Alabaster: What is it? How to breed? Where to apply?

Alabaster is one of the oldest building materials, known to masters for more than 5 thousand years. And it is still in demand, despite the appearance of numerous dry building mixtures and the stricter requirements of the construction industry. Why?

Gypsum = alabaster?

Non-construction people sometimes get confused in terms: one thinks that gypsum and alabaster are synonyms, just everyone calls it as they used to, others say that alabaster is the best and highest quality variety of gypsum.

Some even believe that alabaster is a stone from which statues are sculpted, and when ground it is used for finishing work, so it is harder and whiter than gypsum.

So what is alabaster?

This is truly a "subspecies" of gypsum. Like building gypsum, it is obtained from a natural mineral - gypsum stone, both of them are calcium sulfate, only the first is two-water (CaSO4 • 2H2O), and the alabaster is semi-water (CaSO4 • 0 , 5H2O) .

The mineral is ground and then burned at a temperature of about 180 ° C.

The grinding of alabaster is thinner than that of building gypsum, and therefore this material has less ductility, but greater hardness.

Also, its unique feature is the drying time - alabaster mortar sets in an average of 5 minutes, that is, much faster than other building mixtures.

These properties narrow the range of application of alabaster to construction and finishing works, while gypsum can be used in many industries, including medicine, jewelry, casting, art, etc.

Characteristics and types of alabaster

The main averaged characteristics of alabaster are presented in the table below:

Compressive strength 4.0 MPa
Bending strength 2.0 MPa
Binder grade G5 - G6 for building mixtures, as well as for the production of drywall, gypsum boards and gvl

g13 – g25 for the production of elements of high strength
Water consumption (in terms of 1 kg of dry mix, by snip) 0.65-0.70 liters
Setting time 5-30 minutes from start to finish
Fire resistance heating to 700 ° without damage
Color White, pearl gray, yellowish, light green, light pink (the color depends on the characteristics of the deposit and, according to experts, does not affect the strength properties of the finished surface)

Since one of the main features of the mixture is a quick set of strength, three types of alabaster are distinguished by hardening speed:

View Index Setting time, min. Setting time, min.
Quick hardening A 2 fifteen
Normally hardening B 6 thirty
Slow hardening IN 20 No standard

Benefits of Alabaster

  • Quickly and smoothly! Thanks to the quick setting, the surface can be leveled in literally minutes, and after an hour, and if you take it with a margin, it is ready for further processing.
  • Alabaster solution has high adhesion and perfectly fits on almost any prepared surface
  • In the frozen form, the alabaster has good strength characteristics and. To this day, preserved elements of palaces and temples that are more than 5 thousand years old, and they are in excellent condition. Drying, the material does not shrink and is resistant to cracking
  • Hardened alabaster absorbs noise , so it can be used as an auxiliary material for sound insulation. 6 hours of exposure to open fire - this is how much it can withstand alabaster without significant deformation. It does not burn itself and prevents the spread of flame.
  • As part of the material there are no chemical additives , it is environmentally friendly and can be safely used in bedrooms, children's rooms, etc.
  • Democratic compared to similar dry mortar mixes similar in cost.

Alabaster use

Due to the characteristics of the material, the range of application of alabaster in construction is wide: it is relevant for the production of drywall, is in demand by professional builders, and is also often used by private traders for minor repairs.

  1. Correction of cosmetic defects of walls , ceilings and GKL / GVL surfaces. Alabaster mixture is traditionally used to eliminate a variety of chips, chisels, cracks, etc.
  2. Preparation of surfaces for finishing Alabaster mixture is excellent for puttying walls and partitions in rooms with normal humidity, it is used to prepare surfaces for wallpapers of all types, as well as decorative plaster. Some builders use alabaster even in bathrooms, for tiles, but in this case it is necessary that the material is completely hidden by the lining and not in contact with water. This principle is also true for the kitchen, because the alabaster absorbs wet fumes.
  3. Electrical work Alabaster is the joy of an electrician, a convenient material that allows you to quickly fix the cable in the wall without the risk that it will move when the mixture dries. In addition, many use it when installing a socket, as even with a rough pulling of the plug from the socket, the structure, thanks to the hardness of the alabaster, is guaranteed to remain in the wall, which sometimes more expensive and modern dry mixes cannot provide.
  4. Interior decoration . When decorating rooms with stucco molding, a specific problem often arises: cast gypsum elements have a solid weight and therefore must be firmly fixed to the base. This is especially true for ceilings. And alabaster in this case is an ideal option. He will come to the rescue for masking and sealing up small defects of stucco molding and is indispensable for restoration work.

Getting Started

When working with alabaster, half the success depends on the quality of preparation, namely, on the selection of containers and tools.
To facilitate the process, consider the following principles.

  • There is no metal container right away ! Alabaster tightly clings to the iron walls, which means loss of material, inconvenience and damaged container. Plastic dishes are better suited, but rubber is still the most comfortable option: the solution does not stick to the springy walls, and after the work is completed, the dried-up residues are easily shaken out, for this it is enough to compress the mold several times and then turn it over. In addition, if desired, in construction stores you can purchase special buckets for working with plaster.
  • There is no immediately leftovers container ! A dried solution speeds up the hardening of a new closed portion.
  • As for the spatula, modern tools from plastic or rubber are very convenient, the mixture does not stick to them. But a classic steel spatula is better, a new one is better: according to the observations of some masters, rust speeds up the setting of an already quick-hardening mortar

For small volumes

Small portions of alabaster are conveniently closed in nylon buckets or compact rubber containers . Often, builders use halves of ordinary children's balls of suitable diameter.

A spatula is optimal for stirring "small doses" of alabaster mixture.

For large volumes

Plastic or rubber bucket line with a solid piece of cellophane, tight and without holes, tack the "tails" to the edges of the container so that the polyethylene does not move during stirring; after use, the film is simply removed from the bucket and discarded.

It is convenient to mix the solution with a construction mixer, and in its absence - with a drill with a nozzle.

Mixing and working with the solution

Here it is important to answer three questions: in what proportion to mix, how exactly to mix and what nuances should be considered when mixing?

Actually, the proportions depend on the purposes for which the solution is planned to be applied. SNiP recommends the following ratios:

The amount of dry mix Amount of water
For mixing alabaster plaster and grout 1 kg 0.65 liters
For mounting and repair mortar 1 kg 0.5 l
For liquid grout 1 kg 1 liter

In order not to ruin the material and get a quality solution, strictly adhere to technology .

  • Remember that the mixture is added to the water, but by no means the other way around !
  • The powder needs to be poured gradually , like flour into a pancake dough, and thoroughly mixed until the mass is uniform.
  • The correct filler solution has the consistency of mousse or yogurt.
  • If the solution begins to harden, and you did not have time to spend it or do what you planned, just throw it away without trying to “reanimate” by adding water . With alabaster, the principle “died so died” is 200% true, the grasped solution is no longer suitable.
  • When applying the solution, make a note that when drying, the material increases slightly in volume.

Tips from the Masters:

  1. Theory and SniPy - this, of course, is good, but in practice, alas, a dry mixture can behave differently, it all depends on the brand and even the batch. Therefore, before shutting the entire desired volume, conduct a test with 100 grams of material.

  2. Use cold water to shutter . .

  3. When mixing the solution, it’s definitely worth it strive for uniformity . However, overdoing is also fraught: there is an opinion that too long and thorough mixing, especially with a mixer, violates the structure of alabaster, as a result of which it loses strength.

How to prolong the viability of alabaster solution?

Beginning masters, as well as private traders without experience and construction skill, when working with alabaster often ask the question - is it possible to slow down the hardening of the solution a little.

And there really are such ways. Some of them are quite scientific, some relate to "folk" methods, which, nevertheless, have shown themselves well in practice.

Method 1: Bone Glue.

A good old tool, approved by more than one generation of builders. When mixing, add any glue on a bone basis, whether it is poorly diluted paint or carpentry. The main thing is the dosage: 2% of the total weight of the mixture.

Method 2: Citric Acid

The recipe is as follows: for 0.5 cups of alabaster, take 4-5 grains of citric acid and toss when kneading in cold water. However, the masters note that, with apparent simplicity, the method is not universal, t. k. the amount of acid must be selected for a specific alabaster mixture, that is, tests and experiments are required.

Method 3. PVA glue

Here the builders are divided into two camps. Some say that 3% PVA per mass of the mixture gives an excellent result, that is, they prolong the viability of the solution by several times and do not affect its strength in the future. Others object to them - they say that the film that PVA forms on the surface when dried can block the evaporation of water, so that crystallization and coarsening of crystals of sodium sulfate hydrate is likely, and this leads to a deterioration in strength characteristics.

How to choose and where to buy?

It would seem that alabaster is a simple mixture, without chemistry, without plasticizers, take the first packet of any brand and go ahead, because it is difficult to spoil the material. However, there are still nuances in the choice.

  1. Since alabaster is extremely moisture-sensitive, it should be stored in dry rooms . So it is advisable to purchase the mixture in stores, rather than in markets where the tightness of containers often leaves much to be desired, and especially not in open air areas
  2. Carefully check the integrity of the packaging , as at the slightest violation of it, there is a chance that the material has partially or completely lost its properties.
  3. No matter how simple the alabaster mixture is, it’s worth choosing not only by price, but also by manufacturer : large producers are a priority, because, thanks to the established and regulated production, they are ready to ensure quality stability , while for noname brands the quality can “dance” strongly from batch to batch.
  4. Give preference to brands whose packaging shows the proportions for mixing their mixture , because, despite the norms of SNiP, recommendations may vary.

Buy Samaragips brand alabaster


Samara, Russia
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