Textile Notes related to fiber, yarn, fabric knowledge, spinning, weaving, processing, projects, knitting, Indian Traditional Textiles and denim manufacturing
“ I want to know how to calculate max EPI and PPI of the given count. For Example, if we take 50s pv warp X 150 D 100% polyester weft, what will the max EPI and PPI if we weave it for plain, 2/2 twill,and satin.”
Here Mr. Ashenhurst can rescue us. The following method is based on his book “Textile Calculation and Structure of Fabrics”. Here the assumption is there is only one count of thread in both warp and weft. If there are two different counts of warp and wefts, threads per inch should be found out for both of them and then suitably adjusted.
The General formula to calculate Maximum EPI and PPI for a Given count of Warp and Weft
Now in a plain weave in a repeat there are 2 threads and 2 intersections. For 2/2 Twill in one repeat of 4 threads there will be 4 threads and 2 intersections.
Also as a rule please remember that 40s count yarn diameter is 1/165 of an inch.
To convert it to the yarn diameter of 50s warp we use the following formula
Which means for 50s PV Warp the diameter will be
Thus the Maximum Threads per inch for a plain weave will be 184 as this will be the diameter of the Yarn.
For 2/2 Twill be they will be ( From the Formula above)
Which means x will be equal to 122 threads per inch
Similarly for Satin weave one can find out the maximum ends and picks per inch
Please remember however that this is theoretical construct. Actual threads per inch are generally less than that.
To Calculate the Cotton Equivalent of 150 D, We use the formulaà count= 5315/denier, Which means it is equal to 35.43 or 35 count.
The Diameter for 35 count yarn will be ( Using the formula above) = 154.34 th of an inch
Then you can use the same equation to calculate the Maximum EPI and PPI
In these examples there is no allowance for bending, shrinkage or compression, the threads should be reduced or increased proportionately in case the fabric is subjected to bending, shrinkage or compression.
The Sindhi Taropa denotes the interlacing stich embroidery-- the basic structure which is first built up with the use of long thread stitches into the surface and entire structure being built up thereafter by looping these threads, the overall effect produced is geometrical; floral patterns or figures, whatever is worked out through this type of stitch become-somewhat stylized. Practically the stitch is used as a means of achieving only an impression of the figure or motif which is aimed at.
How to Calculate the Weight of Fabric from Count, EPI, PPI and Width
One very common practical question in fabric sourcing is:
“If I know the yarn count, fabric width, ends per inch and picks per inch, can I estimate how much warp and weft yarn is required for 100 metres of fabric?”
The answer is yes. We can estimate it quite reasonably, especially for cotton woven fabrics, provided we understand the assumptions behind the calculation.
This calculation is useful for merchandisers, fabric buyers, converters, traders and small fabric suppliers because yarn prices change frequently. If the yarn price increases, the fabric price should also move logically. Without a basic calculation, it becomes difficult to judge whether the quoted fabric price is reasonable or inflated.
To calculate the approximate fabric weight, we need the following details:
Warp yarn count
Weft yarn count
Ends per inch, also called EPI or reed
Picks per inch, also called PPI
Fabric width in inches
Warp crimp percentage
Weft crimp percentage
For a quick practical estimate, we may assume:
Parameter
Assumed Value
Warp crimp
10%
Weft crimp
3%
1 metre
1.0936 yards
1 pound
453.59 grams
Cotton count basis
840 yards per hank
Practical Note: Warp crimp and weft crimp are not fixed values. They change with weave, yarn type, fabric density, finishing and shrinkage. The values of 10% and 3% are only working assumptions.
The Basic Cotton Count Formula
In the English cotton count system:
\( \text{Cotton Count} = \frac{\text{Length in yards}}{840 \times \text{Weight in pounds}} \)
Therefore:
\( \text{Weight in pounds} = \frac{\text{Length in yards}}{\text{Count} \times 840} \)
This is the foundation of the fabric weight calculation.
Warp Weight per Metre
The warp weight per running metre can be calculated as:
\( \text{Warp weight per metre in grams} =
\frac{\text{EPI} \times \text{Width in inches} \times \text{Warp crimp factor}}
{\text{Warp count} \times 840}
\times 1.0936 \times 453.59 \)
\( \boxed{11.25 \text{ kg of yarn is required for 100 metres of fabric}} \)
How to Calculate GSM from This
Many people confuse grams per metre with GSM.
Grams per metre tells us the weight of one running metre of fabric.
GSM means grams per square metre.
\( \text{GSM} =
\frac{\text{Weight per running metre in grams}}
{\text{Width in metres}} \)
For 47 inches width:
\( 47 \text{ inches} = 1.1938 \text{ metres} \)
Therefore:
\( \text{GSM} =
\frac{112.52}{1.1938} \)
\( \text{GSM} = 94.25 \)
So this fabric is approximately:
\( \boxed{94 \text{ GSM}} \)
Common Confusion: A 47-inch fabric and a 60-inch fabric may have different weight per running metre even if their GSM is similar. Running metre weight depends on width; GSM is normalized to one square metre.
Suggested Visual 3: Difference between grams per running metre and GSM.
This gives fabric weight in grams per running metre.
For 100 metres:
\( \text{Weight for 100 metres} =
\text{Fabric weight per metre} \times 100 \)
Important Practical Notes
1. This is an estimate, not the final invoice weight
The formula gives the theoretical yarn weight in the fabric. In real production, the final weight may change due to sizing, desizing, bleaching, dyeing, finishing, shrinkage and moisture regain.
2. Crimp must be adjusted for fabric type
A plain fabric, twill fabric, satin fabric, dobby fabric and heavy canvas will not have the same crimp. Warp crimp and weft crimp should ideally be measured from the actual sample.
3. Width matters
The formula uses fabric width in inches. If the width increases from 47 inches to 60 inches, the yarn requirement increases proportionately.
4. Count system matters
This formula is for cotton count or English count. It should not be directly used for denier, tex or metric count without conversion.
5. Add process wastage separately
If you are calculating yarn purchase requirement, add suitable wastage.
The difference is small, but the corrected version is technically cleaner because it uses more accurate conversion constants.
Final Rule of Thumb
To estimate woven cotton fabric weight:
Fabric weight depends mainly on four things: yarn count, EPI, PPI and width.
Finer yarn means lower weight.
Higher EPI or PPI means higher weight.
Greater width means higher running-metre weight.
Higher crimp means more yarn consumption.
Once this logic is understood, fabric costing becomes much more transparent.
General Disclaimer
The calculations and explanations in this article are intended for educational and practical estimation purposes. Actual fabric weight may vary depending on yarn quality, weave structure, crimp, sizing, finishing, moisture content, shrinkage and testing conditions. For commercial costing, production planning or quality approval, calculations should be verified with actual sample testing and mill-specific data.
This (http://www.ajrakhprinting.co.in) is an amazing website giving in amazing details the process of Ajrak Printing. Owned by Ranamal Khatri, the master craftman, this website can be used as an authentic one to study the process.I met Mr. Ranamal Khatri during my visit to Jodhpur. This site will give you a glimpse of the joy of watching Ajrak Made. This gives in details the process, the receipe, the comparison with the earlier process and a mouth-watering view of the products. To top it all, he has put in the process video wherein one can have a look at the process in action. And last but not the least, a look at the artisans working in his workshop and who have made it possible is given. Here are some pictures from the website:
Receipe
Video of the Process
Ajrak Saris
Artisans
Awards won by Him
There is a very good M.Des. Research done by B. Sinduja. You can access it here
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The following is a brief description of the chemical dyes used in handblock printing in India:
Pigment dyes
Pigment colors are mixed with kerosene and a binder. The mixed color can be stored for a few days. The motif is printed directly on white or light-colored ground with a variety of pigment colors. Pigment colors are widely popular today because the process is simple, the mixed colors can be stored for a period of time, subtle nuances of colors are possible, and new shades evolve with the mixing of two or three colors. Also the colors are visible as one prints and do not change after processing. Colors can be tested before printing by merely applying it onto the fabric. The pigment color is made up of tiny particles, which do not dissolve entirely and hence are deposited on the cloth surface while rapid dyes and indigo sols penetrate the cloth.
Rapid fast Colors
In this process, the ground color and the color in the design are printed on white and/or light-colored grounds in one step. The dyes once mixed for printing have to be used the same day. Standard colors are black, red, orange, brown and mustard. Color variation is somewhat difficult and while printing it is not possible to gauge the quality or depth of color.
Discharge Dyes
These dyes are used if you need to print onto a dark background. Medium to dark grounds are dyed on fabric with specially prepared dyestuff . The printing colors then used on the fabric contain a chemical that interacts with the dye. This interaction simultaneously bleaches the color from the dyed ground and prints the desired color on its place. Areas can also be discharged and left white. The primary advantage of this process is that vivid and bright colors along with white can be printed on top of medium and dark grounds.
Napthol
These are two sets of chemicals which upon reaction produce a third chemical essentially colorful in nature. Fabric is dyed in one and later printed with the other. The chemical reaction produces a third color. However, the biggest drawback of this process is that there are just a few chemicals available which produce colors upon reaction.
Almost all the reactive dyes are built on a similar structure (Remazol Dye from Hoechst is the exception). This structure consists of (1) a chromophore (the color-bearing group), (2) a reactive group (usually a heterocyclic carbon-nitrogen ring system), and (3) a "leaving group" which is part of the carbon-nitrogen group which is generally a halogen compound (chlorine family).
Influence of Dye characteristics in reactive dyeing:
The major dye variables that affect reactive dyeing are dye chemistry, substantivity,Reactivity and solubility.
Dye chemistry:
Reactive dye has a wide variety in terms of their chemical structure. The two most important component of a reactive dye are the chromophore and the reactive group. The characteristics governed by the chromophore are color gamut, light fastness, chlorine / bleach fastness, solubility, affinity and diffusion.
The dye characteristics governed by reactive group are reactivity, dye-fiber bond stability, and efficiency of reaction with the fiber and affinity. Dyeing conditions, especially the alkali requirements and temperature as well as the use of salt also depends upon the type of reactive group.
Substantivity:
The affinity of dye for a given substrate ( textile material) is called substantivity
Substantivity more depends upon chromophore as compared to reactive system. A high substantivity may results:
• Lower dye solubility.
• High primary exhaustion.
• A high reaction rate.
• Lower diffusion coeffecient.
A low sensitivity of dyes to the variation in the processing conditions such as time, temperature, pH, material to liquor ratio may results:
• Less diffusion.
• Less migration and levelness.
• More difficult to the removal of unfixed dyes.
Substantivity is also the best measure of the ability of a dye to cover dead cotton or immature cotton fibers. Covering power is best when the substantivity is either high or very low. An increase in the dye substantivity may be affected by:
• Lower concentration of dyes.
• Higher concentration of electrolyte.
• Lower temperature.
• Higher pH upto 11.
• Lower liquor to material ratio (M:L)
Reactivity:
High dye reactivity entails a lower dyeing time and lower efficiency of fixation. To improve the efficiency of fixation by reducing dye reactivity requires a longer dyeing time and therefore less effective than an increase in substativity. Also there is wide range of temperature and pH over which the dye can be applied. Altering the pH or temperature, two dyes of intricsically different reactivity may be made to react at a similar rate can modify reactivity of dye.
Solubility:
Dyes of better solubility can diffuse easily and rapidly into the fibers, resulting in better migration and leveling. Increasing the temperature, adding urea and decreasing the use of electrolyte may affect on increase in dye solubility.
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People have always been interested in the connection between clothing and physical well-being.Comfort has its physiological, physical-chemical and psychological components. Major components in case of textiles are Warmth, Absorbing capacity and humidity, General comfort , Cloth convenience , Skin perception , Weight and Softness. Out of these major part of comfort is directly related to the body temperature. Thus any clothing can be measured on comfort by the fact that how well it can regulate the temperature of the body. Sweating is the most effective way the human body has of cooling down. How well can a clothing provide comfort depends upon (among other factors) how well it can handle sweating.
The most effective cooling is achieved by sweat evaporating directly on the skin. Thus any clothing that behaves closest to the skin is comfortablee. The ability of a textile to transport perspiration in the form of vapour through itself and out to the exterior is generally referred to as its breathability. It is incorrect to use the terms breathability (or resistance to water vapour) and air permeability interchangeably, because low air permeability does not in itself result in lower breathability. The best example of this is modern wind- and waterproof membranes, which allow very little air to permeate in from outside (windproof), but still allow evaporated perspiration to pass through from the inside.
Fiber characteristics influence breathability the most. However contrary to popular belief,synthetic fibers are not always bad in terms of comfort. If textiles made from synthetic fibres were properly designed, they could not only offer the same heat and moisture management qualities as natural fibres but even exceed them.For example in in double faced clothings, layers of natural and synthetic fibres were combined, yet kept separate. The synthetic fibres of the "double face material" were next to the skin and conducted perspiration quickly and efficiently away from the body and into the outer cotton layer. In combination, the two materials were far more comfortable than cotton, because of the drier feeling on the skin."
There are some interesting developments in getting comfort characteristcs of fabrics they include a gradual variation in the fineness of the fibres and yarns from the inner surface of the textile to the outer surface. It improves moisture management; because the resulting narrowing of the capillaries (denier gradient) means that the moisture can be transported away from the skin really effectively. Other measeures include integrating electrical and electronic components such as heating or cooling elements. The latest battery technology and innovative methods of processing and wiring.
