non conductive material inspection - ultrasound, xray, ?

Could someone suggest any instrumentation to internally view non conductive material? Example : Validate a centered wick in a candle internally.

Thanks

Looks like a tough application to solve. At first I was thinking of a capacitive proximity sensor and adjust to sense the wick, but you are looking to see if the wick is centered.
Is there other places to sense the product as it is being assembled, instead of the final product?

Seeing if the wick is centered on top and on the bottom could be done with a vision application. But really this is a toughy. Obviously, I don't know any specifics about the application and setup, but I would suggest attempting to make the quality control for the wick placement happen before the wax was added.

An ultrasonic or radar scanner would be able to detect a density change.
I would think the wick would be a different density then the surrounding material
You may have to rotate the part within the scanner to determine if the wick is centered