What is Water Glass (Sodium Silicate) Used for in Mold Making?

Water glass — also known as sodium silicate — might sound like a fancy term, but it’s an essential material used in mold making and casting. Whether you’re working with sand molds or creating precision cores, water glass plays a key role in holding everything together, quite literally.

But why is it called "water glass"? And what makes it so useful in mold making? Let’s dive into what it is, how it’s used, and why mold makers and artists rely on it for consistent results.

What is Water Glass?

Water glass is the common name for sodium silicate, a chemical compound made from sodium oxide (Na₂O) and silica (SiO₂). Its chemical formula is Na₂SiO₃. It appears as a viscous, clear to slightly cloudy liquid, and it's available in multiple forms — liquid, powder, or pre-mixed solutions.

This versatile material is water-soluble and becomes a glassy solid when dried or cured — hence the name water glass.

How is Water Glass Used in Mold Making?

Water glass is prized in the casting and mold-making industry for its adhesive and bonding properties, especially when combined with carbon dioxide. Below are the primary ways it's used:

1. Binder in Sand Casting

One of the practical uses for sodium silicate is as a binder in sand casting. It’s mixed with silica sand to create molds, and then CO₂ gas is passed through to harden the mold quickly. This results in strong, durable molds that can hold their shape under high temperatures.

2. Investment Casting

In investment casting, water glass helps build ceramic shell molds. It improves mold strength, ensures dimensional accuracy, and gives a better surface finish — making it a solid choice for fine, intricate castings.

3. Core Making

Water glass is also used for core making, where it binds sand to form the hollow interior spaces of complex metal castings. These cores need to be precise and strong — something water glass handles with ease.

4. Fireproof and Refractory Mold Applications

Due to its heat resistance, water glass is ideal for making molds that must withstand high temperatures. Whether you’re working with molten metal or glass, sodium silicate molds retain their shape and integrity during the casting process.

Benefits of Using Water Glass in Mold Making

• Strong bonding agent: Offers solid adhesion with mold materials.
• Eco-friendly: A better alternative to harmful organic binders.
• Cost-effective: Affordable for large-scale casting operations.
• Quick setting: Cures rapidly when exposed to CO₂ gas.
• Reduces deformation: Maintains mold shape during casting.

Applications Beyond Mold Making

While sodium silicate is mainly known for its mold-making use, its properties make it valuable in other industries too. In fact, water glass works as an excellent adhesive in many settings:

• Fireproofing materials
• Ceramic manufacturing
• Adhesives for porous materials
• Textile and wood preservation

How to Use Water Glass in Mold Making (Step-by-Step)

1. Mix sodium silicate with dry, clean sand.
2. Shape your mold or core.
3. Cure it by passing CO₂ gas through the mold to harden.
4. Allow the mold to air dry or bake if necessary.
5. Handle with care and follow all safety precautions.

Precautions and Safety Guidelines

Working with sodium silicate is generally safe, but it’s important to follow these safety tips:

• Always wear gloves and eye protection.
• Avoid direct skin or eye contact.
• Work in a well-ventilated area, especially during CO₂ curing.
• Store in a sealed container to prevent contamination or drying.

Where to Buy Water Glass for Casting?

Looking to get started with water glass? ArtMolds Sodium Silicate is available in different quantities to suit hobbyists, educators, and professionals alike. Whether you’re making a one-off art piece or mass-producing castings, our products are designed to meet your mold-making needs.

Explore our sodium silicate product line here and get in touch for usage tips or complete silicone mold making using sodium silicate kits.

Conclusion

Water glass (sodium silicate) may be simple in form, but it's a powerful ally in the mold-making world. From sand casting and core making to fireproof molds and investment casting, its versatility is unmatched.

If you’re in the mold-making or casting business, it’s time to take advantage of what water glass has to offer. Whether you're an artist, educator, or industrial manufacturer, ArtMolds has the tools and materials to help you create with confidence.

ED MCCORMICK

Edmund McCormick is the founder of Cape Crystal Brands and EnvironMolds LLC. He is the author of several non-fiction “How-to” books, past publisher of the ArtMolds Journal Magazine, editor of Beginner's Guide to Hydrocolloids, and author of six eBook recipe books available for download on this site. He resides in Far Hill, NJ and lives and breathes his art and food blogs as both writer and editor. You can follow him on Twitter and Linkedin.