The FDM printing process naturally leaves a sheen on the printed part which will be somewhat glossy/reflective. This can be greatly enhanced by acetone post-processing!
https://all3dp.com/2/abs-smoothing-a-beginners-guide-to-abs-vapor-smoothing/
Most of our filaments are "opaque" - but depending on wall thickness, there may be some light transmission. The best approach to neutralize this effect would be to use a primer and multiple coats of a dark paint to create a fully opaque barrier on the exterior of the part
https://www.makerbot.com/professional/post-processing/painting/
