First, I prepped the jars by washing them, removing the labels and drying them thoroughly.
Next step, use a sponge dipped in glass paint and apply all over the jar to create an even, speckled look. This is so that there'll be a background colour, but you could also skip this step if you have a very smooth, clean jar surface.
Now, you'll need some designs. There is lots of inspiration to be had on Pinterest, Youtube and on the net in general. Besides tutorials, you can also look at the kinds of decorations others have used on their tea-light jars. The easiest thing to do would be to download some mehndi designs from the net, and practice drawing them on paper first with a pen or pencil.
Finally, once you've identified your design and practiced drawing it, transfer the design onto your jar using a black glass painting pen (these are available at craft stores). The thinner the tip, the more elaborate the design you can pull off. I had to make do with simpler designs as I couldn't find a really thin-tipped pen :-)
It can be a bit challenging to draw on a surface that's not smooth or has already been painted on. One tip would be to make sure the ink is always flowing freely on your pen. If it feels like it's drying out, stop, shake the pen and test it on a piece of paper to get the ink flowing again.
If it's a tall jar, you'll need to put in a filler - stones, shells, marbles, dried spices, anything you fancy - before dropping in the tea light or else, the candle will just go out once it reaches the bottom of the jar! :-)
