What Is Bolting Cloth?

Bolting cloth is a fine-mesh woven fabric — traditionally silk and now predominantly nylon, polyester, or stainless steel — used for precision sieving and classification of powders in vibratory screeners, test sieves, and production sifters, especially at mesh sizes where woven wire becomes too fragile. The term "bolting" originates from flour milling, where the process of separating bran from flour through a fine cloth has been called "bolting" for centuries.

Modern bolting cloth is precision-woven on specialized looms that maintain tight aperture tolerances. Nylon (polyamide) and polyester are the dominant materials for food and pharmaceutical sieving, while stainless steel bolting cloth serves chemical and high-temperature applications. The fabric is available in aperture sizes from approximately 5 microns to 4,000 microns, though its primary advantage over wire mesh is most apparent below 200 microns where metal wire becomes extremely thin and fragile.

Bolting Cloth Material Comparison

Why Bolting Cloth Matters in Vibratory Screening

Bolting cloth plays an essential role in industries where fine powder handling, gentle material treatment, and anti-blinding performance are priorities:

• Superior blinding resistance at fine mesh — The smooth, round fiber cross-section of nylon and polyester releases particles more readily than rough woven stainless steel wire, drastically reducing blinding when screening fine powders.
• Durability at fine apertures — Below 100 microns, stainless steel wire becomes extremely thin and tears easily. Nylon and polyester fibers at the same aperture size are more flexible and resist tearing, extending screen life in fine sieving applications.
• Food and pharmaceutical compliance — Nylon and polyester bolting cloth meet FDA food contact requirements and are the standard media for flour sifting, sugar grading, pharmaceutical classification, and cosmetic ingredient screening.
• Cost efficiency for consumable screens — In high-volume sifting operations, the lower cost of nylon or polyester bolting cloth compared to stainless steel mesh significantly reduces ongoing operating costs.

Bolting cloth screens are used on vibratory separators from Sweco, Kason, Midwestern Industries, Russell Finex, and ScreenerKing for food, pharmaceutical, chemical, and cosmetic applications.

Related Glossary Terms

• Woven Wire Cloth — Metal wire screen media for vibratory screeners
• Test Sieve — Standardized sieve for laboratory particle analysis
• Mesh Size — Number of openings per linear inch
• Blinding — Clogging of screen openings
• FDA Compliant — Meeting food and drug contact regulations
• Screen Cloth / Screen Media — General term for screening surfaces

Bolting Cloth FAQs

What is bolting cloth used for in vibratory screening?

Bolting cloth is used for fine and ultra-fine particle separation in vibratory screeners, typically in the range of 20 microns to 1,000 microns. It is the preferred screen media for sifting flour, pharmaceutical powders, cosmetic ingredients, and fine chemical powders where precision classification and gentle handling are required.

What is the difference between bolting cloth and woven wire mesh?

Bolting cloth is woven from synthetic fibers (nylon, polyester) while woven wire mesh is woven from metal wire. Bolting cloth is lighter, more flexible, and resists blinding better at fine openings. Wire mesh is stronger, more temperature-resistant, and more chemically resistant.

Is bolting cloth FDA approved for food processing?

Nylon and polyester bolting cloth are widely used in FDA-regulated food processing environments and comply with FDA 21 CFR for food contact. Nylon bolting cloth is the standard sifting medium in commercial flour milling and bakery ingredient screening. Always verify that the specific grade meets your regulatory requirements.