This is to prevent your metal from rusting in the following steps.
Use 2 cups boiling water and 1 tablespoon vinegar per bowl.
Add enough food color as the color somewhat fades when the clothespins dry.
This step might take a couple of days.
Mix and match your clothespins for different coaster designs.
Repeat with several shades of the color of your choice. Also roll up balls of white, translucent and pearl white.
Freeze the balls for 10 to 30 minutes.
Gather a bit of white, translucent, and shimmery white and mix them without mushing them together.
Gather more piles of three colors and mix without mushing them. Repeat until you have 8-10 ball combinations.
Roll the colorful balls between parchment or wax paper into thin layers.
Take the light balls you made before and wrap the flat colorful layers around them.
Repeat this until all layers have been used up and you have a large hockey puck looking shape.
Roll a chunk of gold clay into a ball and then flatten. Wrap the gold around the "puck".
Roll the slices out in all directions to create the shape you wish for your coasters.
Preheat your oven to 275°F and place your slices on a piece of parchment paper atop a tray.
After the slices cooled, brush a layer of Mod Podge dimensional magic on top for a nice "agate" like shine.
Chose coasters with a cork on the bottom to protect surfaces, or just put sticker felt onto the bottom.
Use fabric, a photo, printed design on photo paper etc. Regular paper is not a good choice as you will get bubbles.
Repeat a few coats to protect and seal the project - don't forget the sides of the coaster and paper. Let dry between each coat.
You can also use a few layers of clear top coat nail polish, letting it dry between each coat.
After you paint all your coasters, you will see tiny bubbles in the resin. Use a lighter to get rid of them.