Here is a very brief description of how I do batik on cotton.
There are many other “systems,” but all include the use of wax to resist dye.

Planning:

First a design is drawn with pencil or charcoal on the back of white cotton. Then the cotton is stretched on wooden stretcher bars in preparation for waxing.

Waxing:

Next, a molten mixture of beeswax and paraffin is painted, spattered, stamped, or otherwise applied to any areas where the silk is to remain white. The first waxing is done from the back, following the drawing. The next waxing is done from the front, to give a full resist.

Dyeing:

The stretched cotton is dampened with a soda ash solution and the lightest color of dye is brushed on with Chinese hake brushes. The first dye may be applied as a wash, similar to watercolor. The dyed cloth must be kept damp overnight at a temperature between 75 and 90 degrees Farenheit so that the fiber-reactive dyes become permanent. This process is called batching.

In the morning, the cotton is rinsed in cool water to remove any soda ash, dried, and restretched.

Repeat the above 2 steps up to 20 times...

Then, wax is applied to areas which are to remain this color, and the next darker dye is applied. Each color is affected by the color it goes over: turquoise over yellow makes green, etc. Each layer of dyeing and waxing takes one day. Many of my cotton pieces require up to 20 layers, so the process may take several weeks for only one piece.

The last dyeing is usually the darkest color. Anywhere the wax has cracked, the dye penetrates, forming dark lines called crackle. Sometimes I use it, sometimes not.

Finishing the batik painting:

Finally, the cotton is dipped in boiling water to remove the wax, and the piece is then washed, ironed, and sewn to acid-free foam core mounting board. An acid-free double mat covers the stitches, and the piece is framed under ultraviolet-screening glass.

Fine art should never be hung in direct sunlight.

See detailed information on the batik process by Paula Burch.