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Furnace plaster: how and with what to plaster the oven, mortar recipes

Stucco Furnace

With the advent of the era of total gasification, traditional stoves began to be perceived by us as a relic of the past. There were practically no special innovations in decoration, but in vain! The furnace is a reliable source of heat, not suffering from power outages and energy prices (gas, diesel fuel, pellets). Today, a reassessment of values ​​has taken place, the services of stove-makers are again in demand, the almost forgotten secrets of the furnish are being restored. If you decide to tidy up the old stove or plaster a new one, the question of the correct selection of the building mixture is inevitable, because the requirements for finishing materials are quite high – the plaster will be heated repeatedly afterwards. It is important that the base is environmentally friendly – various toxic compounds may be released during heating, which is unacceptable, in addition, the plaster must have elasticity and good thermal conductivity. We will consider various options for the composition of the plaster, so that the question “how to plaster the stove” found the only correct answer.

Content

  • The purpose of plastering the furnace
  • How to plaster an oven
  • Let’s get ready for the rules
  • Solution application process
  • Which plaster is better to use
  • The purpose of plastering the furnace

    Firstly, the plaster gives the stove a neat appearance, decorates the interior of the room. Secondly, plastering enhances the strength and tightness of the masonry. Indeed, over time, due to temperature changes in the masonry, cracks form through which smoke can enter the room, which negatively affects not only the interior (smoked walls, curtains and furniture), and most importantly – it is dangerous for health.

    The cost of numerous heat-resistant materials presented on the shelves of building supermarkets is much higher than the traditionally used mixtures for the plastering of clay-based furnaces. You can plaster the furnace with a clay-sand mortar with the addition of cement or lime or a lime-gypsum mortar. Clay-based solutions are most commonly used. It is possible to plaster the brickwork only after it has completely hardened to eliminate shrinkage (after about a month). The percentage of components in the clay-sand solution is not the same. It all depends on the fat content of clay. If the fat content is high, 4 parts of sand will be needed for 1 part clay. In order to increase the strength of the plaster, additional components are often added to the solution: fiberglass or asbestos.

    How to plaster an oven

    Prepared surface

    The stove prepared for plastering: defects are repaired, the surface is cleaned, the seams between the bricks are embroidered

    Let’s get ready for the rules

    First of all, you should properly prepare the surface: clean from dirt, dust, residues of the old solution. In order to improve the adhesion of the mortar to the brickwork, an additional clearing of the joints to a depth of 5 to 10 mm is recommended. It is recommended that the nails be hammered into the seams (40-50 mm long) in increments of no more than 15 cm, so that they protrude about a quarter of the length. It is advisable to treat the surface with a primer specially designed for such purposes. In order to create additional roughness (for bond strength), a fiberglass mesh should be used. It is attached to the masonry using a liquid layer of mortar. Only hot walls are plastered..

    Stucco Furnace

    Furnace plastering is carried out in stages, usually several layers of mortar are applied, each of which is given time to completely dry

    Solution application process

    The solution is applied in stages (in layers). Before applying the plaster, be sure to moisten the masonry with water. The first layer of plaster must be made liquid, creamy consistency. After the first layer has hardened, you can apply a second layer, up to 1 cm thick, after the second layer has set, you can begin to level the surface. After the solution has set a little, you can wipe the surface. Before grouting it is necessary to moisten the plaster with water, then wipe all irregularities with a grater in a circular motion. If cracks are visible after drying, expand them, moisten with water, fill with a solution and, after drying, wipe.

    Which plaster is better to use

    Furnace plaster has special requirements. The composition of the building mixture for plastering the furnace is significantly different from conventional cement-sand mortars for plastering the walls of houses. This is due to the fact that the masonry of the furnace, when heated, has the ability to expand, and for reliable bonding it is extremely important that the plaster is flexible. In addition, in order for the stove to warm the room well and quickly, the stove plaster must have good thermal conductivity. In order to impart such properties, various components are added to the composition of the solutions: clay, fireclay, asbestos, fiberglass, salt. Both simple clay and complex solutions are used, which you can prepare with your own hands or buy ready-made mixtures in the store. Examples of common mixtures will be considered in table 1.

    The composition of mortar mixtures

    Table 1. The composition of the mortar mix for plastering the furnace

    Depending on the fat content of the clay, the ratio of the components of the solution may vary. The clay is fatter, the more sand will be required. The order of mixing the solutions is approximately the same – the first thing is to mix the dry components, adding the mixture to a solution of lime or clay. For added strength, 200 g of salt can be added to a bucket of clay-sand mortar.

    Consider recipes for commonly used compositions for plaster: part of clay, part of lime paste, one tenth of asbestos and two parts of sand are laid at the same time. The mixture should be thoroughly mixed, and gradually adding water, bring to the desired consistency.

    Another recipe for durable plaster (the only drawback of the mixture is the need for quick use, because an hour after preparation the mixture will be unsuitable): for two parts of sand, you need to take one part of clay and cement (grade 400 or 500). First, you need to knead thick dough from water, clay and sand, then add cement and asbestos to the composition, add water and mix thoroughly. The density of the solution should be sour cream-like consistency.

    Any composition necessarily includes an astringent aggregate and water. The binder may be a single component or mixture (e.g., cement and lime). If you decide to use a high-strength gypsum-based mixture, consider an important feature: the mixture sets very quickly (within 6 minutes). After half an hour, such a mixture is already unsuitable for use..

    By choosing one of the above recipes for the composition of the mixture for plaster, or using a purchased mixture, monitor the quality of the solution. A properly prepared solution should be easily and evenly applied to the masonry, there should also be no problems with smoothing. The proportions are important – the viscosity is regulated by adding water, we do not exceed the norm of sand – the plasticity of the solution will suffer.

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