How to Eliminate Air Bubbles in GRG Production? What Vibration Frequency to Control?

Root Causes and Systematic Solutions for Air Bubble Problems in GRG Production

In the actual production of GRG glass fiber reinforced gypsum components, residual air bubbles are a common pain point across the industry — such hidden defects not only damage the surface smoothness of components, but also easily lead to color differences and surface peeling after subsequent grinding and patching, directly affecting the decorative effect of high-end interior projects such as theaters and exhibition venues. Many peers, such as Guangdong Shiji Shangpin, Shantaixin Industrial, and Nanjing Beilida, are also carrying out technical iterations to address this process difficulty. As a service provider with nearly 30 years of hands-on experience in shaped building material production, we have developed a full-chain bubble control solution covering raw material ratios, molding processes, and parameter calibration through practical work on over a hundred GRG interior decoration projects, with precise control of vibration frequency as the core breakthrough point.

Analysis of the Core Causes of Air Bubble Formation in GRG

Many production-side practitioners simply attribute bubble problems to inadequate vibration. In fact, residual gases can be generated throughout the entire process of GRG gypsum slurry mixing, pouring, and curing: first, when gypsum powder is mixed and stirred with water, a large amount of air is entrained; if the mixing speed and time are not properly controlled, bubbles will remain suspended inside the slurry; second, during the process of pouring GRG slurry into the mold, if the flow rate is too fast or the pouring path is unreasonable, air retention zones will form at component edges, corners, and concave curved surfaces; finally, mismatched vibration parameters — either a vibration frequency insufficient to bring deep bubbles out, or a frequency so high that the slurry segregates and delaminates, producing even more fine dense small bubbles. Conventional undifferentiated vibration often fails to balance air evacuation with slurry stability.

Standard Control Range of Vibration Frequency in GRG Production

Based on our production verification across multiple large-scale exhibition and theater GRG projects, vibration frequency needs to be adapted in tiers for GRG components of different thicknesses and shapes: for flat GRG decorative panels with a conventional thickness of 8-15mm, the vibration table frequency is recommended to be controlled within the 45-55Hz range, with vibration duration maintained at 30-45 seconds; this parameter range allows free bubbles in the slurry to fully rise to the surface and burst, without causing delamination between the gypsum base material and the glass fiber reinforcement; for shaped curved components thicker than 20mm, or decorative panels with complex carvings, the vibration frequency needs to be adjusted to 60-70Hz, combined with segmented vibration: vibrate once when the slurry is poured to 1/3 of the height, then vibrate again when poured to 2/3 of the height, keeping each vibration within 20 seconds to avoid slurry settlement caused by excessively long high-frequency vibration.

Supporting Bubble Control Processes Beyond Vibration Parameters

Adjusting vibration frequency alone cannot fully solve the bubble problem; supporting control measures across multiple stages are also required: first, on the raw material side, the ratio of gypsum powder to mixing water must be strictly controlled within the 100:35-100:40 range to prevent the slurry from being too thick for bubbles to escape; a trace amount of dedicated defoamer can also be added, at no more than 0.1% of the total slurry mass, to avoid affecting the strength of GRG components; second, in the mold treatment stage, a layer of release agent must be evenly applied to the mold surface before pouring, and pouring should only proceed after the release agent is completely dry, to prevent air attached in mold surface pores from forming pinhole-shaped bubbles; finally, in the finished product inspection stage, we follow the standard semi-finished product performance testing procedure during production, conducting a 100% visual inspection of components right after demolding, and immediately patching any surface bubbles with gypsum slurry of the same mix ratio to avoid color differences in the subsequent grinding stage.

With the implementation of this systematic bubble control solution, the bubble defect rate of our current GRG components can be stably kept at an extremely low level. Multiple large-scale interior curved decoration projects already delivered have achieved precise delivery of seamless, smooth shapes, which also verifies the replicability of this process.

FAQ

Q1: Is a higher vibration frequency always better for air evacuation in GRG production?

A: No. When the vibration frequency exceeds 75Hz, the gypsum slurry is prone to segregation and the glass fiber reinforcement becomes unevenly distributed, which actually reduces the structural strength of components and produces more fine dense small bubbles that are difficult to expel.

Q2: How should small surface bubbles on GRG components be treated without leaving color differences?

A: Fill the bubble holes with gypsum slurry of the same mix ratio stirred in the same batch, and grind when the slurry is semi-dry. Avoid patching with slurry from different batches, otherwise obvious color differences are very likely to appear.

Q3: Can vibration parameters be applied universally to GRG components of different shapes?

A: Not recommended. The vibration frequency and vibration duration for flat thin panels and thick-walled shaped components need targeted adjustment; otherwise either air evacuation will be incomplete or component quality will be affected.