Gypsum has many uses in the construction industry. The preparation method of gypsum mortar has many variations according to its application in construction, so that the smallest changes in the amount of water, mixing method, ratio of water and gypsum, water temperature, etc. is effective on the structure and quality of the obtained mortar. Types of plaster mortars are divided based on quick setting and slow setting, the amount of concentration and even how to use it. One of the types of gypsum mortar is the anhydrous mortar. This mortar is one of the hardest mortars and the way it is made is different from other mortars. In this article, we have given a complete explanation about plaster of Paris and anhydrous plaster and how to make them. Stay with us until the end of this article to learn more about and the way to make them.

plaster of Paris and anhydrous plaster

What is anhydrous gypsum and plaster of Paris?

Plaster of Paris is a mortar that is made with whitening plaster or micronized plaster in the usual way and It is used for whitening walls. One of the natural features of gypsum is its quick setting. Ordinary plaster mortar is usually after 8 minutes, that’s why the plaster worker has no enough time to implement a smooth and uniform surface. To solve this problem, anhydrous plaster was made.

The anhydrous plaster is a long-lasting mortar. It retains its malleability and plasticity most of the time. Therefore, plaster has enough time to polish the surface. The anhydrous plaster is applied as a thin layer with a thickness of one millimeter at the end of the work. The mechanical resistance of plaster is low and the probability of its falling due to impact is high. Soft plaster is used to make anhydrous plaster.

How to make anhydrous plaster?

To make anhydrous plaster, you need ordinary plaster, water and a clean Istanbul piece. In the following, we have mentioned the steps of making anhydrous plaster in order:

First, ordinary plaster should be sifted through a fine sieve.

Fill the Istanbul container halfway with clean water and slowly add the sifted plaster to the water and stir the mixture slowly at the same time.

This part is the most important step in the preparation of plaster. At this stage, after all the plaster has been poured into the Istanbul, stir the mixture continuously for about 10 minutes.

At this stage, plaster of Paris is destroyed and anhydrous plaster is formed.

To prepare anhydrous plaster, you must pay attention to the ratio of water and plaster. About 0.7 to 0.8 liters of water is used per kilogram of sifted gypsum. The amount of water should be equal to 70% to 80% of plaster.

How to prepare plaster of Paris

To prepare plaster of Paris, you need a clean container, ordinary plaster and water. The way to make plaster of Paris is as follows:

In the first step, pour half of the container with clean water.

Then add the plaster to the water.

Then let the plaster soak for 1 to 2 minutes and then mix the mixture by hand or mixer until it is uniformed.

After that, you should use mortar for about 5 to 7 minutes so that it does not harden.

Note that the amount of water should be 70% of the weight of plaster.

 

plaster of Paris and anhydrous plaster

  • Advantages of the plaster of Paris

    The advantages of the plaster of Paris are:

    Creating a smooth and uniform surface

    High flexibility

    being quick

    Soundproof

    High resistance to fire

    Fair price

    Abundance and availability

Making easy and simple

What is the difference between anhydrous plaster and plaster of Paris?

As we said before, anhydrous plaster and plaster of Paris are both whitening and ordinary plaster, and the difference between them is in the way of making their mortar. The difference between these two kinds of plaster is as follows:

In the preparation of anhydrous plaster, after pouring plaster powder in water, we immediately stir the mixture to prevent the formation of plaster crystals because the formation of crystals causes the plaster to harden. But for the preparation of plaster of Paris, we give some time for water absorption by plaster grains. To prepare the plaster, the plaster mortar should be rubbed for about ten minutes. Whenever the gypsum mortar starts to harden, it can be turned into a paste by stirring and adding water. Adding water reduces the mechanical strength of plaster

What is skim coat?

One of the stages of finishing is skimming coat. After the wall is finished, the surface of the wall should be smoothed. For this purpose, they use plaster and soil mortar and cover the surface of the wall with a layer of plaster and soil. After fixing the defects of the wall and creating a smooth and uniform surface, it is time for whitewashing, which is done by whitewash plaster. After the wall is whitewashed and before the plaster is completely dry, a thin layer of anhydrous plaster is drawn on the wall, this work is called skim coat. By skimming coat, all the pores are filled and the surface becomes completely smooth and uniform. Note that the thickness of the plaster layer should be 1 mm. If it is thicker, the plaster will crack or form a flaky.

Advantages of anhydrous plaster

anhydrous plaster is widely used in the construction industry due to its advantages and characteristics. The advantages of anhydrous plaster are:

High flexibility

Long-lasting plaster

Creating a smooth and uniform surface

sound Insulation

High resistance to fire

The price is right

Abundance and availability

How to make easy and simple

Disadvantages of anhydrous plaster

Along with the advantages of anhydrous plaster, there are also disadvantages. The disadvantages of anhydrous plaster are as follows:

Low resistance to moisture
It has low mechanical resistance
High resistance to metal corrosion

Bolour Gatch Saveh is the best collection for buying all kinds of plaster

In this article, we wanted to fully introduce you to the concept of anhydrous plaster and plaster of Paris and teach you how to make them. As we mentioned in this article, the use of anhydrous plaster, due to the time it takes and the slowness of this mortar, has made the work of plasterers very easy to create a smooth and uniform wall. An important condition for making a quality mortar is to use high-quality plaster. Bolour Gatch Saveh Factory is considered as one of the largest gypsum producers in Iran. You can buy high-quality plaster online at a reasonable price through the website. For more information and to make an order, contact our colleagues through the numbers listed on the site.