble at a lower wood moisture content than the raw Boron salts.
This allows the Boron to continue to migrate into the wood at
moisture contents that would have stopped the migration of the raw
Boron salt application. In typical applications, the raw Boron salt
provides a shell protection ( the label provides guidelines based on
square foot of surface) while the BoraCare is intended for a
penetrating application ( the label provides guidelines bases on
board feet of material).

J. Bryan Blundell
Technical Support
PRG, Inc.

                  Conservation DistList Instance 15:79
                  Distributed: Wednesday, May 22, 2002
                       Message Id: cdl-15-79-002
Received on Tuesday, 21 May, 2002

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