The main applications of sodium silicates are in detergents, paper industry (as a
deinking agent), water treatment, and construction materials. and have been widely used at least since the
First World War. The largest application of sodium silicate solutions is a cement for producing
cardboard. or a silicon dioxide–covered silicon wafer to one another. Sodium silicate glass-to-glass bonding has the advantage that it is a low-temperature bonding technique, as opposed to fusion bonding. which requires an intermediate layer such as
silicon nitride (SiN) to act as a diffusion barrier for sodium ions. This lack of field assistance can sometimes be beneficial, because field assistance can provide such high attraction between wafers as to bend a thinner wafer and collapse
Dyes Sodium silicate solution is used as a fixative for hand dyeing with
reactive dyes that require a high pH to react with the textile fiber. After the dye is applied to a cellulose-based fabric, such as cotton or rayon, or onto silk, it is allowed to dry, after which the sodium silicate is painted on to the dyed fabric, covered with plastic to retain moisture, and left to react for an hour at room temperature.
Repair work Sodium silicate is used, along with
magnesium silicate, in
muffler repair and fitting paste. Magnesium silicate can be mixed with a solution of sodium silicate to form a thick paste that is easy to apply. When the
exhaust system of an internal combustion engine heats up to its
operating temperature, the heat drives out all of the excess water from the paste. The
silicate compounds that are left over have glass-like properties, making a temporary, brittle repair that can be reinforced with glass fibre. Sodium silicate can be used to fill gaps in the
head gasket of an engine. This is especially useful for
aluminium alloy cylinder heads, which are sensitive to thermally induced surface deflection. Sodium silicate is added to the cooling system through the
radiator and allowed to circulate. When the sodium silicate reaches its "conversion" temperature of , it loses water molecules and forms a glass seal with a re-melting temperature above . This repair can last two years or longer, and symptoms disappear instantly. However, this repair works only when the sodium silicate reaches its "conversion" temperature. Also, sodium silicate (glass particulate) contamination of lubricants is detrimental to their function, and contamination of engine oil is a serious possibility in situations in which a coolant-to-oil leak is present. Sodium silicate solution is used to inexpensively, quickly, and permanently disable automobile engines. Running an engine with half a U.S. gallon (or about two liters) of a sodium silicate solution instead of
motor oil causes the solution to
precipitate, catastrophically damaging the engine's bearings and pistons within a few minutes. In the United States, this procedure was used to comply with requirements of the
Car Allowance Rebate System (CARS) program.
Construction A mixture of sodium silicate and
sawdust has been used in between the double skin of certain
safes. This not only makes them more
fire resistant, but also makes cutting them open with an
oxyacetylene torch extremely difficult due to the
smoke emitted. Sodium silicate is frequently used in
drilling fluids to stabilize and avoid the collapse of
borehole walls. It is particularly useful when drill holes pass through
argillaceous formations containing swelling
clay minerals such as
smectite or
montmorillonite.
Concrete treated with a sodium silicate solution helps to reduce
porosity in most
masonry products such as
concrete,
stucco, and
plasters. This effect aids in reducing water penetration, but has no known effect on reducing water vapor transmission and emission. A chemical reaction occurs with the excess Ca(OH)2 (
portlandite) present in the concrete that permanently binds the silicates with the surface, making them far more durable and water repellent. This treatment generally is applied only after the initial
cure has taken place (approximately seven days depending on conditions). These
coatings are known as
silicate mineral paint. An example of the reaction of sodium silicate with the calcium hydroxide found in concrete to form
calcium silicate hydrate (CSH) gel, the main product in hydrated Portland cement, follows. : + + → +
Crystal gardens When crystals of a number of metallic salts are dropped into a solution of water glass, simple or branching
stalagmites of colored metal silicates are formed. This phenomenon has been used by manufacturers of toys and chemistry sets to provide instructive enjoyment to many generations of children from the early 20th century until the present. An early mention of crystals of metallic salts forming a "
chemical garden" in sodium silicate is found in the 1946
Modern Mechanix magazine. Metal salts used included the sulfates and/or chlorides of copper, cobalt, iron, nickel, and manganese.
Sealants Sodium silicate with additives was injected into the ground to harden it and thereby to prevent further leakage of highly radioactive water from the
Fukushima Daiichi nuclear power plant in Japan in April, 2011. The residual heat carried by the water used for cooling the damaged reactors accelerated the setting of the injected mixture. On June 3, 1958, the
USS Nautilus, the world's first nuclear submarine, visited Everett and Seattle. In Seattle, crewmen dressed in civilian clothing were sent in to secretly buy 140 quarts (160 liters) of an automotive product containing sodium silicate (originally identified as Stop Leak) to repair a leaking condenser system. The
Nautilus was en route to the North Pole on a top secret mission to cross the North Pole submerged.
Firearms A historical use of the adhesive properties of sodium silicates is the production of
paper cartridges for black powder revolvers produced by
Colt's Manufacturing Company between 1851 and 1873, especially during the
American Civil War. Sodium silicate was used to seal combustible nitrated paper together to form a conical paper cartridge to hold the black powder, as well as to cement the lead ball or conical bullet into the open end of the paper cartridge. Such sodium silicate cemented paper cartridges were inserted into the cylinders of revolvers, thereby speeding the reloading of cap-and-ball black powder revolvers. This use largely ended with the introduction of Colt revolvers employing brass-cased cartridges starting in 1873. Similarly, sodium silicate was also used to cement the top wad into brass
shotgun shells, thereby eliminating any need for a crimp at the top of the brass shotgun shell to hold a shotgun shell together. Reloading brass shotgun shells was widely practiced by self-reliant American farmers during the 1870s, using the same waterglass material that was also used to preserve eggs. The cementing of the top wad on a shotgun shell consisted of applying from three to five drops of waterglass on the top wad to secure it to the brass hull. Brass hulls for shotgun shells were superseded by paper hulls starting around 1877. The newer paper-hulled shotgun shells used a roll crimp in place of a waterglass-cemented joint to hold the top wad in the shell. However, whereas brass shotshells with top wads cemented with waterglass could be reloaded nearly indefinitely (given powder, wad, and shot, of course), the paper hulls that replaced the brass hulls could be reloaded only a few times.
Food and medicine Sodium silicate and other silicates are the primary components in "instant" wrinkle remover creams, which temporarily tighten the skin to minimize the appearance of wrinkles and under-eye bags. These creams, when applied as a thin film and allowed to dry for a few minutes, can present dramatic results. This effect is not permanent, lasting from a few minutes up to a couple of hours. It works like water cement, once the muscle starts to move, it cracks and leaves white residues on the skin. Waterglass has been used as an egg preservative with large success, primarily when refrigeration is not available. Fresh-laid eggs are immersed in a solution of sodium silicate (waterglass). After being immersed in the solution, they are removed and allowed to dry. A permanent air tight coating remains on the eggs. If they are then stored in appropriate environment, the majority of bacteria which would otherwise cause them to spoil are kept out and their moisture is kept in. According to the cited source, treated eggs can be kept fresh using this method for up to five months. When boiling eggs preserved that way, the shell is no longer permeable to air, and the egg will tend to crack unless a hole in the shell is made (e.g., with a pin) in order to allow steam to escape. Sodium silicate's
flocculant properties are also used to clarify wine and beer by precipitating colloidal particles. As a clearing agent, though, sodium silicate is sometimes confused with
isinglass which is prepared from
collagen extracted from the dried
swim bladders of
sturgeon and other fishes. Sodium silicate gel is also used as a substrate for algal growth in
aquaculture hatcheries. ==See also==