How does using mat affect the print-thru on the surface of a composite?

Using mat in composite manufacturing plays a key role in controlling print-thru, which refers to the visibility of underlying fabric patterns or other surface imperfections through the final layer of resin or gelcoat. The primary reason the correct answer is that it decreases print-thru is due to the way mat disperses resin and provides a more uniform surface texture.

Mat, typically made of chopped strands of glass fibers, creates a denser layer that helps to fill in the spaces between the underlying woven fabric layers. This denser structure minimizes the likelihood of light passing through and highlighting any irregularities or patterns in the layers beneath. As a result, the surface becomes smoother and more uniform, thereby reducing the visual impact of print-thru.

In addition, when mat is utilized, it can also help to break up the continuity of the weave of any fabric beneath it, further preventing shadows and outlines that could lead to noticeable print-thru on the finished surface. Thus, the incorporation of mat is a common technique to achieve a higher-quality appearance in composite materials.