Bursa Silk / Bursa Silk Thread

Bursa Silk / Bursa Silk Yarn is a textile raw material unique to Bursa Province in Türkiye, derived from the silkworm cocoon and protected under geographical indication. This yarn is obtained from silkworms fed on the leaves of morus trees that grow in Bursa’s mineral-rich soils and mild humid climate. For centuries it has been a fundamental element of the region’s weaving and textile tradition. Bursa Silk is produced through the processing of cocoons from silkworms raised according to specific quality and production standards; it is distinguished by its whiteness brightness and drawability. The feeding and cocoon-spinning stages occurring within the boundaries of Bursa Province define the product’s geographical character while the yarn-drawing process may take place outside these boundaries.

Bursa Silk / Bursa Silk Yarn (Türk Patent)

History

Bursa Silk / Bursa Silk Yarn has historically been linked to the production of silkworm eggs and cocoons in Bursa Province. For centuries Bursa served as a center where silk fabrics and velvet were woven on handlooms and traded widely. The oldest recorded evidence of silkworm rearing for cocoon production is a 1587 document recording the sale of a mulberry orchard. Bursa’s central role in the silk trade began to develop in the second half of the 14th century and became firmly established in the 15th century. Evliya Çelebi’s travel notes highlight velvet textiles among Bursa’s silk products. In the 16th century Bursa textiles held commercial value not only across the Ottoman territories but also in European cities such as Florence Venice and Genoa as well as distant regions like Iran and China. During the Ottoman period it was common to refer to these fabrics as “Bursa Cloth”.

Bursa Silk / Bursa Silk Yarn (Bursa Metropolitan Municipality)

When the Ottoman-Iran wars weakened silk cocoon trade from Iran local cocoon production in Bursa began to increase. By the mid-17th century a class of artisans known as “mancınıkçı” silk yarn producers emerged and by the end of the century numerous workshops employing primarily female workers had been established. The expansion of sericulture boosted raw silk exports to Europe and reinforced the Ottoman territories’ role as a key raw material source. Silk production in Bursa provided long-term employment and led to the establishment of factories by families such as İpeker with products shipped via Gemlik Port to various cities. Structures such as Kozahan and İpekhan functioned for many years as commercial and trading centers.

The role of mulberry trees in the development of cocoon and yarn production in Bursa is crucial. Bursa offers suitable conditions for the growth of these trees due to its geological features and abundant underground water sources which reduce the rate of hardening associated with aging. Bursa Silk / Bursa Silk Yarn is produced through the cocoon-spinning of silkworm eggs raised on mulberry leaves native to Bursa followed by the processing of these cocoons into yarn.

Geographical Features and Influences

The most important factor determining the quality of Bursa Silk / Bursa Silk Yarn is Bursa’s geographical structure. The leaves of mulberry trees growing on the slopes of Uludağ in mineral-rich volcanic soils are used to feed silkworms. Because the hardening of these trees due to aging is slow and minimal the resulting cocoons exhibit high quality. Bursa’s mild and humid climate plays a decisive role in silkworm development and cocoon quality.

Seed (Silkworm Egg) Characteristics

The yield and quality of cocoons obtained from silkworms depend on the characteristics of the eggs used in the feeding process. In the production of Bursa Silk / Bursa Silk Yarn hybrid silkworm eggs polihibrits typically imported from the Far East are used. These eggs are a hybrid resulting from the crossbreeding of Japanese European and Chinese strains. The type of imported eggs may vary over time and new disease-resistant strains may be incorporated into production as they are developed. The defining feature of Bursa Silk / Bursa Silk Yarn lies in the feeding and cocoon-spinning processes of the larvae hatched from these eggs. The role of mulberry trees native to the Bursa region is critical during these stages. After being fed on these mulberry leaves silkworms produce cocoons.

Bursa Silk / Bursa Silk Yarn (Bursa Metropolitan Municipality)

Cocoon Characteristics

The silkworm is a domesticated insect species belonging to the Bombyx mori of the Bombycidae family within the order Lepidoptera. It undergoes four life stages: egg larva pupa and adult moth. The larva hatched from the egg passes through five instars and four molting periods during its approximately 25-30 day development phase during which it consumes large quantities of mulberry leaves. Larvae fed on mulberry leaves from trees grown in Bursa begin spinning cocoons using a secretion from their mouths after sufficient nutrition and molting. The cocoon-spinning process typically lasts two to four days and concludes with the completion of the yarn structure.

Silkworm eggs are stored in cold storage for one year before development begins under suitable environmental conditions through hatching (inficar). The inficar process is a critical stage that affects larval development and ultimately the yield and quality of cocoons. The approximately 25-30 day period from egg hatching to cocoon spinning constitutes the feeding and rearing phase of silkworm larvae.

The quality of cocoons including their silk content yarn drawability and general characteristics is closely related to Bursa’s climatic conditions. Feeding and rearing activities are carried out primarily in spring and autumn under mild humid weather. Disinfection of feeding areas during this period is essential to reduce disease risk. Additionally silkworms require clean air and must be kept away from enclosed stagnant environments. Temperature and humidity must remain constant during feeding; ideal conditions are approximately 23-26°C and 70-75% humidity. Bursa’s natural climate provides these conditions. Cocoons produced under these conditions typically yield white and lustrous yarn.

After completing the feeding process silkworms are suspended on racks for cocoon spinning. Racks are usually made from annual plants such as mustard asparagus fern oak branches pınar and black poplar and are discarded after use. Alternatively plastic racks may be used due to their durability ease of disinfection labor advantages and their ability to increase silk yield while reducing the incidence of double cocoons.

Production Process

The production of Bursa Silk Yarn consists of several stages: acquisition of silkworm eggs feeding the eggs raising them on racks cocoon spinning and finally yarn drawing. Production begins with imported eggs being fed on mulberry leaves native to Bursa. After feeding and suspension silkworms begin spinning cocoons. Approximately 8-10 days after suspension cocoons are collected. At this stage weak and stained cocoons are first removed to prevent damage to healthy ones. The loose fibers on the surface of the cocoons known as “cocoon fluff” are cleaned.

Cocoon spinning is completed when the silkworm transitions from the larval stage to the pupal stage inside the cocoon. This stage lasts six to ten days depending on temperature. In silk yarn production this stage is halted before the pupa transforms into a moth through a process called “cocoon boiling”. The cocoons are then dried and the yarn-drawing process begins. The silk spun by the silkworm is in its raw form and cannot be used directly; therefore it must be processed into yarn.

Bursa Silk / Bursa Silk Yarn (Bursa Metropolitan Municipality)

In yarn drawing filaments from a specific number of cocoons are combined and twisted to produce yarn of the desired thickness. Today two main systems are widely used. In the French system filaments from two groups of cocoons are twisted twice and drawn through two separate porcelain guides before being wound onto bobbins. In the Italian system filaments from a single group of cocoons are twisted on themselves in filament form and wound onto bobbins.

Bursa Silk / Bursa Silk Yarn (Bursa Metropolitan Municipality)

During cocoon boiling and yarn drawing the end of the silk filament must be located. This is done by cleaning the tangled fibers on the cocoon surface known as “whip ends”. If these whip ends are not removed the quality of the drawing process deteriorates. The search for the filament end can be performed manually or mechanically. Cocoons are softened in water at 90–95°C. In manual methods the ends are found using sticks or brushes. In mechanical methods semi-automatic or fully automatic machines are used. In these machines a rotating brush moves over the cocoons in the trough collecting the filament ends. After approximately 20–25 rotations the brush is raised and the collected filaments are cleaned by a worker.

Bursa Silk / Bursa Silk Yarn (Bursa Metropolitan Municipality)

Cocoons with located ends are placed in the drawing bath. The thickness of the yarn to be drawn denier is adjusted according to the machine or number of cocoons. Filaments from the cocoons pass through a porcelain guide. This guide consists of two nested tubes and in modern machines is integrated with a yarn catcher. The silk exiting the guide is twisted and wound onto a bobbin. After passing through the first and second reels the silk is twisted and transferred to the third reel and distributor guide. This twisting process is called “taveleta twist”. In manual systems the end of a newly located cocoon is tied by hand to the existing yarn. In machine systems the cocoon is connected mechanically by a catcher.

Bursa Silk / Bursa Silk Yarn (Bursa Metropolitan Municipality)

The twisting process ensures that the silk filaments remain tightly bound together and that water from the drawing bath is removed from the fibers. Without twisting loose filaments may break reducing yarn and fabric quality. Excess water not removed may cause residue buildup and hard surfaces. The main types of twist used in silk are “chambon” and “taveleta” twists. The chambon twist is formed by wrapping two separate silk yarns several times around each other and winding them crosswise onto bobbins and is typically used in systems operated by hand and foot power. In modern machines the taveleta twist is preferred; in this method the yarn is twisted around its own axis.

In the final stage of the drawing process silk passes through the distributor guide and is wound onto bobbins or reels that move back and forth. The circumference of the bobbins is 148-150 cm in direct drawing machines and 60-65 cm in other machines. In simpler machines the bobbin circumference may vary and materials such as wood aluminum or hard plastic may be used. Ultimately the silk drawing process is completed when the cocoon fibers pass through various stages and are wound onto bobbins.

Bursa Silk / Bursa Silk Yarn (Bursa Metropolitan Municipality)

Geographical Boundaries and Production Conditions

Bursa Silk / Bursa Silk Yarn derives its characteristics from the soil structure climatic conditions and quality of mulberry trees in Bursa. Therefore the feeding and cocoon-spinning stages of the silkworm must occur strictly within the boundaries of Bursa Province. However the subsequent yarn-drawing process which carries a low risk of degradation may be carried out outside these geographical boundaries.

Bursa Silk / Bursa Silk Yarn (Bursa Metropolitan Municipality)

Monitoring and Registration

Bursa Silk / Bursa Silk Yarn was registered as a geographical indication on 29 March 2019 under number 425. The application was submitted by the Bursa Metropolitan Municipality and the usage and monitoring processes are conducted under municipal coordination. The monitoring body consists of representatives from Kozabirlik Bursa Chamber of Commerce and Bursa Chamber of Commerce and Industry. Monitoring is carried out at least once annually and reports are submitted to the Turkish Patent and Trademark Office.

Bursa Silk / Bursa Silk Yarn (Bursa Metropolitan Municipality)

The geographical indication label must be used on product packaging or an appropriate section together with the phrase “Bursa Silk” or “Bursa Silk Yarn” and the geographical indication emblem. The monitoring process covers not only the yarn itself but also fabrics textiles and even imported similar products to ensure they are correctly labeled in the market.

Usage and Notification Obligations

Producers using the name Bursa Silk / Bursa Silk Yarn are required to notify the Bursa Metropolitan Municipality of such use. Notification is also required when this silk is used in new products; this is not a licensing process but a mere informational requirement.

Bursa Silk / Bursa Silk Yarn (generated by artificial intelligence)