Is ist possible to get the page variables in node templates? I set a variable by implementing the hook hook_preprocess_page. The variable is available in $variables['my_custom_var'] within the page.tpl.php. 

Is it possible to get access to this variable in node.tpl.php or any other node template?
In node.tpl.php you can render the particular field like this:

echo render($content['field_header']);
hide($content['field_header']); // This line isn't necessary as the field has already been rendered, but I've left it here to show how to hide part of a render array in general.


If you need to do this in page.tpl.php then you want to implement a preprocess function in your template file to get the variable you need:

function mymodule_preproces_page(&amp;$vars) {
  if ($node = menu_get_object() &amp;&amp; $node-&gt;type == 'page') {
    $view = node_view($node);
    $vars['my_header'] = render($view['field_header']);
  }
}