Years ago, my co-pilot and I were flying a Beech 90 at FL220 and encountered moderate icing. ATC granted our request for FL240, where we found lighter ice, but we decided to try FL200 in an attempt to exit the icing. The icing was again moderate at FL200. FL180 was not available due to the altimeter setting, and we did not have quick-donning oxygen masks to go above FL250, so we decided that the light icing at FL240 was our best option. My co-pilot prepared to radio ATC:
"The controller is going to be mad at you if you ask him to go back to where we were."
"No, he won't be mad at me."
[Co-pilot calls ATC.]
"Tower, the captain wants to go back to 240."