Water Resistance of Gypsum

Ordinary gypsum has no water resistance.

If you place a gypsum board and leave it under running water overnight, it will develop holes.

This is because gypsum has relatively high solubility, dissolving about 0.2 g in 100 g of water.
Therefore, gypsum products cannot be used in places where water is present, such as outdoor walls.

Conversely, the solubility of gypsum can also lead to its diverse applications.

Examples of utilizing gypsum’s solubility include coagulating tofu, manufacturing ceramic mold materials, improving soil, and coagulating alginate impression materials.

Methods to Increase Water Resistance

• 1. Apply a water repellent or paint. ( Use a water repellent or paint to create a barrier that prevents dissolution when exposed to water.)
• 2. Make it a resin composite material. (Combine gypsum with acrylic or melamine resin.)
• 3. Apply substances that react with calcium to form insoluble compounds. (Potassium soaps, carboxylates)

Simple Methods to Impart Water Resistance

• 1. Water-soluble acrylic paint can increase water resistance just by applying it, and mixing it with gypsum can create a composite material.
  Try using 5-10% of the gypsum weight.
  However, the material must be completely dry to be effective.
• 2. Repeatedly applying and wiping off potassium soap can create insoluble calcium soap, improving water resistance.
• 3. Purchase water-resistant products.
  Our industrial gypsum products, RC-150 and RCL-100, have significantly high water resistance as they are.

＊Note : None of these methods provide complete water resistance.
However, discovering a cost-effective and efficient method could expand the potential applications of gypsum.