It’s easy to make sodium silicate from common home chemicals. Sodium silicate it also called water glass or liquid glass. It is the key ingredient in the Magic Rocks chemical garden, plus it finds use as a paper cement, fireproofing agent, automotive repair agent, and crackle glaze for pottery. Sodium silicate is also a precursor to make silicon compounds.
Sodium Silicate or Water Glass Materials
The two chemicals you react for making sodium silicate are silica gel and sodium hydroxide (NaOH). You don’t need to order pure chemicals for this, since they are readily available as common household materials.
- Silica gel beads or crystal kitty litter (6 grams)
- Drain cleaner or lye (4-8 grams)
- Water (10 ml)
This recipe makes enough water glass for a test tube. If you want a larger volume, use the same ratio of ingredients. For example, you can use 60 grams of silica gel, 40-80 grams of sodium hydroxide, and 100 milliliters of water.
Both silica gel beads and crystal kitty litter are silica. Essentially, this is chemically identical to pure sand or silicon dioxide (SiO2), except it is much more porous and easier to dissolve. Sometimes silica gel beads and kitty litter have blue pieces. The blue comes from cobalt(II) chloride (a moisture indicator) or sometimes just blue dye. If you use the blue pieces, it’s not a big deal for most applications. However, if you want a higher purity product, remove them.
Check the label of the drain cleaner or lye and make sure it is only sodium hydroxide (NaOH). Avoid products that contain metal pieces. Pure sodium hydroxide usually comes as waxy white pellets. Use 4 grams of sodium hydroxide if you’re ultimately making Magic Rocks. Otherwise, use 8 grams (the stoichiometric ratio for aqueous sodium silicate as a product).
Distilled water is best, but not critical. If you don’t have it, use tap water.
How to Make Sodium Silicate
- Crush the silica gel beads or kitty litter. One method is placing it in a plastic bag and smashing it with a hammer or crushing it with a rolling pin.
- Pour the silica gel into a heat-safe glass or ceramic container. Add the water. You may see bubbles, but this is just air escaping from the beads.
- Dissolve the sodium hydroxide in the water a bit at a time. This generates a lot of heat, so slowly add the drain cleaner or lye rather than stirring it in all at once or else the liquid may boil over.
- The starting materials may contain impurities, so filter the hot liquid through a coffee filter or filter paper. Don’t wait until the liquid cools because it becomes thicker.
Once you have the sodium silicate, seal the container and store it for later use. Alternatively, leave the container open to evaporation and eventually grow sodium silicate crystals. As water evaporates and the solution becomes more concentrated, you’ll get pale blue-green sodium silicate crystals. This can take a long time because the solution is viscous and has a low vapor pressure. Don’t apply heat in an attempt to boil off the water and speed up the process or you’ll likely break your original container.
Silica gel is amorphous silicon dioxide (SiO2), while drain cleaner or lye are solid sodium hydroxide (NaOH). The react and yields sodium metasilicate (Na2SiO3), sodium orthosilicate (Na4SiO4), and/or sodium pyrosilicate (Na6Si2O7) and water (H2O).
2NaOH + SiO2 → Na2SiO3 + H2O
4NaOH + SiO2 → Na4SiO4 + 2H2O
6NaOH + 2SiO2 → Na2SiO3 + 3H2O
The stoichiometric ratio for the project is for the first reaction (sodium metasilicate). But, your product may contain various forms of sodium silicate.
Test the Sodium Silicate
When you make chemicals you should test them and make certain the product is what you wanted. This is especially important when reacting home chemicals because their purity may be questionable. Fortunately, there is a simple and fun test for sodium silicate or water glass.
- Pour a bit of sodium silicate into a clear jar. Use an old jar and not cookware.
- Drop a few chunks of copper sulfate into the liquid. Solid copper sulfate is available online or at home supply stores as a pure chemical, mainly as a root killer and pool treatment. Alternatively, use the “rocks” sold as fire colorant crystals. This product contains assorted metal salts.
- Within a few minutes, watch the crystals grow into a chemical garden!
If you see growth, you made sodium silicate. If you don’t get growth then either the starting chemicals were not what you thought they were. It’s as simple as that.
- Read the safety information for the chemicals you use.
- Wear eye protection (goggles) and gloves and avoid contact with the drain cleaner or lye. This chemical is caustic and can cause burns.
- Bechtold, M. F. (1955). “Polymerization and Properties of Dilute Aqueous Silicic Acid from Cation Exchange”. The Journal of Physical Chemistry. 59 (6): 532–541. doi:10.1021/j150528a013
- Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
- Lagaly, Gerard; et al. (2005). “Silicates.” Ullmann’s Encyclopedia of Industrial Chemistry. Wiley-VCH. doi:10.1002/14356007.a23_66
- Modern Mechanix (April 1946). “Magic Garden.”