Introduction: With the rapid development of the cosmetics packaging industry, there is an increasing demand for visually appealing packaging in the cosmetics market. Frosted glass bottles, with their noble and elegant appearance, have gained popularity among cosmetics packaging manufacturers and consumers, becoming a prominent material in the cosmetics packaging market. This article provides a brief overview of frosted glass and its related knowledge, serving as a reference for purchasing professionals.

Frosted Glass Process: Chemical frosted glass is essentially a type of acid-etched glass that undergoes chemical corrosion on the glass surface, similar to the principles of chemical etching and chemical polishing.

The difference lies in the fact that in the chemical polishing process, efforts are made to dissolve and rinse off certain insoluble reaction products that adhere to the glass surface after chemical corrosion, resulting in a uniform erosion of the entire surface and obtaining a transparent and smooth surface. On the other hand, chemical frosted glass retains the insoluble reaction products, which adhere to the glass surface. Over time, these reaction products accumulate into solid crystalline particles firmly attached to the surface, hindering further acid corrosion reactions. As a result, an uneven erosion occurs, producing a semi-transparent frosted surface. This frosted surface scatters incident light, creating a semi-transparent and hazy effect, hence the name “frosted.”

  1. Frosted Glass Characteristics: Frosted glass is achieved through a chemical etching process, where insoluble reaction products form small particle crystals firmly attached to the glass surface. The degree of erosion varies due to the different contact levels between the glass surface, the gaps between particles, and the acid solution. This results in an uneven surface texture, belonging to surface chemical treatment. By controlling the size and quantity of crystals adhered to the glass surface, different levels of rough or delicate frosted finishes can be obtained.
  2. Determining the Degree of Frosted Effect: Scattering Rate: The higher the scattering rate of the glass surface, the higher the degree of frosting.

Total Transmittance: In addition to scattering, reflecting, and absorbing incident light, glass transmits the remaining light. Colorless glass has a relatively low absorption rate for visible light, and for the same type and composition of colorless transparent glass with the same thickness, the total transmittance before frosting remains almost unchanged. Therefore, the total transmittance can be used as an approximate representation of the glass’s scattering rate, with lower total transmittance indicating a higher degree of frosting.

Surface Morphology: It mainly refers to the size and distribution of the etched product particles on the glass surface after acid corrosion, which not only affects the total transmittance but also influences the surface’s smoothness. If the distribution of etched product particles on the surface is sparse, the total transmittance is higher. Conversely, if the distribution is dense, the total transmittance is lower.

3. Sandblasting Method and Chemical Etching Materials

1) Sandblasting Method
– Immersion Method: Glass products are immersed in sandblasting solution for a certain period of time.
– Spray Method: Sandblasting solution is sprayed onto the glass surface.
– Coating Method: Sandblasting paste is applied to the surface of glass products.

2) Chemical Etching Materials
– Sandblasting Solution: A liquid prepared from hydrofluoric acid and additives.
– Sandblasting Powder: A powdered material prepared from fluorides and additives. When used, sulfuric acid or hydrochloric acid is added to generate hydrofluoric acid. Essentially, it belongs to the category of sandblasting solution.
– Sandblasting Paste: A paste made by mixing fluorides with acid or by mixing hydrofluoric acid and additives.

Note: Hydrofluoric acid, if properly proportioned, can be effective, and the sandblasting process requires less time compared to sandblasting paste or powder. However, hydrofluoric acid is not suitable for large-scale production, especially in hot weather, as its operation is highly unstable and it easily evaporates into the air, causing pollution to the environment. Moreover, hydrofluoric acid is highly hazardous to human health, as it can corrode the skin and bones. It is gradually being phased out as a sandblasting method.

Both sandblasting paste and sandblasting powder are suitable materials for sandblasting glass products, but they are used with different methods. They complement each other and have their roles in the glass industry.

Sandblasting paste is more suitable for localized sandblasting of glass products and is easier to handle. However, it is not suitable for large-area glass sandblasting mainly because it can easily result in uneven sandblasting surfaces. Sandblasting paste is commonly used in screen printing.

Compared to sandblasting paste, the operation process for sandblasting powder is slightly more complex as it needs to be prepared as a solution. However, sandblasting powder is suitable for almost all types of glass products. It can be used for sandblasting glass items that can be soaked in the solution, such as glass cups, glass bottles, glass decorations, as well as for glass products like flat glass and sliding door glass that cannot be immersed in sandblasting solution but still require sandblasting.

4. Difference between Sandblasted Glass and Frosted Glass

Sandblasted Glass:
It is produced by using high-speed jets of glass sand particles to strike the glass surface, creating a subtle unevenness that results in a hazy effect, refracting light. Finer glass sand particles create a higher level of three-dimensional effect. Compared to frosted glass, the surface of glass products processed using the sandblasting technique has a rougher texture, higher damage rate, larger dust contamination, and generally involves moderate difficulty in the process.

Frosted Glass:
Also known as satin glass or matte glass. It is made by treating ordinary flat glass through methods such as mechanical sandblasting, manual grinding, or hydrofluoric acid etching to achieve a uniform surface. Due to its rough surface, it diffuses light through diffuse reflection, providing a soft and non-glare appearance. Very thin glass is not suitable for frosted treatment.

5. Sandblasting Precautions

1) Sandblasting solution must be prepared in plastic or corrosion-resistant metal containers.
2) Rubber gloves should be worn when using it to prevent skin burns. In case of accidental skin contact, rinse promptly with water.
3) The surface of glass products must be thoroughly cleaned.
4) The amount of acid added should be adjusted according to the different glass materials, and water should be added before sulfuric acid.
5) The sandblasting solution should be thoroughly stirred before use and covered when not in use.
6) During the use of the sandblasting solution, it is necessary to add sandblasting powder and sulfuric acid in a timely manner.
7) The wastewater generated in production can be neutralized with lime before discharge.

6. Applications of Sandblasting

The cosmetic packaging industry uses sandblasted bottles as the main material for cosmetic packaging, as their elegant and sophisticated appearance is favored by a large number of cosmetic consumers. The glass surface after sandblasting contains extremely fine sandblasting particles, providing a delicate touch and emitting a lustrous shine similar to that of beautiful jade. Moreover, the inherent stability of glass effectively prevents chemical reactions between cosmetics and the packaging bottle under light exposure, thus ensuring the quality of cosmetics.