Civil Engineering Reference
In-Depth Information
Recipe for lye made from soda and potash
The soda solution is made by boiling 5 litres of water with 250 g of soda powder. The liq-
uid is applied when still warm. Potash solution is either based on pure potassium carbon-
ate or on wood ashes, which contain about 96 per cent potassium carbonate. A potash
solution is made up by boiling up 2.5 litres of pine ash with 5 litres of water and letting it
simmer for 15 minutes. The solution is sieved and applied while still warm.
Bor salts from borax and boracid
These impregnating substances combine effectiveness against vermin with rela-
tive harmlessness to humans. The emission period from an impregnated surface
is as short as 10 hours, so the interior of a building will be risk-free after a couple
of days.
In Germany borax is the only one of the more effective poisons used indoors.
It is also used to impregnate cellulose insulating materials where it also acts as a
fire retardant. It is, however, quite easily washed out of materials. Borax is
bought as powder, and usually used as a 5-10 per cent solution in warm water
applied in two coats. Very dry timber is moistened first so that the borax will
penetrate better.
Green vitriol
Green vitriol is a relatively harmless impregnating substance based on ferric
sulphate. In liquid form it can irritate the skin and is slightly damaging to
organisms living in water. A good impregnating solution consists of
10-13 g/litre of water, with a little alum added as a fix. Green vitriol is also a
fire retardant and gives timber a shiny silver surface. It is often called acid
treatment. Such a treatment can last up to 15 years but will in time be washed
out of the timber.
References
G
ODAL
J B,
Tre til tekking og kledning
,
Landbruksforlaget, Oslo 1994
G
USTAFSSON
H,
Kemisk emission från byggnadsma-
terial
, Statens Provningsanstalt, Borås 1990
J
OHANNSSON
G,
Kvalitetskrav på byggnadsvirke
,
Byggforskningsrådet Rapport 105, Stockholm
1990
N
ORGES
B
YGGFORSKNINGSINSTITUTT
,
Luftede kled-
ninger og fuger. Påkjenninger, prinsipper og
virkemåter
, Byggdetaljer A 542.003, Oslo 1989
Section 3: Further reading
A
DDLESON
L,
Materials for building
, London 1976
A
SHURST
J
et al
,
Stone in building. Its use and poten-
tial today
, London 1977
B
ECKLY
A,
Handbook of painting and decorating
products
, London 1983
B
ERG
A,
Skifertekking og skiferkledning
, Forening til
Norske Fortidsminnesmerkes Bevaring, Års-
beretning, Oslo 1945
B
ILLGREN
G
et al
,
Träfönsterets beständighet
,
Byggforskningsrådet, Stockholm 1977
