The technology in the manufacturing of oak barrels

The influence of the oak on the aging of wine is determined by four main factors:

Type of oak, drying, seasoning and the degree of baking during the making of the barrel. Of these factors, the burning process plays the greatest impact on the variations in the oak’s nature. Thus, it becomes the most important factor influencing the aromas of wine.

Type of oak

Experts say there are differences in the nature of oak from different forests and areas. What causes this? The main factor is soil moisture, which determines the growth rate of the tree, and hence its structure. Slower growing forests are a source of oak with a finer structure. This affects the content of tannins and vanillin as well as their attribution during the process of wine maturation in barrels. From the point of view of aromas, the age and height of the tree are also important. Very often, there are quite large differences in the structure of the tree between the top and the base. Barrel makers also take into account the type and width of the annual circles, as well as the radial rays from the center of the trunk to the tree bark, all of which gives them information about the amount of vanillin and tannin.

Terroir and oak species influence tannin content. Normally the French oak has more tannins. The type of American oak, which is used exclusively for wine barrels, is Quercus alba, the largest woods being found in the state of Missouri. The European oak used by most of the barrel makers on both sides of the Atlantic is represented by two species - Quercus robur and Quercus petraea. Quercus petraea reaches the European border with Russia, with Quercus robur being prevalent in Russia. Still, most of the Quercus robur oak is used to make barrels for alcoholic drinks.
For some time, the production of wine barrels originating in Russian oak has been growing, as Russia has the largest oak woods in the world and the oak price is lower. Russia and the United States and France are ranked by area. In the ratings of tree area, the United States and France follow Russia.

Southern “Stara Planina” is a relatively large source of Quercus petraea. According to the research, the oak in our lands is close to the French oak and it is characterized with a higher content of tannins than the American oak. From the big caster companies, the American World Cooperage was the first to promote the qualities of our oak as it began to work on а project to promote the so-called Balkan oak.

Drying and seasoning

The tree begins to dry as soon as it is cut. It could lie on the ground where it was cut down, a few months before being taken to a workshop. This is considered the beginning of the drying. At first chopping, about half of the oak is moisture, but after three months it decreases by 20%. Under natural conditions oak is usually dried to between 14 and 16% moisture content. Logs are hygroscopic, humidity increases in winter and decreases in the summer.

Seasoning is the next phase. As the oak dries, the boards change, volatile substances evaporate, others are oxidized, and there is a certain microbiological activity that causes the destruction of some substances and the creation of others. Again, these changes are influenced by the conditions in which the oak is stored. In a humid environment, mold and various types of fungi will develop on the surface. Some of them will penetrate into the oak and can cause dissolving and decay. Oak, which is stored outdoors and exposed to rain, may lose some of its valuable components irreversibly. It is believed that longer seasoning mitigates the character of the barrel made by this oak.


The traditional method is related to the use of open fire from logs, the barrel maker is relying on the aromas that are released from the burned arcs to judge the desired degree of baking.

More advanced methods are used, such as the barrel temperature and burn time being monitored by computers.

During baking, when the barrel is heated to a certain temperature, different flavors are formed, as the heat penetrating the boards releases components that are at different depths in the wood. The surface temperature of the boards, the time and degree of firing are influenced by the length of the seasons.

Research has confirmed that tannins are most sensitive to heat and are easily dissolved. With subsequent temperature increase, sugars contained in the wood begin to caramelize, so the aroma of oak is transformed into a sweet spice flavor. Lignin decomposes to produce a vanilla aroma. At higher temperatures and degrees of baking the rich aromas of almond, chocolate, coffee and so-called "smoky" flavors are achieved.

Oak and acacia barrels

The main material, oak, supplied from the Varna, Veliko Tarnovo and Preslav regions and acacia, after initial treatment, are allowed to dry for a period of 18 to 30 months. The rings used are galvanized or black / ordinary / depending on customer request. The following thermal processing standards are used: LT, MT, MT +, HT.

Production and repair of:

Barrels with volumes 5l, 10l, 20l, 30l, 50l, 100l, 150l, 200l, 225l, 250l, 300l, 350l, 400l, 450l, 500l, 550l, 600l, and 1t.c.

Casts, butter pistols, rakia barrels. A wide range of pots are also available.

Our workshop has a license for the manufacturing of Bulgarian, French and American barrels.

The company offers oak arch-boards for barrels.