We often encounter the problem of foaming during wall decoration. Is it a construction problem or a quality problem of putty? Today we will analyze the truth about putty bubbles.

Blistering on the mortar wall

【Phenomenon】: Dense bubbles form when the putty is scraped up. However, there are no deep air holes in the base surface.
【Formation principle】: The mortar surface foams, often because the mortar surface is too rough. When the putty is scraped, the air cannot be effectively discharged, thereby lifting the putty paste and forming air bubbles;
【Solution】: Use a roller to roll a liquid interface agent to facilitate exhaust. Then scrape putty, the air bubbles will be greatly reduced.

Blistering on the base surface

Putty foaming, the first reason is the base surface:
【Phenomenon】: The bubbles appearing on the base surface not only bulge very high. And after piercing, the inside is also very deep.
【Formation principle】: The base surface of the batch putty is the cement surface of the cast-in-place slab. The surface has dense air holes left after demoulding. When scraping on such a base surface. The air hole is sealed by the putty paste, and the air in the air hole is compressed to form accumulated potential energy. Then when the scraper leaves the air hole. The putty paste is bounced up by the sealed and compressed air in the air hole, forming air bubbles. The greater the viscosity of the putty and the finer the putty, the stronger the bubbles.
【Solution】: Use a low-viscosity thick putty to scrape the first time. Or scrape the first pass with gypsum that can be quickly molded and does not rebound, and it can be solved.

Scraping the second layer of putty and foaming

【Formation principle】: In such a situation, it is often that the first putty has not eliminated the air bubbles. When scraping the second layer of putty, I habitually use a spatula to level it, breaking the air bubbles in the first layer. Returning to the first situation, the same principle (see the first item above) continues to generate a new bubble on an air hole.
【Solution】: At this time, don’t shovel the first air hole. Continue to scrape thickly with leveling putty or plaster. to cover up the air bubbles.

Scraping putty foaming

【Phenomenon】: The formula of the bottom putty is not suitable, and there are pinholes on the surface after molding. Scrape the putty on the eye of the needle and foam. (The principle is the same as the first one above)
【Solution】: Replace the leveling putty.

Non-“gas” foaming

The above three bubbles are all related to “gas”, and the following is not a problem of gas——
【Phenomenon】: This bubble is a bubble formed by the separation of the surface layer and the inner layer, just like the bubbles of the skin that has been scalded by boiling water.
[Formation principle]: Old walls, whitewashed walls, or interior wall putty with insufficient quality are not resistant to water or have surface pulverization. The intrusion of moisture that cannot bear the second putty is dissolved and loses its structural strength. Coupled with the damage caused by the scraping of the second putty scraper and blistering.
【Solution】: Seal the first putty with a sealing wall (it must be removed if it is serious). Then add water-retaining agent and adhesive (environmental glue can also be used) to the second putty to solve the problem.

Other reasons

Sometimes, even with a fine finish putty for the base layer, blistering occurs.
【Solution】: Use a well-filled low-viscosity leveling putty for the first pass.