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The stone that is initially mined is not white but gray. Then it heats up to about 900 degrees and explodes like corn. After that, it becomes up to 13 times larger than its previous size. If we put perlite in a bag of about 30 liters, it weighs about 2 kg. Perlite tends to drain more water than vermiculite.

Perlite is used to aerate and loosen the soil and rooting cuttings and seeds. It is also used in pharmacy as a lacquer abrasive and a variety of detergents.

But what really characterizes these weird balls? We will tell you all this in the following.

سنگ های پرلیت
Perlite stone before going to the factory


Perlite In English, perlite is a white bead used in pots. These grains are actually made of volcanic rock. They are very light and hollow and also have high drainage and water permeability. They are also widely used in agriculture and greenhouses. More precisely, it is a natural mineral and, like other rocks, it is heavy at first and is composed of a series of elements!

Between 70 and 75% of it is silicon dioxide!

Between 3 and 5 percent of it is water and the rest of the elements include aluminum oxide, sodium oxide, potassium oxide, iron oxide, magnesium oxide and calcium oxide.

You can read more about perlite on Wikipedia.

پرلیت و تنفس ریشه گیاه
Perlite for aeration and soil drainage

But if you see the stone on the internet, you will notice that it is gray. So what happens to these stones that suddenly turn white and engage the minds of gardeners? Where do these white grains come from? Let’s explore this process together.

How is perlite made?

The white matter you see in potting soil is actually volcanic popcorn. As mentioned above, these rocks have some water. When exposed to high temperatures, their outer shell softens. On the other hand, the water inside them boils a lot at the same time. It evaporates and tends to find a way to escape. As soon as the surface softens, steam and water inside, come out of it very quickly and so-called burst. It then turns white.

The same thing happens inside the factory. First, perlite is crushed with a machine. Then it is exposed to temperatures of 800 to 900 degrees. The resulting material is light white balls. They also have many pores inside them. These balls are very clean and are sterilized by heat. Also, when combined with soil, they do not crumble due to soil pressure and retain their appearance.

How does it work?

Novice gardeners only pay attention to the irrigation part of the plant. They think that everything can be solved with water, but this is not the case. In addition to water, the plant also needs air. Also, without air, no creature can survive.

You might say that the plant has leaves and can breathe through it. Therefore, there is no need for all this discussion anymore. But what I want to say may surprise you. If the plant only breathes through the leaves, then why do plants whose roots are submerged by water die? Why do plants grown in wet and compacted soils dry out after a while?

The reason is clear. The root, like the leaf, needs air. Therefore, if the air does not reach it, it will die. This is something that a very experienced gardener is aware of. These white seeds cause the roots of the plant to breathe.

This is what solves the root aeration problem. This is also the reason why it is used in potting soil. On the other hand, excess water can suffocate the roots. It also drains these waters very well and passes them through to get oxygen to the roots.

In fact, the soil is compacted during irrigation and the air inside it is gradually released. These white seeds both retain air in the soil and drain excess water so as not to suffocate the roots.

How is perlite used in gardens?

Perlite has different uses in gardens. In ordinary gardens, gardeners mix it in equal proportions with peat moss, coco peat and soil. Peat moss and cocopeat store water very well. And perlite drains water very well. So we can say that they are complementary.

Some gardeners spread it on the garden surface. Gradually, when the soil is plowed, it turns upside down. Perlite is also mixed with soil and does its job. It is also very useful for growing young seeds and cuttings.

You have to be careful when using it because there are pollen and soil at the end of perlite bags. It is better to wear glasses and masks and pour them into a water bag before use so that it gets wet and the dust does not spread too much.

Application of perlite:

* Used in the agricultural industry

* Application in greenhouses and hydroponic cultivation

* Used in the construction and concrete industry

* Useful for water purification. Contaminated water is passed through a large amount of perlite and then purified and made available to the public.

One of the reasons it is so popular is its structure. This substance is such that it can store water and oxygen at the same time. Therefore, when combined with soil, it compensates for soil deficiencies and increases the growth rate of the plant.

Another reason is that it is clean. These white seeds are free of any pests and germs. Therefore, it does not rot and has a long life.

Perlite in hydroponic cultures

As we said, perlite stimulates the roots. In soilless or hydroponic beds it leads to the discharge of excess water. And does not allow the plant to sink. Perlite is usually mixed with vermiculite in a ratio of 50-50 in such greenhouses. Vermiculite solves the problem of perlite water storage. Because it is a good water saver and on the other hand, perlite removes excess water. So water is both well stored and well drained.

Types of perlite

This additive has different types that are divided into three categories depending on the size: large – medium – small

Coarse grain perlite

Coarse grain perlite has the highest water drainage rate. That is, if water is poured on it, it easily passes the water from the other side. On the other hand, the aeration power of perlite in the soil is very high and is specific to plants that need a lot of irrigation, such as orchids. It also prevents the roots from suffocating and brings air to the roots.

Medium perlite

The grains of this perlite are smaller than coarse grain perlite.

Fine-grained perlite

It is the best option for baby seeds and cuttings. You can also spread it on the garden surface. Of course, keep in mind that because it is very light, it comes on the water during irrigation and it is better to mix it with the soil so that it does not come out of the ground by water.

Is perlite organic?

This issue should be considered from two aspects. One from the perspective of chemistry and one from the perspective of agriculture.

From a chemical point of view, they are called organic things that have carbon in them. But this popcorn does not contain any carbon. It is not considered organic in terms of chemistry.

From an agricultural point of view, they are called organic products that do not use anything chemical in their production. Therefore, it is organic in terms of agriculture.


* During irrigation, it passes excess water and prevents the plant roots from suffocating.

* Due to its large cavities, it easily retains oxygen. Therefore, it causes oxygen to reach the roots of the plant.

* It does not corrode against pressure and weight and retains its appearance.

* It has a neutral pH and has no acidic or open properties.

* During climate change, less damage is done to the plant roots because it acts as insulation.

* Makes the weight of garden soil lighter.

* It can be used in soilless or hydroponic crops.

* It can be used in the construction industry.

* Economically cheap and economical.

* Has no chemical effect on soil and plants and is considered organic in terms of agriculture.

* Because it is white, when the sun shines on it, it reflects light and prevents the soil temperature from changing.

* It has a molecular structure similar to the structure of soil and is taken from nature.

Perlite in construction

* Perlite is used in wall blocks. This both lightens the buildings and insulates them from heat and sound.

* Larger grains of perlite are mixed with concrete. This makes the weight of the concrete lighter and also avoids the cost of buying cement. Because the more you do not use perlite, the more you have to use cement and sand, which costs more and makes your roof heavier.

* Perlite is sometimes used in ovens and foundries where the temperature is high. First, it is mixed with whitewashing plaster, because it prevents the plaster from cracking.

* Perlite is usually poured around water and gas pipes and the pipe is passed through them. This protects the pipes and does not damage them in summer and winter. Therefore, it does not reduce the temperature of hot water pipes.

پرلیت بلوکی مخصوص ساختمان
Perlite block for building

Perlite in steel mills

In iron and other metal workshops, bags of perlite are thrown on the surface to prevent the surface of the molten material from cooling. The bag melts and tears due to high heat. Perlites inside the bag are sprayed on the surface of the material. Due to its heat insulating properties, this material prevents the surface of the molten material from cooling.

Perlite is usually mixed with peat moss, cocopeat and garden soil and used in potting soil. Perlite has a longer lifespan than cocopeat and pithomass. It also does not allow soil to stick together when mixed with soil. Therefore, it does not allow water supply and aeration to be cut off at the root.

Perlite stores minerals and nutrients and does not allow them to be washed and removed from the culture medium during irrigation.

پرلیت در ریخته گری
تصویری از کاربرد پرلیت در ریخته گری

Where does perlite come from?

The extracted perlite is first heated to very high temperatures. This causes the amount of water in the perlite grains to evaporate quickly. So the perlite grains, like popcorn, crack and get bigger. The resulting perlite is light in weight and looks like a stone made of cotton.

Perlite is also found in some provinces of Iran, the most famous of which are the mines around Tabriz, Khorasan, Sistan and Baluchestan.

Is perlite the same as mineral pumice?

Perlite is actually a type of mineral pumice. With the difference that perlite is heated under certain conditions. But puke is brought directly to the market from the mine and sold. One of the differences between perlite and mineral pumice is its weight. Mineral pumice is heavier.

The function of perlite and mineral pumice such as vermiculite is similar in aeration. The difference between minerals and perlite is usually in the ability to absorb and store water. As we said, perlite does not have good water absorption and storage properties. That is why they use peat moss, cocopeat, and mineral pumice next to it. Therefore, in addition to ventilation, water supply also takes place. In fact, each has its own advantages. Experts also recommend using them in combination.