Views: 48 Author: Site Editor Publish Time: 2025-09-22 Origin: Site
Cracking and hollowing are two of the most common and tricky issues in mortar work. They don’t just ruin wall finishes—they can lead to big problems like water leaks and material peeling, hurting overall project quality and how long the structure lasts. As a building materials technician, I want to share how one often-misunderstood additive—starch ether—makes a huge difference in fixing these flaws, going way beyond its usual label as just a thickener.
Most pros think starch ether only makes mortar thicker, but its core superpower is great water retention. This is the key to solving both cracking and hollowing right at the source.
Fast moisture loss is the top cause of mortar cracks. On absorbent bases (like aerated concrete blocks) or in hot, dry weather, the base layer soaks up mortar moisture like a sponge. This cuts short the cement’s chemical reaction (called hydration), leaving the mortar weak and prone to shrinking and cracking as it dries.
Starch ether forms a steady water-holding network in the mortar mix. This network slows down moisture evaporation and absorption by the base layer, giving cement enough time and water to fully and evenly complete its hydration. With full hydration, the mortar gains all its strength, and the risk of cracking drops a lot.
Hollowing (air gaps between mortar and the base layer) usually comes from poor bonding. A major cause is mortar bleeding or separating: before the mix hardens, weak water retention or the mix’s own weight makes water split from solids, creating a gap between the mortar and base.
Starch ether fixes this in two simple ways:
Its strong water retention stops bleeding, keeping the mortar mix smooth and consistent from application to drying.
It improves the mortar’s anti-slump and thixotropic properties (meaning it’s smooth to spread but stays put once set), so the mix sticks firmly to vertical walls without sliding down. This keeps the mortar in tight contact with the base layer, creating the best conditions for mechanical and chemical bonding—and getting rid of hollowing completely.
To get the best results from starch ether, follow these easy guidelines:
Check compatibility: Make sure your starch ether works well with your type of cement to avoid mix issues.
Test the amount: Starch ether delivers big benefits at ultra-low doses (0.02%–0.05% of the total dry powder weight). Quick on-site tests will help you find the perfect amount, making it a very cost-effective solution.
Using starch ether isn’t just about making mortar easier to apply. Its water-holding and thickening properties add a solid layer of protection for the mortar’s long-term strength and durability. For teams looking to cut down on rework and deliver high-quality builds, it’s a small change that makes a massive difference.
