AGRM News

Innovation and Technology

Russian

info@agrmeng.com

Glass Clarifying Agents

Glass clarifying agents are commonly used auxiliary chemical materials in glass production. Any material that can decompose at high temperatures (gasify) during the glass melting process, producing gas or reducing the viscosity of the glass melt to facilitate the elimination of bubbles in the glass melt, is called a clarifying agent. According to the mechanism of glass clarification, they can be divided into oxygen clarification, sulfur clarification, halide clarification, and composite clarification. Clarifying agents can be classified into oxide clarifying agents, sulfate-based clarifying agents, halide clarifying agents, and composite clarifying agents.

Oxide Clarifying Agents: The main oxide clarifying agents include white arsenic, antimony oxide, sodium nitrate, ammonium nitrate, and cerium dioxide.
  1. White Arsenic (Arsenic Trioxide), also known as white arsenic, is a commonly used clarifying agent known in the glass industry as the “clarification king.” However, to achieve effective clarification, it must be used in combination with nitrates. White arsenic is sparingly soluble in cold water, readily soluble in hot water, highly toxic, and appears as white crystalline powder or amorphous glassy substance. Arsenic ash, a byproduct of gold refining, is often gray-white, gray, or gray-black. Crystalline white arsenic is commonly used as a clarifying agent. When white arsenic is heated to temperatures above 400 degrees Celsius, it releases oxygen, generated by its reaction with nitrates at high temperatures, forming arsenic pentoxide. Heating it to 1300 degrees Celsius causes arsenic pentoxide to decompose into arsenic trioxide, reducing the partial pressure of gases in the glass melt. This process promotes bubble growth and accelerates bubble elimination, achieving the purpose of clarification.The typical dosage of white arsenic is generally 0.2% to 0.6% of the batch weight, with nitrates introduced at 4-8 times the amount of white arsenic used. Excessive use of white arsenic not only increases volatility but also poses environmental pollution and is harmful to humans. Just 0.06 grams of white arsenic can be fatal, so it should be stored and handled by trained personnel to prevent poisoning incidents. Glass using white arsenic as a clarifying agent can lead to reduction and darkening during lampworking operations, so it should be used sparingly or avoided in lampworking glass.
  2. Antimony Oxide: The clarifying effect of antimony oxide is similar to that of white arsenic, and it also requires combination with nitrates. Antimony oxide has a lower decomposition temperature than white arsenic, making it a common clarifying agent in the production of lead glass. In soda-lime-silicate glass, using 0.2% antimony oxide and 0.4% white arsenic as clarifying agents results in effective clarification and prevents the formation of secondary bubbles.
  3. Nitrates: Nitrates are rarely used as standalone clarifying agents in glass; they are generally used as oxygen suppliers in combination with variable valence oxides.
  4. Cerium Dioxide: Cerium dioxide has a higher decomposition temperature and is considered a good clarifying agent. It can be used as a clarifying agent without the need for nitrates since it self-decomposes at high temperatures, releasing oxygen and accelerating clarification. To reduce costs, it is often combined with sulfates in the production of glass beads to achieve effective clarification. Currently, it is widely used as a raw material in composite clarifying agents.
Sulfate-Based Clarifying Agents:

In glass production, the main sulfates used are sodium sulfate, barium sulfate, and calcium sulfate. Sulfates have relatively high decomposition temperatures, making them high-temperature clarifying agents. When sulfates are used as clarifying agents, it is advisable to combine them with oxidizing agents such as nitrates. They should not be used in conjunction with reducing agents to prevent low-temperature decomposition of the sulfates. Sulfates are commonly employed in container glass and flat glass manufacturing, with typical dosages ranging from 1.0% to 1.5% of the batch weight.

Halide Clarifying Agents

Halide clarifying agents primarily include fluorides, sodium chloride (table salt), and ammonium chloride.

  • Fluorides: The main fluorides used are fluorspar and sodium fluoride. The dosage of fluorspar as a clarifying agent is generally calculated at 0.5% of the total batch materials introduced. Sodium fluoride is typically used at a dosage of 0.4% to 0.6% of the amount of sodium oxide in the glass. During the melting process, some of the fluorides may generate hydrogen fluoride, silicon fluoride, and sodium fluoride, which are more toxic than sulfur dioxide. Therefore, the potential environmental impact should be considered when using fluorides.
  • Sodium Chloride (Table Salt): Sodium chloride, when volatilized at high temperatures, can promote glass melt clarification. It is typically used at dosages ranging from 1.3% to 3.5% of the total batch materials. Excessive usage can lead to glass emulsification. Sodium chloride is commonly used as a clarifying agent for boron-containing glasses.
Composite Clarifying Agents

Composite clarifying agents utilize the advantages of oxygen clarification, sulfur clarification, and halide clarification within a clarifying agent. They fully leverage the synergistic and cumulative effects of these components, achieving sustained clarification that greatly enhances the clarifying capacity, surpassing what can be achieved with single clarifying agents. Composite clarifying agents can be categorized into two groups: those containing arsenic (arsenic-antimony composite clarifying agents) and those without arsenic (arsenic-free composite clarifying agents).

Based on their development stages, composite clarifying agents are divided into three generations: the first generation, the second generation, and the third generation, also known as the new generation of environmentally friendly composite clarifying agents. The third generation is renowned for its green, environmentally friendly, safe, and efficient characteristics, making it the future direction of the glass clarifying agent industry. It is also a definite trend in achieving arsenic-free glass formulations. The typical dosage of composite clarifying agents ranges from 0.4% to 0.6% of the batch weight.

Composite clarifying agents have found widespread use in the glass industry, particularly in container glass, glass beads (alkali-free and medium-alkali), pharmaceutical glass, lighting glass, electronic glass, microcrystalline glass, and other glass products. Manufacturers of composite clarifying agents are primarily concentrated in regions such as Hunan, Sichuan, and Jiangsu.

Composite clarifying agents refer to composite glass clarifying agents used in the glass industry. They are formulated by rationally combining two or more materials that can release gas through high-temperature decomposition or gasification during the glass melting process, facilitating the removal of gases from the glass melt.

Composite clarifying agents can be categorized based on the presence of arsenic: arsenic-antimony composite clarifying agents and arsenic-free composite clarifying agents. Arsenic-free composite clarifying agents represent a new generation of environmentally friendly glass clarifying agents, aligning with the industry’s drive towards arsenic-free glass formulations.

Composite clarifying agents can also be classified based on their primary effective components, including arsenic-based, arsenic-antimony-based, and cerium-based composite clarifying agents.

Moreover, composite clarifying agents can be categorized by their development stages: the first generation, the second generation, and the third generation. The third generation is characterized by the utilization of variable valence oxides, sulfides, halides, and their salts in precise combinations, harnessing the combined advantages of oxygen clarification, sulfur clarification, and halide clarification in the glass clarification process. It represents a typical example of the “three-system” clarifying method. The “three-system” clarifying agents are the future direction of the glass clarifying agent industry and an inevitable trend in achieving arsenic-free glass formulations.

General characteristics and usage methods of third-generation composite clarifying agents:

  1. The product is typically suitable for glass melting under oxidative atmospheres.
  2. It effectively prevents “browning” and reduction-related darkening of glass during secondary processing.
  3. It can deliver clarification without the need for strong oxidizing agents, reducing the required amount of nitrates and “selenium-cobalt” colorants.
  4. In boron-containing glasses, it helps inhibit boron volatilization loss.
  5. It exhibits strong synergy with various clarifying agents and can be used in combination with other clarifying agents without side effects.
  6. It is non-toxic, safe, easy to transport, and store.
  7. The typical usage ranges from 0.4% to 0.6% of the batch weight of the powder, allowing for a direct substitution for white arsenic or adjustment based on specific process requirements.

Composite clarifying agents find applications in various areas, including container glass, glass beads (alkali-free and medium-alkali), lighting glass, pharmaceutical glass, microcrystalline glass, electronic glass, and other glass product manufacturing processes.

Desilverization Paste

Desilverization paste is widely used in the deep processing of silvered mirror products such as tea mirrors, black mirrors, and gold mirrors. It is employed for adding patterns, text, logos, and other designs to these mirrors. This material simplifies the process and is highly efficient. The operation is straightforward: simply apply the desilverization paste to the silvered mirror surface and then clean it with water to achieve the desired effect.

The operational steps for using desilverization paste from a certain company are as follows:

  1. First, create the required pattern or lines on plastic adhesive paper, and then affix it to the back of the silvered mirror to outline the design (or use acid-resistant ink for printing) for the next step.
  2. Use a special paint remover or paint cleaning agent to thoroughly remove the paint from the surface of the silvered mirror that needs to be treated. Note: Before using the paint remover, it’s advisable to trace a line around the pattern with a craft knife to separate the areas where paint is to be removed from those where it is not. This leads to a more ideal result.
  3. Apply the desilverization paste (or use silk screen printing in combination) evenly on the surface that needs treatment. Allow it to sit for about 1-2 minutes, and then rinse it off with clean water.

Another company in China has developed a desilverization paste that can remove the protective paint and silver layer from the mirror in one go, simplifying the traditional complex processes. It does not react with regular adhesive paper or protective films, reducing costs and simplifying the operation. The desilverization and paint removal process is fast, and after treatment, the mirror remains clear without any residue or edges.

The operating process for this product is as follows:

  1. First, create the required pattern on plastic adhesive paper and attach it to the back of the mirror. Then, proceed to the next step.
  2. Pour the desilverization and paint removal agent onto the areas of the mirror that need treatment. Let it sit for 4-5 minutes. Afterward, the powerful desilverization and paint removal agent will react fully with the paint and mercury (if there are any spots that haven’t reacted, add more desilverization and paint removal agent). After sufficient reaction, rinse and scrub the mirror surface with tap water (Note: Before desilverizing and removing paint, it’s advisable to outline the pattern with a craft knife to separate the areas where paint is to be removed from those where it is not. This leads to a more ideal result).

Precautions for using this product:

  1. Shake the desilverization and paint removal agent well before use.
  2. If the temperature is low, warm the agent with warm water (30-40°C) for 2-3 minutes.
  3. After paint and silver removal, use a craft knife to trim the edges of the pattern as needed.
  4. When storing this product, use acid-resistant containers (such as plastic buckets, PP boards, PVC boards, etc.), and avoid using metal containers.
  5. Wear acid-resistant gloves during the operation to prevent direct contact of the solution with the skin or eyes.
Message WhatsApp
Top