The candies converter
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"When activated in your candy box, this surprising object quickly converts all your candies into lollipops. One candy gives one lollipop !"
The candies converter is an unlockable item in Candy Box. It is accessed by completing the Castle's stairs quest. It allows conversion of candies into lollipops on a one-to-one basis. 

The rate at which the conversion occurs speeds up over time, so long as you leave it running.

from candiesConverter.js:

// We increment the speed
if(this.speed < 10000) this.speed += 1;
else this.speed *= 2;