Which type of buffing pad is used last when machine compounding a finish?

The correct choice is foam, as foam pads are commonly used as the final buffing pad in the machine compounding process. Foam pads are designed to achieve a high-gloss finish and are effective at polishing the surface after the initial compounding steps. They have varying levels of density and softness, which allows for different polishing and finishing capabilities, providing a smooth, reflective surface.

During the compounding process, coarser materials like wool or more aggressive pads may be used initially to remove imperfections or heavy oxidation. In contrast, foam pads are more gentle and specifically suited for achieving a final polish. This makes them an ideal choice for that last step, as they effectively enhance the clarity and depth of the paint finish.

The other types of pads, such as wool, microfiber, and felt, serve different purposes in the compounding and polishing sequence. Wool pads, for instance, are excellent for cutting and removing deeper scratches due to their aggressive nature, while microfiber pads can be helpful for initial polishing or can be employed in various stages but are generally less common for the final finish compared to foam pads. Felt pads can also be used for polishing, particularly in specific applications, but foam remains the preferred choice for that final touch on a glossy finish.