What Is Gypsum Retarder And The Right Way To Use It

What is Gypsum Retarder and the right way to use it

Gypsum retarder is mainly used for plastering gypsum, bonding gypsum, gypsum putty, gypsum products, and other gypsum building materials, mainly to reduce the setting speed of gypsum. The disadvantages of traditional gypsum retarders, such as short time and large strength loss, have been solved successfully, and the strength and construction efficiency of gypsum have been improved. Here is how to use a gypsum retarder.

At present, the commonly used retarders are mainly as follows:

  1. Inorganic salt retarders, such as gypsum retarders include quicklime, slaked lime, calcium carbonate, sodium carbonate, borax, sodium hexametaphosphate, sodium polyphosphate, alkaline phosphate, ammonium phosphate, etc.
  2. Organic acid retarders, which are mainly organic acids, soluble salts, proteins, polyols, and sugars.
  3. Organic macromolecular retarders, which are mainly organic polymers, such as polyvinyl alcohol, methylcellulose ether, bone glue, polyacrylic acid salt, etc.
  4. Commercial retarder, which is usually made of a variety of retarders, to give full play to the advantages of a variety of single retarders.

What is the right way to use a gypsum retarder?

  1. 0.03% – 0.5% in hemihydrate gypsum.
  2. With the increase of the content of the gypsum retarder, the setting time increases.
  3. With the increase in air temperature, the amount of gypsum retarder should be increased properly.
  4. Due to the variety and performance of gypsum, the effect of gypsum retarder may be different, and the dosage shall be determined before use.
  5. When it is used for plastering gypsum, gypsum retarder and 0.5% of cement can effectively prolong the retarding time.
    What should be paid attention to when using gypsum retarder

The function of the gypsum retarder :

To slow the setting speed of gypsum. This is because the gypsum building material is light, not easy to deform, the chemical property is stable after hardening, and will not crack when drying, so the application of gypsum in daily life is very extensive, the only disadvantage is that the setting speed is fast, so gypsum retarder came into being, which can control the setting time of gypsum well. The following is an introduction to the precautions for using gypsum retarder.
What are the precautions for the use of gypsum retarder?

  1. When in use, the high-efficiency gypsum retarder and gypsum powder are uniformly mixed or the high-efficiency retarder is dissolved in water, and then gypsum powder is added. Application scope and adding amount: the adding amount of plastering gypsum, bonding gypsum, caulking gypsum, gypsum caulking agent and gypsum putty is 0.1% – 0.3%, and the adding amount of prefabricated gypsum component, gypsum block, and gypsum board is 0.05% – 0.15%.
  2. Due to the different sintering quality of gypsum powder in different places, the standard and consistency used are different. Before using high-efficiency gypsum retarder, it is necessary to do strict tests to determine the best adding amount.


Gypsum retarder is a necessary construction chemical in many applications. We can use gypsum retarder together with cellulose ether such as HPMC,MHEC to make many kinds of products.

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