**What is Lap dip?
**Lab dip refers to a small sample of fabric or textile material that has been dyed in a laboratory setting to match a specific color. It is a crucial part of the color matching process in the textile industry.

Calculation of the dyeing recipe is done by the dyeing master. The whole work process is done in lap dip. Lab dip is a process by which buyers supplied swatch is matched with the percentage of the varying dye in the laboratory. Lab dip plays an important role in shade matching & and detaching the characteristics of the dyes and chemicals that are to be used in the large scale of production. So this is an important task before bulk production. This article just for beginners who are entering into **dyeing production**. Dyeing recipe calculation formula will help to them.

**Dyeing Recipe Calculation Formula **

**Recipe Calculation Formula: **

**Required Dye = {Shade percentage (%) x Weight of the fabric in gram (gm)} / Percentage (%) of Stock solution.**

Or,

**Required solution = Fw*Sp / Cs**

Where,

Fw = weight of the fabric, yarn, or fiber

Sp = shade percentage

Cs = concentration of stock solution

For calculating the required amount of auxiliaries (chemicals) the formula is as below:

Required amount of solution (mls) = (Gram/liquor required x Weight of substrate x Liquor ratio ) / {10 x concentration (%) of stock solution} (cc).

For the addition of auxiliaries in solids form such as salt, soda the formula is :

Salt in gram/ liquor = {Required amount (%) x Sample weight x Liquor Ratio} / 1000

The conversion formula from percentage to gram/ liquor is as below :

Gram/liquor = Required amount (%) x 10 .

If alkali concentration is given then the formula to calculate this in gram/liquor is as follows:

Required amount of solution (mls) = (Gram/liquor required x Weight of substrate x Liquor ratio) / (10 x concentration (%) of stock solution)

Or,

Required amount of solution (mls) = {Required amount (%) x Weight of substrate x Liquor ratio} / {Concentration (%) of stock solution}

**Example of Dyeing Calculation: **

**Recipe: **

**Dyes: **

- Rema Blue RR = 1.122%
- React Red KHW = 2.014%
- React Yellow KHW = 1.486%

Salt = 70%

Soda Ash (concentration.20%) = 5 gram/liter

Caustic Soda = 1.32%

M: L = 1:8

Sample Weight. = 5 gram

Stock Solution (In percentages) = 1

Therefore, recipe calculation for dyes and auxiliaries in gram/liter will be as follows:

**For dyes: **

We know,

**Required Dye = (Shade percentage (%) x Weight of the fabric in gram (gm)/percentage (%) of Stock solution. **

Calculation of dyestuff will be,

for,

- Rema Blue RR = (1.12 2x 5)/1=5.61 g/l
- React Red KHW = (2.014 x 5)/1= 10.07 g/l
- React Yellow KHW = (1.486 x 5)/1= 7.43 g/l.

**For auxiliaries: **

We know,

**Salt in gram/liter = (Required amount (%) x Sample weight x Liquor Ratio) / 1000 **

Required Salt = (70 x 5 x 8)/1000 = 2.8 gram.

For Soda ash (concentration 20%) :

We know ,

Required amount of solution (mls) = (Gram/liquor required x Weight of substrate x Liquor ratio ) / (10 x concentration (%) of stock solution)

Required amount of soda ash in C.C. = (5 x 5 x 8) / (10 x 20) = 1.0

Extra Water required:

= M:L – (required water to make solution of dyes & auxiliaries) = (5 x 8) – [(5.61+10.07+7.43) + (1.0+0.12) ]

= 40 – 24.112

= 15.77 (Salt is added in solid form)

Author of this Article:S. M. Hossen UzzalB.Sc. in Textile Technology Noakhali Textile Engineering College Email: [email protected]

Excellat

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