Some Tips and Tricks:
Use warm water 
Be sure to pour the nail polish CLOSE to the surface, so it doesn't sink. You want to create a film on the top of the water that the nail polish floats on when you pour. Then use the toothpick to create your pattern
You have to act fast. Don't wait too long or the film will become a bit gloopy or thick and is more likely to cause bubbles
Do a roll-dip of your mug into the nail polish to capture the pattern. Only dip or roll ONCE, or wait for it to completely dry before dipping again to avoid bubbles
Leave it to dry completely before sealing it with a dishwasher safe mod lodge. 
If making a mug- do not dip it anywhere that will come in contact with someone's lips (only dip the bottom of the mug)

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