Anatomy of Woven Meshes

The threads support the stencil. The open areas allow ink passage. Familiarity with the meaning and importance of each mesh will make fabric selection easier---and consistent high-quality printing more predictable 

Mesh Count: 

The number of threads per linear inch (norminal mesh count). Screen fabrics are woven in threads per centimeter and then the number is calculated to English measurement for sale into parts of the world that don’t use the metric system 

Example: A fabric woven at 120 threads/cm equals 305 threads/inch. The figure is calculated by multiplying 120 x 2.54=304.8, this number is rounded up to 305 

Warp Threads: 
These are the threads that run along the entire length of bolt of fabric 

Weft Threads: 
These threads are woven through warp threads and run from one selvage edge to the other. 

Thread Diameter: 
This refers to the thickness of thread used to weave the fabric. Thread diameters vary widely; the thickest yarns are used to weave coarse meshes, such as 24/250, which is 24threads/inch, with a 250microns thread. High mesh count requires thinner yarns, in order to achieve workable mesh openings as the number of threads per inch increases. 305/40 has a mesh count 305 threads/inch, and a 40microns thread 

Mesh Opening: 
The mesh opening is the open area that is bounded on all four sides by woven threads. Its size is measured in microns and is represented as the width of one opening. Though all technical diagrams of mesh portray the opening as perfectly square, this is not possible when woven with a rounded thread. The weaving and finishing processes create mesh openings that are less regular than a perfect square. Mesh opening in all plain weave fabrics tend to be more consistent than those in twill weaves. The size of mesh is an important parameter when determining printability with certain inks, especially those with coarse pigments and metallic particles. 

Open Area: 
This is expressed by a percentage and simply refers to the area ”covered” by holes versus thread mass in a given area usually calculated per square meter. Two fabrics with different thread diameters can have the same mesh count, but different percentage of open area. This is important to consider when selecting a fabric for a job with a specific ink deposit requirements. 

Fabric Thickness: 
This is the measurement of a woven fabric cross-section and is used to calculate the thereotical ink volume of a screen fabric---or the cubic measurement of the mesh opening. Though it might seem logical to assume that fabric thickness the sum of two thread diameters, this is not the case. Weaving and finishing affect the total fabric thickness measurement, which is always smaller than the sum of two threads diameter. 

Tensile Strength and Yield Point: 
A screen fabric’s tensile strength is its ability to be stretched without breaking. Tensile strength is usually measured in the amount of tension required to break it. Low-elongation fabrics possess higher tensile strength than conventional fabrics. 
The yield point is that point where the polyester becomes deformed under tension, and occurs well before the breaking point. The “Plastic Deformation” causes the fabric to lose its ability to retain tension. Regardless of the tension applied to it, the fabric will not hold tension any longer. The objective in tensioning mesh is to reach an optimum level that is below the yield point. 

Mesh Color: 
Fabric color is an important criterion as it affects image reproduction and exposure time. Yellow is naturall UV Absorbent and and will provide the best stencil resolution. Exposure time is longer than those for white mesh, however, the illustration above points out the danger of using white mesh when fine details are required. White mesh reflects light, causing undercutting, sawtoothing and loss of detail, exposure time for yellow is approximately 10% less than conventionally dyed screen fabrics.

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