I use an ultrasonic on about everything I restore. As noted, don't immerse the whole pen. Nib cleaning takes one or two 3 minute cycles. Power should be under 50W. I disagree with the quoted article's instructions to use warm water. No. Cool or room temperature, and don't use one with a heater in it. The water will heat on its own, and I like to keep the water cool. Too hot and it can damage the plastic. Use a full tank of water, or if you want put the cleaning solution in a plastic container and put that in the water in the tank. The energy will transfer to the solution.