Liquid stone: stone plaster for interior and exterior use

Recommendation points

• Properties and varieties of material
• Self-preparation of plaster mortar
• Types of suitable substrates and their preparation
• Application and alignment procedure

Continuing the theme of unusual finishing materials, we will introduce our readers to stone plaster. It can be used both on the facade or plinth, and indoors, while providing a high variability of appearance and ease of application.

Properties and varieties of material

Stone plaster or liquid stone is a special type of finishing materials with high aesthetic value. There are several varieties, at the same time they are all crushed natural minerals mixed with a polymer binder, which is usually a translucent polyurethane or acrylic adhesive.

As a mineral filler, as a rule, granite or quartz is used, less often marble, crushed and sifted through to form grains ranging in size from 0.5 mm to 2-3 mm. In order for the particles of a natural mineral to form a dense structure and have high-quality adhesion with a binder, cover the surface with a uniform layer, in the production process they are thoroughly washed, achieving complete removal of the dust-like fraction, and then mixed with atmospheric curing plastic compounds by vibration method – in this form, the product comes ready-made to the end consumer.

This material is quite rare and it should be noted that in most cases of using such finishing options, the mixture is prepared by the craftsmen on their own. And this is not surprising: on sale you can find both stone chips and a binder, and with a completely democratic cost. In the end, the result is definitely worth the effort: the finish surface takes on the appearance of a stone powder with a high-quality appearance, excellent resistance to moisture and mechanical stress, does not lose its aesthetic properties over time.

To give additional decorative value, a mixture of stone chips with a polymer binder is colored. In this case, two methods of tinting are possible: coloring the filler with the expectation of settling particles of a finely dispersed dye in the pores of the mineral, or coloring the finished mixture, as a result of which the necessary tone is given to the binder in order to give additional color depth.

Self-preparation of plaster mortar

In reality, a mixture of stone and polymer glue, ready for application, is quite rare. But the availability of starting materials well contributes to the self-preparation of the composition, often it is this circumstance that makes it possible to provide a unique type of finish.

Finely crushed granite, shungite, quartz, sometimes even jadeite and tourmaline are chosen as a mineral filler, which provides a high decorative value – it all depends on the individual preferences of the customer. There are few requirements for the quality of raw materials: the absence of fine dust and a uniform particle size. Quite often, mineral chips are sieved and washed independently before use, which is not difficult, but this way you can ensure high-quality adhesion of the filler with the binder, as well as eliminate glue clouding, as a result, guaranteeing a bright, pronounced color of the natural mineral and providing an effective play of light on the edges of the chipped particles.

The fraction of the crushed mineral is selected based on individual preferences, but it must be remembered that grains larger than 2 mm form an excessively rough surface and, depending on the quality of the binder, may have an increased likelihood of shedding. At the same time, too small a crumb size (less than 0.5 mm) contributes to the formation of a monolithic and practically smooth crust on the surface, in which the specific qualities of the natural mineral are practically indistinguishable. In general, the choice of rock chips and particle size presents an incredibly vast field for creativity..

As for the binder adhesive, there are not many variations in this regard. Polyurethane glue is best suited, the amount of which is determined at the rate of 3-5% of the mass of stone chips, more accurately the consumption is determined by the instructions. The adhesive can be one-component, ready-to-use, or formulations that require a hardener to be used. All that is needed for cooking is to pour the required portion of glue into a bucket with filler and mix thoroughly with a mixer, achieving complete enveloping of stone particles. In the process of preparing and using the mixture, it is very important to prevent the ingress of water, from it the composition sets almost instantly.

For interior work, a binder based on acrylic and its copolymers is best suited. Its main advantage is its water base, which prevents the release of volatile solvents during the application process. Acrylic adhesive is also characterized by a long pot life of the mixture: about an hour versus 15–20 minutes for polyurethane. That is why acrylates are ideal for creating complex plaster mosaic compositions..

Types of suitable substrates and their preparation

Stone chips in the solidified form have some elasticity, and therefore the tendency of the base to moderate cracking does not play a decisive role. The strength of the roughing coat and the quality of adhesion are much more important.

When applying stone chips to a preparatory layer of gypsum or cement plaster, the surface must be cleaned of crumbling dust and sand, then thoroughly impregnated with a universal primer, which contains quartz flour. If there are irregularities on the surface intended for finishing that exceed 3-4 sizes of the crumb fraction per m², additional leveling is required to reduce consumption.

Stone plaster can also be applied to concrete, for example when finishing a plinth. It is only important to remove residual efflorescence and treat the concrete surface with a metal brush, at the same time making sure that there is no deck grease or oil stains. Before coating with crumb, it is enough to treat the surface once with a primer such as “Betonkontakt” and dry well.

There are no obstacles for finishing with liquid stone structures sheathed with sheet materials. The surface can be represented by gypsum sheets or chipboards, in both cases it is possible to achieve high quality adhesion of the material to the base. It is only necessary to carry out preliminary processing with glue, which is used to prepare the solution, diluted to 1/3 of the initial concentration. The surface before finishing must have time to dry “to touch”.

Application and alignment procedure

Stone plaster is applied in sections of 1-1.5 m² using a rectangular trowel. Initially, a small amount of the mixture is pressed tightly against the prepared surface and slightly stretched on the sides until a layer of the required thickness is formed, which, as a rule, is 2-3 sizes of the filler fraction. In the same way, the composition is applied to an adjacent area, the mixture must be stretched towards the already coated part, achieving the complete disappearance of the joint and ensuring the uniformity of the coating.

When a small area is completely covered with crumb, a final leveling is performed. At the same time, the trowel must be kept strictly parallel to the wall and make circular movements with it with slight pressure. If this results in streaks and streaks, they can be crushed with light cotton after the glue has set. The leveled surface must be carefully examined for the presence of foreign inclusions and local irregularities. If everything is in order, we prepare a new portion of the mixture and continue finishing the neighboring area.

Due to the polymer binder, stone plaster is hydrophobic with a layer thickness of 3-4 mm. However, small pores on the surface tend to accumulate dust, which can degrade the appearance of the finish over time. Indoors, this problem is solved by periodic cleaning with a vacuum cleaner, while the external finish can be covered with polyurethane transparent varnish after the plaster has dried..