Common Problems and Solutions for Putty Powder
Release Time:
2020-07-17
Source:
Powdering issue with water-resistant putty
1. The product does not cake or cause powder fallout.
Cause: Improper technical formulation; the putty lacks film-forming agents.
Solution: Increase the proportion of non-fiber-based adhesive in the putty.
Such as PVA polyvinyl alcohol powder, redispersible latex powder, other modified starch-based adhesive powders, and sodium-based bentonite.
The product doesn’t lose powder at first, but it does after a while.
Cause: The putty lacks film-forming agents and contains excessive starch-based adhesives; over time, it absorbs moisture from the air, leading to chalking.
Solution: Adjust the proportion of binder added to the putty, such as PVA polyvinyl alcohol powder or redispersible latex powder.
The primary cause of powder loss is an unreasonable formulation of the product’s technical specifications.
There are relatively few reasons for unreasonable construction practices.
For substrates that are excessively dry and absorb water rapidly, pre-spraying with water or applying a latex primer is essential; otherwise, powdering will occur (provided the water-resistant putty itself is of good quality).
How to Prevent Hollow Sounds
The base surface must be thoroughly cleaned and free of oil stains and loose dirt.
Water-resistant putty shall not be applied over 821 putty (or over a previous coat of putty that has severely chalked).
Water-resistant putty shall not be applied to substrates with lower strength than the water-resistant putty (such as polystyrene boards and rock wool).
The base layer shall be solid and free from movement, impact, or vibration.
The application thickness for each coat of water-resistant putty should not exceed 1.5 mm, and the total thickness should not exceed 2.5 mm.
It is best to smooth each coat of putty after application, which helps to densify the substrate and reduce its water absorption.
If chalking has occurred, the putty must be coated with adhesive before construction can proceed.
How should the application be carried out when the substrate is uneven and the total putty thickness exceeds 2.5 mm?
— First apply a primer coat using putty adhesive (108 glue or 791 glue) mixed with cement (P.O 32.5 or higher) at a weight ratio of 1:2 for leveling and surface preparation.
— Apply water-resistant putty adhesive after drying
The primary cause of hollow-sounding areas is improper construction techniques.
There are few reasons for the poor quality of water-resistant putty.
When water-resistant putty lacks crack-resistant additives, it is prone to delamination.
Yellowing Issue in Water-Resistant Putty
Main reason:
Gray calcium powder tends to yellow over time.
Different regions, or even different raw-material mines within the same region, can result in variations; for example, some grades of lime putty from Zhejiang and Guangxi exhibit a yellowish tint.
Hebei-produced quicklime (light calcium oxide) should not yellow.
The environment is humid after putty application, or the substrate is not completely dry.
Some additives at the base layer react with the putty.
Water-resistant putty has poor workability.
Lack of raw materials that improve processability (cellulose, wood fiber)
Fillers such as hydrated lime powder have insufficient fineness (more than 90% pass through a 325-mesh sieve).
Low binder content (PVA powder, modified starch)
The base layer is excessively dry and absorbs a large amount of water.
Water-resistant putty has poor water resistance.
Fillers such as hydrated lime powder and white cement are used in small proportions (with more than 90% passing a 325-mesh sieve).
Low binder content (PVA powder, modified starch)
The substrate is excessively dry and absorbs a large amount of water, resulting in insufficient powdering of the putty.
The putty has not been troweled smooth.
