Printing with Natural Dyes

Printing with Natural Dyes

In traditional methods in India, printing is essentially carried in three steps:

1. Preparation of the Cloth
2. Mordanting
3. Dyeing

1. First of all the cloth is prepared by applying tannin.

2. A thickened mordant is printed on this tannin treated cloth in the desired pattern.

3. The cloth is then dyed so that dyestuff attaches itself to those parts of the cloth to which mordant has been applied.

Thus the various processes are:

a. Tanning of fabric
b. printing of mordant
c. fixing of the modant
d. washing out the excess of fixing agent
e. dyeing
f. washing and soaping.

Harda or Myrobalan is used in India as a tanning agent for dyeing and printing with natural colours.

It is applied on scoured cotton fabric in cold ( 10-40 gpl) using conventional method of tub dip wherein the Harda powder is replenished with each piece added to the bath.

After drying various metallic salts such as alum or ferrous sulphate are printed on the fabric either separately or in mixtures.

It is then subsequently dyed with madder root ( Manjith), pometranate rind, kusum flowers and other vegetable dyes.

Trade Names of Natural Dyes

DYE SOURCE	BOTANICAL NAME/ SOURCE	TRADE NAME
Pomegranate	Punica granatium	Pacific
Myrobalan	Terminalia chebula	Kongo
Cutch	Acacia catechu	Thar
Kamala	Mallotus phillipinensis	Basant
Nut Galls	Quercus infectoria	Amber-M
Madder	Rubia cardifolia	Indus
Himalayan Rhubarb	Rheum emodi	Desert
Indigo	Indigofera tinctoria	Nile
Annato	Bixa orellana	Amazon
Lac	Coccus laccae	Rhine-M

You can find a tutorial on How to Use Natural Dyes here.  Receipes for natural dyes can be found here.

Common Causes of Dyeing Defects

Common Causes of Dyeing Defects:

It is important that the general precautions should be followed while dyeing a textile material. It is always helpful to keep a record of all the conditions (including temperature, time, conc of color, chemicals, material to liquor ratio) in order to get an even shade in each batch. In general the following are the common causes of dyeing defects across all the categories of dyes:

1. The material is not well prepared for dyeing and printing

a. Material having dead fibres or other defective fibres
b. Left over of Chemicals after bleaching etc.
c. Material not properly desized
d. Material not properly mercerised.
e. Absorbancy of the fabric not proper
f. Sticking of insoluble material on the fibres
g. Impurities are not removed properly
h. Uneven heat treatment.

2.Water Quality not Proper

a. More Hardness of water
b. Water has metal ions such as iron.
c. pH of water not proper
d. Water having more chlorine

3. Due to Shortcomings in making Dyeing Solution

a. Improper weight ratio of colors, material and chemicals.
b. Improper material to water ratio
3. Improper filtering of concentrated colors.

4. Due to Shortcomings in the dye machinery

a. Coming out of Dye liquor during dyeing
b. Defective instruments controlling temperature, pressure speed etc.

Polyethylene Fibres

Polyolefin fibres

Fibres made from polymers or copolymers of olefin hydrocarbons such as ethylene, propylene are called polyolefins.

Polyethylene: Of all the fibre forming polymers, polyethylene (made by addition polymerisation) Ch2==Ch2 has the simplest structure.

Manufacture: Ethylene is the principal raw material for producing polyethylene fibres. Ethylene gas is obtained by cracking petroleum.

Polymerisation: Ethylene is polymerised under severe conditions in autoclaves at 200 deg C and 1500 atmospheric pressure in the presence of traces (0.01%) of oxygen acting as a catalyst. The polymer resembles paraffin wax and is characterised by low density.

Spinning : Spinning of polyethylene is carried out by melt spinning. The polymer with a molecular weight of about 15,000 is spun from the melt at about 205 deg C and extended through a spinnerette of 0.1 mm diameter into a current of cooling gas. The filaments are cooled to 15 -60 deg C and stretched 4 to 10 times their original length. The drawn monofilaments are wound on spools.

Properties of polyethylene

a. Polyethylene fibre has a round cross section and has a smooth surface. Fibres made from low molecular weight polyethylene have a grease like handle.

b. Specific Gravity- 0.92
Tenacity - 1.0-1.5 gpd
Elongation at Break %- 45-50
Tensile Strength psi - 15000
Softening Range: deg C- 85-90

c The moisture regain of polyethylene is practically nil and hence moisture does not affect the mechanical properties of the fibres.

d. Polyethylene is insoluble in most of the common organic solvents at room temperature.

e. Polyethylene fibres have a high degree of resistance to acids and alkalies at all concentrations even at high temperature.

f. The fibre is generally inert and is resistant to wide range of chemicals at ordinary temperatures. They are attacked by oxidising agents.