Create Synthetic Opal: Stober & Silica Gel Methods

[TalonD]

What chemicals and what process would you need to make synthetic opal? I have heard of the Stober method. Also I have heard of using silica gel. But I haven't found much information on either. Are there any common easily available chemicals that the average non chemist could obtain and make synthetic opal?

 

[chemisttree]

Here's one method:

First, you add a little ethyl silicate into boiled weak alkaline solution and colloidal silica will grow. After separating and eliminating the condensed coarse spheres, by a sedimentation method, you drip ethyl silicate through a cooling installation and you grow amorphous silica spheres using colloidal silica as seed. You need a few months to get growth of uniform spheres and also you have to check the growing spheres all the time by a spectrometer. For this purpose, checking and modifying the temperature, density, and pH of the solution is very important. You stop the dripping of the ethyl silicate when sphere diameter becomes around 550nm. Then you continue to boil them a few more days and the effects are concluded.

After you collect and remove alchohol by distillation, you transfer the suspending solution, which contains the grown-up spheres into the clear container, such as a beaker. Then you let them settle down quietly over a long period of time. It takes a few months for the spheres to settle into a regular pattern. Centrifugal force cannot be used to accelerate settling of spheres. A few months later you will see the play of color displayed by the settled spheres in the beaker.

After you aspirate and remove most of the upper solution, you must add some more fluid containing colloid silica and stir the spheres up then for a second time to allow settlement start. First, settled spheres in the beaker become the cores and the later settlings grow upward as columns. At this time, the superior column eliminates the inferior column. In mineralogy, we explain these as geometric selection (Grigorlev 1965) and honeycomb color patterns get larger and larger.

The settled spheres exist in gel conditions and moisture is only slowly removed by natural evaporation so that dryness takes a long time. The gel turns into solid condition by the heat treatment until the gel becomes silica-stacked spheres of amorphous silica. Under this process, you can make black opal and transparent crystal opals by adding several additives. It takes about one year for the whole process.

Sounds a bit complicated for an at home experiment. Have you a spectrometer at home?

 

[quicknote]

I am familiar with the process of creating synthetic opal using the Stober and silica gel methods. Both methods involve the use of chemicals and a specific process to produce synthetic opal.

In the Stober method, the main chemicals needed are tetraethyl orthosilicate (TEOS), ammonia, and water. These chemicals are mixed together in a specific ratio and heated to form a solution. Next, a mineralizing agent such as sodium hydroxide or potassium hydroxide is added to the solution to initiate the formation of silica particles. These particles then grow and form the opal structure. The Stober method is relatively simple and can be carried out with basic laboratory equipment.

The silica gel method also requires the use of TEOS, but it also utilizes a gel-forming agent such as sodium silicate. The chemicals are mixed together and heated to form a gel, which is then allowed to dry and harden. The gel is then heated again to remove any remaining water and form the opal structure. This method requires more specialized equipment and expertise.

Both methods require the use of specific chemicals and precise measurements to produce high-quality synthetic opal. These chemicals may not be readily available to the average non-chemist, and the process itself can be complex and potentially dangerous without proper training and equipment.

However, there are alternative methods for creating synthetic opal that may be more accessible to the average person. For example, some people have reported success using a mixture of water, ethanol, and nail polish to create a DIY version of synthetic opal. While this method may not produce the same high-quality results as the Stober or silica gel methods, it can be a fun and accessible way to create a unique piece of jewelry.

In conclusion, creating synthetic opal requires specific chemicals and a precise process, which may not be easily accessible to the average non-chemist. While there are alternative methods that may be more accessible, it is important to note that the quality and authenticity of the resulting synthetic opal may vary. It is always best to consult with a trained professional and use proper safety precautions when working with chemicals.