There are two techniques how batik patterns can be produced. On the one hand wax is used to protect parts of a material of coming in contact with a dye. This is the traditional way which is widely used in Java, the main island of Indonesia and the origin of batik.
On the other hand knots are used to achieve the same effect. Because this is simpler we want to try this first.

Required: white T-shirt, beaker 1-liter, Indanthren dye (a vat dye, various types and colours), sodiumhydroxide solution (32 %), sodiumdithionite

First You should take a rope and put some knots into the shirt. Fix them very tightly to avoid any contact with the dye.

For one shirt or 100 [g] of cotton material weigh 2 [g] of the Indanthren dye and add them to the beaker containing 200 [ml] of aqua dest. with a temperature of 50 [°C].
Stir for dispersion and add 30 [ml] of 32% NaOH-solution and another 10 [g] of sodiumdithionite (evtl. “Hydrosulfit BASF”).
Add the shirt and allow to dye for ca. 20 minutes. Casually move the shirt. If necessary add more water.
Remove the shirt from the solution and wash thoroughly in cold water.
Allow reoxidation at the air for ca. 5 minutes. Then wash again with 50 [°C] water containing soap (or soda).
Finally remove the knots.