When you expand a portfolio item on the homepage, no sharing buttons are visible.
This is by design. Because of how the expander works, the scripts and functions that drive the sharing buttons would cause too much additional load and potentially not work if we included them here. Sharing a specific portfolio post would also target traffic back to a confusing view of the portfolio rather than the intended view. You may use a Lightbox Plugin such as Responsive Lightbox, and the PrettyPhoto setting with social sharing enabled, which places sharing buttons in the lightbox for sharing of individual images. Be sure to discreetly watermark your images and enter titles and descriptions when uploading them for the best results when sharing to services such as Facebook or Pinterest.