Causes and Treatment of Bubbles in Float Glass

The production technology of float glass has matured over decades of development, but bubbles remain the most difficult defect to deal with in float glass production. Their presence not only greatly affects the aesthetics, uniformity, and light transmission of float glass, but also severely impacts the production yield of float glass.

According to their source of origin, bubbles can roughly be divided into two types:

The first type is process-related bubbles, including primary bubbles and secondary bubbles. Primary bubbles are also called a molten clear bubble, and its causes generally come from: 1) Abnormal quality of raw materials in the mix (particle size exceeding the upper or lower limit, unreasonable particle size distribution of each raw material, etc.) or unreasonable mix sheet settings (composition, etc.); 2) The melting and clarifying temperatures of the furnace are unreasonable, causing bubbles to be unable to fully escape or be absorbed by the molten glass; 3) The clearing time of the glass liquid is too short, not allowing sufficient time for the bubbles to be released or absorbed; 4) Improper control of the atmosphere inside the melting furnace affects the rate at which bubbles are released. The main solution during the production process is generally to appropriately increase the clarification temperature and adjust the amount of clarifying agent, so that bubbles can be expelled during the melting clarification stage and dissolved and absorbed during the cooling stage after the hot spots. Secondary bubbles, also known as regenerated bubbles, occur because the conditions of the glass melt, which has completed the clarification process, change (such as temperature, furnace pressure, or furnace operating conditions), causing reboiling and releasing the bubbles dissolved within it again. Generally, this issue is mainly resolved by optimizing the process parameters.

The second type is non-process-related bubbles, also called impurity bubbles, mainly including air bubbles, refractory material bubbles, and contamination bubbles. These bubbles require comprehensive analysis, and targeted measures should be taken for resolution and control based on the actual situation.