Sophisticated adhesives,
sealants and coatings are two-component systems. One part has to be mixed with
another part before they are applied. After a while, a chemical reaction takes
place, and what is created is a filler, paint or glue with exceptional
properties. It is not possible to obtain those properties by taking some simple
thing out of a can.
Each of these two parts, whether they are liquids or pastes, consists of very
small components called
molecules. The manufacturer designed the system so that the individual
molecules of each component would react with each other in certain proportions.
That is why the instructions say to mix the materials in those proportions.
If the materials are mixed in
different proportions, then some molecules of one or another component are left
over, scattered among the molecules of both components that did react together.
In that case, the material will be softer or weaker than it should be, or will
soften in water when it should not. It might be a gooey mess. It is therefore
important to mix the components thoroughly, so that everywhere in the mixture
the ingredients are in the correct proportions, even down to the individual
molecules.
We make Fill-It parts A and B
different colors to make it easy to thoroughly mix the product. When you can
see the streaks of different colors you know you must continue to smear,
scrape, fold and mix until the color is uniform. The mixing tools themselves
must be scraped occasionally. If mixing a paste on a flat surface, the mixing
surface itself must occasionally be scraped off. When mixing liquids in a
container, mix thoroughly in one container and then scrape out the entire
contents into a second container and mix again.
If there are any soft or
gooey spots in the final cured product, which is proof that the material was
not thoroughly mixed.
Making Coatings Stick Better
All woods consist of
cellulose fibers bonded together by a natural resin which acts as glue,
Typically seven to fifteen percent moisture is present (chemically attached to
the cellulose) depending on average humidity, There is also a varying amount of
"sap", which is a complex mixture of different oils and resins.
Hardwoods such as oak have different resins than softwoods such as fir.
In order to obtain a good
bond between wood and any paint or adhesive, the fibers on the surface of the
wood must be strongly bonded to each other and to the adhesive or coating. The
surface of wood is microscopically rough, with many surface fibers loosely
attached to the bulk of the wood underneath. Glues and the liquid portion of
paints can soak into porous wood surfaces. This can produce a paint with most
of the pigment on the surface and most of the paint resin soaked into the wood,
and such a resin starved coating will soon fail. It can also leave the glue
joint starved for glue and hence weakened. Therefore a sealer is important in
order to obtain good adhesion between wood and paints. Epoxy resin systems do
not readily dissolve water, but Clear Penetrating Epoxy Sealer (CPES) contains
a high percentage of alcohol in order to dissolve not only the moisture in
woods but also the sap and oils.
The fungus that causes dry
rot retains a lot of moisture and inhibits effective penetration of sealers
that cannot dissolve water. Mildly dry-rotted areas can be epoxy-impregnated
very effectively by CPES since it can dissolve water.
It is not unusual for varnish
to peel off of wood in six to eighteen months, even when a top-quality varnish
is used. Varnish is highly refined oil-base enamel paint without pigments.
Neither varnish. enamel or latex paints are particularly aggressive adhesives.
Our epoxy products are very aggressive adhesives.
Now we have a very important
concept: If we apply something over a surface to which CPES was previously
applied, but before the CPES is (roughly) half-cured, the second material
proceeds to cure first, and the resin film of the CPES cures last, gluing down
the second material. This is why CPES is such an effective adhesion-promoting
primer for varnish.
The particular resins used in
Smith & Co. products are substantially derived from wood itself because
these particular resins, when they cure, will have a toughness and flexibility
that is comparable to the original wood. The fact that the surface is dry to
the touch does not mean that the resin is cured. See Product sheets for
specific curing times.
The modern use of the word
primer has become a non-specific term used broadly and irresponsibly by most
paint manufacturers. Literally, a primer was to be the prime coat, or first
coat. This derives from the Latin primus, meaning first. Products now available
in the marketplace include adhesion promoting primers, waterproofing primers
used to seal a porous substrate, filler primers, sanding and surfacing primers,
corrosion inhibiting primers for metal,
wood primers intended to block tannin bleed-through of wood topcoats,
moisture-diffusion-barrier primers, and probably others. Adding specific
adjectives to the word primer conveys a clear concept.
When sufficient CPES is
applied to the wood in one application to completely saturate the wood, a thin
film of the mixed resins of CPES is left on the surface. The CPES glues down
the varnish, and the ultraviolet absorbers in the varnish protect the epoxy and
the wood from degradation by sunlight. From what our customers tell us, the
typical life expectancy of a good quality varnish, applied in this manner, is
two years or more.
When using clear topcoats such as varnish or
polyurethane it is important to know that the ultraviolet absorbers used in all
clear coatings are sacrificial. They will eventually die. Therefore, more coats
give a longer life. When the ultraviolet absorbers finally "bum out",
the ultraviolet from the sun passes through the clear topcoat and attacks both
the CPES resin and the underlying wood, breaking down the cellulose fibers. The
coating eventually fails as the material beneath it swells and decomposes.
Clear epoxy products are not
chemically compatible with ultraviolet absorbers, and so epoxy coatings are not
used as clear finish coats.
In pigmented coatings the
pigments block the ultraviolet. Because the pigments are chemically stable
minerals, they do not "burn out" and so this failure mechanism does
not exist. Enamel and latex or urethane paints will therefore last longer than
clear urethane or varnish coatings, although high quality clear coatings can
last several years. Latex paints, alkyd enamels, urethane coatings and varnish
can adhere better and last longer with Clear Penetrating Epoxy Sealer applied
to the wood first.
The manufacturers often
changes paint formulations. Always do a small test with new product
combinations to ensure everything works together.
Frequently Asked Questions
Q: How much of the old paint will I have to remove?
A: Perhaps 95%. Clear
Penetrating Epoxy Sealer will not soak through old paint, but if the remaining
paint on the wood is in spots smaller than 1/4" 1/8" the CPES will
soak around and under the old paint. It may, however, cause the edges of the
old paint to curl up. You may have to sand the wood and apply CPES again.
Q: How much rot do I have to remove before applying the sealer?
A: Whatever can be scrabbled away with the bare
finger tips should definitely be removed. Light brushing with a wire brush
easily removes badly deteriorated wood.
Q: Do I have to use the sealer
first before I use the filler?
A: Yes. After applying the
sealer, wait until the wood no longer smells strongly of solvents before
applying the filler.
This will take at least a day and may take a week, depending on the extent of
deterioration
and how deeply the CPES soaked in. Do not apply filler on top of freshly
impregnated wood.
Q: How soon can I paint the filler? Do I have to
prime it?
A: The filler cures overnight and should be sanded
before painting. CPES is an excellent adhesion-promoting primer for paint when
the topcoat needs a primer, although most primers can be used.
Q: How long is the shelf life?
A: At least a year, if the containers are closed
after use.
Q:Can I use it inside?
A: Yes, but you must provide adequate ventilation
such as an exhaust fan in the window. It is also a good idea to wear a mask
with an organic vapor filter cartridge when working with chemicals or solvents.
Q: Does it meet the Air
Quality Management District regulations?
A: Yes.
Q: Will this pass inspection?
A: The inspector usually stabs the wood with a
screwdriver to see how easily it penetrates. After proper restoration the
repairs will feel the same as new wood.
