We try to apply FeS while the stucco is still green--within
days of the final coat. There is still unreacted cement in the
mix, and it's damp, which allows the mixture to penetrate deeper
into the surface. FeS on old concrete or stucco often will have
pale patches where the stain couldn't work.
We begin by wetting the wall thoroughly, and try to keep it
wet while we're working. Again, the idea is to help the solution
penetrate, and it probably promotes a more even finish.
We use the powdered FeS from nurseries, and mix it up in a
5-gal bucket. It's kind of like mixing salt in water. We keep
mixing it in until the FeS starts falling out of solution (crystals
start to show up on the bottom). We stir the mix as we're working
to keep everything in suspension.
You can apply it with most anything--sprayer, brush, roller,
foam brush. Sprayers tend to get clogged pretty easily, and we
usually use a roller and a big floppy brush for small areas.
We apply very generously, and saturate an area before moving
down the wall. If you don't saturate an area, you'll leave roller
marks.
One of the great thrills is watching the owner's face when
their house turns slimey green--the first thing that happens.
It takes an hour or two before the rust color starts to appear.
We usually repeat the process two or three times a day apart--until
additional coats have little noticable effect. The color will
continue to deepen for weeks and months after the application.
Extra FeS crystals will be left on the surface, and the first
rainy season sometimes works that into the wall with some deepening.
Some will leach out with rains, and deep areas of color will
show up where there's lots of runoff--on the sides of window
sills, for instance. This creates a very natural aging appearance
for the building, something which plasterers and painters try
hard to duplicate in faux finishes. FeS is the 'real faux'!
The final color will be influenced by the base coat of stucco.
A white or tinted stucco base will show through and add a particular
cast to the stain color. As always, experiment first. Nothing
takes light quite like a natural stain, and a FeS stained building
glows brilliantly in afternoon sun.
One caution. The stuff leaves a slight hazy film on windows
which we've only been able to remove with lots and lots of elbow
grease. We coat the windows with Rain-X, which is sold in auto
stores for windshields, and have no problem. And FeS will turn
wood grey, just as it stains concrete. Little splashes you don't
notice will show up as grey spots in a few hours. We've used
this to our advantage, and treated wood to give it an old appearance
(and to match new wood with recycled timbers). At Shenoa, we've
frequently had people come and ask us where was the new straw-bale
house! The stone-washed jeans of the construction industry....
Some examples:
Octagonal Barn
Cottage at Shenoa
Round Meditation Space (ferrous
nitrate)
John Swearingen
Skillful
Means
PO Box 207
Junction City, CA 96048