diff --git a/_manual/07_working-with-sessions/10_cleaning_up.html b/_manual/07_working-with-sessions/10_cleaning_up.html
index 63cb5bee..9aa16f08 100644
--- a/_manual/07_working-with-sessions/10_cleaning_up.html
+++ b/_manual/07_working-with-sessions/10_cleaning_up.html
@@ -27,17 +27,20 @@ title: Cleaning up Sessions
 
 <p>Ardour represents audio waveforms with peak files, that are graphical images generated from the
   sound files. This generation can be time and CPU consuming, so it uses a cache of the generated
-  images to speed up the display process.
+  images to speed up the display process. To watch for files modification, Ardour relies on the file-modification 
+  time. If an external file is embedded in the session and that file changes, but the system-clock is skewed 
+  or it is stored on an external USB disk (VFAT), Ardour can't know the change happend, and will still use its 
+  deprecated peak files.
 </p>
 
-<p>Using the <kbd class="menu">Reset Peak Files</kbd> menu allows to reset this cache, which frees up disk space.
-  note, though, that displaying waveforms requires these peak files, so they'll be recreated by Ardour, 
-  consuming CPU and time. It can prove useful if some waveforms are not used anymore, or if a graphical glitch happens.
+<p>Using the <kbd class="menu">Reset Peak Files</kbd> menu allows to reset this cache, which frees up disk space,
+  and forces the re-creation of the peak files used in the session. It can prove useful if some waveforms 
+  are not used anymore, or if a graphical or time glitch happens.
 </p>
 
 <h2>Clean-up Unused Sources...</h2>
 
-<p>Recording usually lefts behind a lot of unused takes, be it in midi or audio form, that can clutter
+<p>Recording usually lefts a lot of unused takes behind, be it in midi or audio form, that can clutter
   the Region List, and eat up a lot of hard drive space. While its generally a good practice to keep as
   many things as possible while recording, when transferring or archiving the session, some clean up can
   help a lot in reducing the sessions clutter and size.
@@ -51,7 +54,7 @@ title: Cleaning up Sessions
 
 <h2>Flush Wastebasket</h2>
 
-<p>Although Ardour is a <em>non-destructive</em> audio-editors, it allows for a very careful destruction of unused media materials.
+<p>Although Ardour is a <em>non-destructive</em> audio-editor, it allows for a very careful destruction of unused media materials.
   This function is closely linked to the previous one. When the unused sources have been cleaned up and quarantined, the 
   <kbd class="menu">Flush Wastebasket</kbd> menu will allow for their physical destruction.
 </p>