WP_Query and next_posts_link

I cannot figure out how to make next_posts_link() work within my custom WP_Query. Here is the function:

function artists() {
  echo '<div id="artists">';
  $args = array( 'post_type' => 'artist', 'posts_per_page' => 3, 'paged' => get_query_var( 'page' ));
  $loop = new WP_Query( $args );
  while ( $loop->have_posts() ) : $loop->the_post();
    echo '<a class="artist" href="'.get_post_permalink().'">';
    echo '<h3 class="artist-name">'.get_the_title().'</h3>';
    $attachments = attachments_get_attachments();
    $total_attachments = count( $attachments );
    for( $i=0; $i<$total_attachments; $i++ ) {
      $thumb = wp_get_attachment_image_src( $attachments[$i]['id'], 'thumbnail' );
      echo '<span class="thumb"><img src="'.$thumb[0].'" /></span>';
    }
    echo '</a>';
  endwhile;
  echo '</div>';
  next_posts_link();
}

Can anyone tell me what I am doing wrong?

Thanks

try passing max_num_pages to the function:

next_posts_link('Older Entries »', $loop->max_num_pages);