Evening star., 1936-05-09
PAINT DESCRIBED
AS SSELF-CLEAN|NG
Pigments Developed Which
Collect Less Dirt, Chem
lists Told.

The painted white house, in dam
ger of extinction because 1t solled so
easily, is now saved to American land
scapes by the chemical development
of pigments which collect less dirt
than the old style house paints, DR..
C. F. Rassweiler of prominent man.
ufacturing firm, reports to the Amer
lean Chemical Society.
THE problem of dirt collection be-
comes increasingly important with the
spread of industrial areas" he de-
clares In recent years it has seemed
that the attractive white house Is
doomed, for even in suburban areas a
white house becomes so dirty after the
first Winter Of exposure as to be eX-
tremely unsightly. The most interest
ing development in decreasing the dirt
collecting tendency has been the use
of titanium pigment in white house
paints.
While discoloration has sometimes
been due to actual chemical reaction
of the pigment and the sulphur gases
in the atmosphere, the most important
cause of discoloration has been SIM
pie dirt collection on the surface OF
the paint. Good house paints have
always weathered away by slow sur
face erosion, but this erosion has been
coarse and irregular with the result
that the dirt was carried away in spots
and left sticking in others, and the
house thus assumed spotty, blotchy
condition.
Nature of Erosion Changed.
"By the judicious introduction of
titanium pigments, it is possible to
change the nature of this surface
erosion so that the chalking is very
fine and uniform, and not only do the
loose pigment particles wash away
with the rain. taking the dirt with
them, but also the pigment particles,
appear whittier when loose on the sur
face than when embedded in the film
"Chalking or self-cleaning whites,
when first introduced good may years
ago, developed bad reputation be-
cause the formulas represented an i'm
proper balance and the chalking was
ly and had poor ultimate life. This
has now been overcome by a more
judicious balancing of ingredients, and
a considerable degree of self-cleaning
can now be combined with an actual
slight increase in ultimate durability" :"
Paint blistering and peeling have in
creased under new construction meth
ods and will increase still further with
the wider adoption of air condition
ing in homes, according to DR.. RaSs-
weller.
Fault in Old Method.
Under old construction methods,
he says, there was relatively free cir
culation of air from the basement up
behind the siding and out through the
shingles Of the roof, with the result
that little moisture peeling of paint
took place. To avoid fire hazards,
modern building construction has re-
tarded this free circulation Of air be-
hind the siding Of house and as a
result moisture peeling has definitely
increased.
"Of course, moisture peeling can be
produced by loose joints, but it must
be recognized that even good construc-
ton may accentuate moisture peeling
by limiting the circulation of air. 1t
has been demonstrated that in heated
dwellings, moisture tends to travel
from the warm interior to the cold
clapboard surface.
las the moisture content of the air
inside Of frame houses is raised by the
more widespread use Of air-condition-
ing, we may expect serious increase
in general paint blistering and peeling,
"At present the prevalence of mois-
ture peeling is the greatest obstacle in
the way Of development Of house paints
of improved life and no fully satisfac-
tory solution is now in sight
"One promising possibility is to
paint the back of the clapboard SO that
the side toward the house is protected
from moisture as we'll as the side to-
ward the weather. This has aroused
considerable interest in the possibility
of mill priming of both sides of clap
boards and the use of some Of the
newer high-impermeability synthetic
finishes for at least the backs of the
clapboards may prove valuable. 1t is
probable that the eventual develop
ment of house paints of longer life may
hinge upon the development Of con-
struction methods which will mini.
mize the collection of moisture on the
back Of the siding"