Silica Sol vs Water Glass Investment Casting: How to Choose the Right Process for Your Project
Juin 18, 2026
Silica Sol vs Water Glass Investment Casting: How to
Choose the Right Process for Your Project
In the field of precision casting, the choice between water glass investment casting and silica sol investment casting processes directly affects product quality, production costs, and market positioning. As a comprehensive enterprise integrating precision casting, sand casting, forging, and machining, Baoding Langway Trading Co., Ltd. has been deeply involved in this field for many years and has a profound understanding of the differences between the two processes.
I. The essence of the process: the difference from the perspective of chemical principles
The silica sol investment casting process uses silica microparticles as a binder, forming a robust siloxane network through dehydration and condensation between the particles, maintaining excellent strength even at high temperatures of 1200-1300℃. The water glass process, on the other hand, uses an aqueous sodium silicate solution as a binder, forming a gel through CO₂ hardening, but its strength drops sharply around 800℃.
This fundamental difference in chemical composition directly determines the final quality of the casting.
II. Quality Showdown: The Difference Between Precision and Surface Finish
Silica sol technology is synonymous with “near-net-shape forming”: surface roughness can reach Ra 1.6-3.2μm; dimensional tolerances can be controlled within CT4-6 grade; many parts can be used directly without machining;
Le water glass process presents significant differences: surface roughness is typically Ra 6.3-12.5μm; dimensional tolerances are CT7-9; and sufficient machining allowance must be reserved.
Furthermore, water glass mold shells lack high-temperature strength, are prone to defects such as sand adhesion and burrs during casting, and the sand removal process is quite difficult. In contrast, silica sol mold shells effectively resist the erosion of molten metal, resulting in clear casting contours and a significantly reduced defect rate.
Ⅲ. Cost is not only the cost of processes, but also the total cost of the project.
In terms of material and shell-making costs, the silica sol process requires high-value materials such as zircon sand and mullite, and the shell-making cycle takes 3-5 days; the water glass process uses inexpensive materials such as quartz sand, and the shell-making cycle can be shortened to a few hours. Water glass has a clear advantage in direct material and time costs.
However, post-processing and hidden costs are often underestimated. The sand-cleaning problem of the water glass process not only increases labor and energy consumption but may also increase the scrap rate due to defect repairs. The resulting sodium-containing wastewater and waste residue have increasingly higher environmental treatment costs. The silica sol process has simpler sand-cleaning and lower overall environmental costs.
When comparing water glass and silica sol, many purchasing personnel’s first reaction is often, “Which one is cheaper?”
In many OEM projects Longway has participated in, we’ve found that the real factor affecting project costs isn’t the shell material, but the entire manufacturing process.
For example, for a valve body exported to Europe, while using water glass could reduce initial casting costs by about 10% to 20%, the higher requirements for dimensional accuracy and surface quality necessitate more CNC machining, polishing, and rework processes, ultimately resulting in a higher overall manufacturing cost than using silica sol.
Conversely, for products like agricultural machinery supports and construction machinery connectors, where customers are more focused on cost control and have relatively relaxed dimensional requirements, water glass can effectively reduce the procurement budget while meeting usage requirements.
Therefore, we typically don’t simply recommend one process; instead, we analyze the product’s intended use, technical requirements, and budget to determine which solution best suits the client’s project needs.
IV. How does Longway typically help customers select processes?
After receiving the customer’s drawings, we usually do not quote immediately, but first evaluate from the following aspects:
① Product application
If the product is a pressure-bearing part, food equipment, stainless steel part or has high appearance requirements, we usually give priority to the silica sol process.
If the product is mainly used in agricultural machinery, mining equipment or engineering machinery and has moderate surface quality requirements, we will also recommend using the water glass process to help customers control costs.
②Material selection
Different materials have different adaptability to processes. For example, stainless steel products are more suitable for the silica sol process, while some carbon steel parts can use the water glass process to achieve a balance between cost and performance.
③ Subsequent processing requirements
If the part requires a lot of machining, we will comprehensively evaluate the casting accuracy and processing cost, rather than just focusing on the casting unit price.
④Annual purchasing volume
For long-term batch projects, we will also combine mold cost, production efficiency and delivery cycle to provide customers with a more competitive overall solution.
V. How does Longway help clients make more suitable process choices?
In actual projects, as an experienced investment casting supplier in China, Longway believes that every project is different. We’ve found that many clients are unsure whether to choose water glass or silica sol processes at the initial project stage.
Therefore, before providing a formal quote, we typically conduct a preliminary evaluation of the client’s drawings and offer suggestions based on the following factors:
• Product operating environment;
• Material performance requirements;
• Dimensional tolerance requirements;
• Subsequent machining requirements;
• Annual purchase quantity;
• Cost budget.
For some projects, we even provide two manufacturing options simultaneously, allowing clients to compare the differences in cost, delivery time, and quality between the different processes before deciding on the final solution.
We believe that choosing the process that truly suits the project’s needs is more important than simply selecting the lowest-priced process.